Publisher：Rsc Advances  

Nickel catalysts supported on nanocrystalline CeO<inf>2</inf> exhibit intriguing properties, including high Ni dispersion, a high concentration of lattice oxygen defects in the support, and facile formation of hydroxyl groups on the Ni surface. In an electric field, CO<inf>2</inf> methanation was carried out using a Ni/CeO<inf>2</inf> catalyst. The reaction occurred even at around 393 K, a low temperature at which no activity was observed under conventional thermal conditions. In the CO<inf>2</inf> methanation environment, the amount of surface OH groups increased when an electric field was applied. Furthermore, adsorption species like hydroxy carbonyl, which were not detectable without the electric field, were identified. These findings suggest that applying an electric field influences the interface between Ni nanoparticles and CeO<inf>2</inf> particles, promoting the formation of oxygen vacancies and OH species on the Ni/CeO<inf>2</inf> catalyst. This enhances CO<inf>2</inf> activation, allowing the reaction to proceed at lower temperatures.

DOI： 10.1039/d5ra08683c

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PubMed

Publisher：Chemistry Letters  

Oxidative coupling of methane reaction in an electric field at low temperatures was investigated using alkaline-earth-metal-cation-doped LaAlO<inf>3</inf> perovskite catalysts. Results demonstrate that reaction activity depends on the amount of surface oxygen species on the perovskite phase, which are activated by direct current applied to the catalysts and function as active sites, selectively promoting C<inf>2</inf> production rather than the complete oxidation of methane.

DOI： 10.1093/chemle/upag005

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Publisher：Chemistry Letters  

Ammonia is attracting attention as a carbon-free hydrogen carrier with high hydrogen content and good handling properties, although its endothermic decomposition requires high temperatures (>773 K). We previously achieved nearly complete ammonia conversion even at 398 K via an electric field (EF)-assisted catalytic reaction, in which hydrogen conduction on the catalyst surface (i.e., surface protonics) plays a key role. This study reveals a clear correlation between the catalyst's hydrogen adsorption capacity and EF-assisted ammonia decomposition activity. Mechanistic analyses suggest that enhanced hydrogen transfer from Ru to a support with high hydrogen adsorption capacity promotes surface proton conduction, thereby improving catalytic activity under an EF.

DOI： 10.1093/chemle/upag016

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Publisher：Applied Catalysis A General  

Supported metal catalysts play an important role in various chemical reactions, including hydrogenation and dehydrogenation. Their activity and selectivity depend on factors such as the metal particle size and surface area and interaction between the metal and the support. Among these factors, “strong metal-support interaction” (SMSI) is a phenomenon by which metal particles supported on an oxide support are embedded under high-temperature reduction conditions, causing important changes in their surface adsorption properties and electronic states. Such electronic state changes reportedly alter the d-band centers of the metal and the adsorption energy of intermediates, thereby strongly influencing catalytic performance. For this study, we investigated SMSI effects on the selective hydrogenation of 4-chloronitrobenzene (4-ClNB) to 4-chloroaniline (4-ClAN) using a Pd/TiO<inf>2</inf> catalyst. This reaction requires reduction of the -NO<inf>2</inf> group while preventing dissociation of the -Cl group. Actually, Pd catalysts are known to have high reducing activity toward the -NO<inf>2</inf> group, but they also cause undesirable C-Cl bond dissociation, which reduces their selectivity. By contrast, we found that controlling the electronic state of Pd via SMSI can enhance the selectivity to 4-ClAN. The underlying mechanisms were elucidated using TPR, TEM, CO adsorption, DRIFTS, XAFS, XPS, and DFT calculation.

DOI： 10.1016/j.apcata.2025.120540

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Publisher：Journal of Physical Chemistry C  

Fluorite-type CeO<inf>2</inf>was examined as an oxygen carrier material for the chemical looping reverse water–gas shift (RWGS-CL) for effective conversion of CO<inf>2</inf>to CO, and potential dopants to enhance its redox properties were explored through a combination of theoretical calculations and experimental investigations. A strong correlation was observed between the oxygen vacancy formation energy, calculated using neural network potential (NNP) calculations, and the experimentally determined reduction rate under a H<inf>2</inf>atmosphere, leading to the identification of praseodymium (Pr) as a promising dopant. The redox performance of Pr-doped CeO<inf>2</inf>improved with increasing doping ratio, with Ce<inf>0.67</inf>Pr<inf>0.33</inf>O<inf>2</inf>exhibiting the highest CO<inf>2</inf>splitting capacity. In situ X-ray absorption fine structure (XAFS) analysis confirmed that Pr doping promotes the Ce⁴⁺↔ Ce³⁺redox cycle during the RWGS-CL process at 773 K. Furthermore, NNP-based calculations revealed that Pr doping induces a positive shift in the charge of Ce atoms, thereby enhancing the redox capacity of the Pr-doped system.

DOI： 10.1021/acs.jpcc.5c04849

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Publisher：ACS Catalysis  

Modified In<inf>2</inf>O<inf>3</inf> has the potential to be a better oxygen storage material due to its readily reducible surface and abundant bulk lattice oxygen released with a marked valence change from In³⁺ to In⁰. This work describes that In<inf>2</inf>O<inf>3</inf> modified with a Ni-Cu alloy supports a chemical looping system consisting of oxidative dehydrogenation of ethane and CO<inf>2</inf> splitting at the low temperature of 873 K with a large oxygen capacity (>4 wt %). This reaction system is achieved through dynamic changes between Ni-Cu binary alloy and Ni-Cu-In ternary alloy associated with the redox of indium species. Meticulous material screening, characterization, and theoretical calculations have revealed that the Ni-Cu alloy promotes the redox of In<inf>2</inf>O<inf>3</inf> by activating ethane and by incorporating reduced indium species.

DOI： 10.1021/acscatal.4c07737

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Publisher：Catalysis Science and Technology  

The elimination of unburned methane produced by internal combustion engines is extremely important because of the strong greenhouse effect of methane. Difficulties in controlling unburned methane arise from its characteristics, such as its difficulty of adsorption, low exhaust gas temperatures in an efficient engine, low concentrations of unburned emitted methane, and the coexistence of steam and residual oxygen as coexisting substances in the exit gas. Results of the present study demonstrate that the removal activity of methane by complete combustion was improved dramatically at low temperatures by the application of a DC electric field to the Pd/Ce<inf>x</inf>Zr<inf>1−x</inf>O<inf>2</inf> catalyst system, even under a humid atmosphere. Specifically, 1 wt% Pd/Ce<inf>0.25</inf>Zr<inf>0.75</inf>O<inf>2</inf> showed very higher methane conversion under humid conditions than under dry conditions at 473 K in the presence of an electric field. To elucidate the reaction mechanisms involved in this process of steam adsorption, we conducted partial pressure dependence tests and activity tests with steam under an electric field.

DOI： 10.1039/d4cy00699b

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Publisher：Chemical Science  

Ammonia, which can be decomposed on-site to produce CO<inf>2</inf>-free H<inf>2</inf>, is regarded as a promising hydrogen carrier because of its high hydrogen density, wide availability, and ease of transport. Unfortunately, ammonia decomposition requires high temperatures (>773 K) to achieve complete conversion, thereby hindering its practical applicability. Here, we demonstrate that high conversion can be achieved at markedly lower temperatures using an applied electric field along with a highly active and readily producible Ru/CeO<inf>2</inf> catalyst. Applying an electric field lowers the apparent activation energies, promotes low-temperature conversion, and even surpasses equilibrium conversion at 398 K, thereby providing a feasible route to economically attractive hydrogen production. Experimentally obtained results and neural network potential studies revealed that this reaction proceeds via HN-NH intermediate formation by virtue of surface protonics.

DOI： 10.1039/d4sc04790g

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Publisher：Catalysis Science and Technology  

Nitrous oxide (N<inf>2</inf>O) exerts strong effects on global warming and environmental destruction. Various catalytic technologies have been investigated for N<inf>2</inf>O abatement. We investigated a catalytic system in an electric field, revealing that N<inf>2</inf>O can be decomposed efficiently, even at low temperatures and in the presence of excess oxygen and water vapour. Reaction mechanisms with and without an electric field have been investigated using kinetics and various operando analyses, which revealed that surface-lattice oxygen on catalyst supports plays a crucially important role in N<inf>2</inf>O decomposition in an electric field at low temperatures.

DOI： 10.1039/d4cy00698d

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Publisher：Catalysis Science and Technology  

Chemical looping dry reforming of CH<inf>4</inf>, a promising approach to reduce fossil fuel consumption and use CO<inf>2</inf>, hinges on designing an efficient oxygen carrier. However, high operating temperatures and unsatisfactory performance hamper its application. Loading a small amount of Ru promoter on the La<inf>2</inf>Ce<inf>2</inf>O<inf>7</inf> oxygen carrier enhances CH<inf>4</inf> activation considerably, lowering the onset temperature to around 545 K. The Ru/La<inf>2</inf>Ce<inf>2</inf>O<inf>7</inf> material exhibited impressive performance, achieving CH<inf>4</inf> conversion of around 65%, with almost negligible CO<inf>2</inf> produced during the reduction step and CO<inf>2</inf> conversion exceeding 95% during the CO<inf>2</inf> re-oxidation step over 10 redox cycles. Despite slight carbon deposition, the redox performance remains stable because of efficient carbon removal in the reoxidation step and the inherent structure stability of the oxygen carrier. This superior performance is attributed to the strong metal-support interaction between Ru and La<inf>2</inf>Ce<inf>2</inf>O<inf>7</inf>, forming Ru-O-Ce bonds at the Ru^δ+-CeO<inf>2−x</inf> interface. These bonds anchor active Ru onto stable La<inf>2</inf>Ce<inf>2</inf>O<inf>7</inf> with excellent oxygen-ionic conductivity, enhancing CH<inf>4</inf> activation by increasing surface oxygen vacancies and maintaining structural stability with well-dispersed Ru promoters during cycles. Moreover, the migration of O²⁻ in subsurface is promoted by creating an elevated oxygen chemical potential gradient induced by the oxygen-deprived surface, facilitated by the Ru promoter.

DOI： 10.1039/d4cy00450g

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Publisher：Sustainable Energy and Fuels  

Ammonia synthesis is crucial for fertiliser production, future hydrogen storage, and hydrogen carrier production. Herein, we present a novel ammonia synthesis system using an iron phosphide catalyst with a DC electric field. Under mild reaction conditions (i.e., 400-430 K and 0.1 MPa of H<inf>2</inf>), the air-stable iron phosphide catalyst exhibits superior performance to the conventional, unstable iron catalysts. Furthermore, this catalyst system enables precise control over ammonia production through on/off-switching of the DC electric field, demonstrating its potential for more dynamic and responsive synthesis processes. The structure-activity relationship of this catalytic system was also explored using various techniques such as TEM observation, XAFS analysis, and theoretical calculations. These findings open up promising avenues for the future development of next-generation on-site and low-temperature ammonia synthesis technologies that can be operated on demand.

DOI： 10.1039/d4se00109e

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Publisher：Rsc Advances  

Ammonia is an extremely important storage and transport medium for renewable energy, and technology is expected to produce it on demand and onsite using renewable energy. Applying a DC (direct current) to a solid catalyst layer with semiconducting properties makes ammonia synthesis highly efficient, even at low temperatures (approximately 400 K). In this process, oxide supports with semiconducting properties play important roles as metal supports and conduction fields for electrons and protons. The influence of the degree of particle aggregation on the support properties and ammonia synthesis using an electric field was evaluated for CeO<inf>2</inf>, which is the best material for this purpose because of its semiconducting properties. The results showed that controlling the aggregation structure of the crystalline particles could significantly influence the surface conductivity of protons and electrons; thus, the activity could be largely controlled. The Ru–CeO<inf>2</inf> interaction could also be controlled by changing the crystallinity, which suppressed the aggregation of the supported Ru and significantly improved the ammonia synthesis activity using an electric field at low temperatures.

DOI： 10.1039/d4ra01457j

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Publisher：Chemical Communications  

Lean-burn engines are gaining attention for their lower CO<inf>2</inf> emissions, higher thermal efficiency, and improved fuel economy compared to traditional combustion engines. However, they present some difficulty for reducing nitrogen oxides (NO<inf>x</inf>) because of residual oxygen. To address this difficulty, NO<inf>x</inf> storage reduction (NSR) system, which combines noble metals and NO<inf>x</inf> adsorbents, is developed as a viable approach. But it requires cyclic operation, which adversely affects fuel efficiency. A novel approach proposed in this work is electric field-assisted lean NO<inf>x</inf> reduction, which applies an electric field to the NSR catalyst during lean conditions. This innovation uses surplus vehicle electricity for exhaust purification, enhances hydrogen transfer, and improves NO<inf>x</inf> reduction, even at low temperatures. Tests with a 3 wt% Pt-16 wt% BaO/CeO<inf>2</inf> catalyst demonstrate markedly higher NO<inf>x</inf> conversion to N<inf>2</inf> (13.1% vs. 2.9% without an electric field). This process is effective with extended electric field exposure, doubling the conversion rate. Electric field-assisted lean NO<inf>x</inf> reduction, by improving NSR technology, can enhance NO<inf>x</inf> conversion efficiency, reduce emissions, and optimize fuel efficiency in lean-burn engines.

DOI： 10.1039/d3cc05189g

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Publisher：Chemical Communications  

Reverse water gas shift (RWGS) can convert CO<inf>2</inf> into CO by using renewable hydrogen. However, this important reaction is endothermic and equilibrium constrained, and thus traditionally performed at 900 K or higher temperatures using solid catalysts. In this work, we found that RWGS can be carried out at low temperatures without equilibrium constraints using a redox method called chemical looping (CL), which uses the reduction and oxidation of solid oxide surfaces. When using our developed MGa<inf>2</inf>O<inf>x</inf> (M = Ni, Cu, Co) materials, the reaction can proceed with almost 100% CO<inf>2</inf> conversion even at temperatures as low as 673 K. This allows RWGS to proceed without equilibrium constraints at low temperatures and greatly decreases the cost for the separation of unreacted CO<inf>2</inf> and produced CO. Our novel gallium-based material is the first material that can achieve high conversion rates at low temperatures in reverse water gas shift using chemical looping (RWGS-CL). Ni outperformed Cu and Co as a dopant, and the redox mechanism of NiGa<inf>2</inf>O<inf>x</inf> is a phase change due to the redox of Ga during the RWGS-CL process. This major finding is a big step forward for the effective utilization of CO<inf>2</inf> in the future.

DOI： 10.1039/d3cc02399k

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DOI： 10.1246/cl.230032

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Publisher：Jacs Au  

Quantum annealing has been used to predict molecular adsorption on solid surfaces. Evaluation of adsorption, which takes place in all solid surface reactions, is a crucially important subject for study in various fields. However, predicting the most stable coordination by theoretical calculations is challenging for multimolecular adsorption because there are numerous candidates. This report presents a novel method for quick adsorption coordination searches using the quantum annealing principle without combinatorial explosion. This method exhibited much faster search and more stable molecular arrangement findings than conventional methods did, particularly in a high coverage region. We were able to complete a configurational prediction of the adsorption of 16 molecules in 2286 s (including 2154 s for preparation, only required once), whereas previously it has taken 38 601 s. This approach accelerates the tuning of adsorption behavior, especially in composite materials and large-scale modeling, which possess more combinations of molecular configurations.

DOI： 10.1021/jacsau.3c00018

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Publisher：Ees Catalysis  

The reverse water–gas shift (RWGS) reaction, a promising carbon-recycling reaction, was investigated by applying an electric field to promote the reaction at a temperature of 473 K or lower. The highly dispersed Ru/ZrTiO<inf>4</inf> catalysts with an approximately 2 nm particle size of Ru showed high RWGS activity with a DC electric field below 473 K, whereas CO<inf>2</inf> methanation proceeded predominantly over catalysts with larger Ru particles. The RWGS reaction in the electric field maintained high CO selectivity, suppressing CO hydrogenation into CH<inf>4</inf> on the Ru surface by virtue of promoted hydrogen migration (surface protonics). The reaction mechanisms of the non-conventional low-temperature reverse water gas shift reaction were investigated and revealed using various characterization methods including in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements. With the DC electric field, the reaction proceeds via a redox reaction where the generated oxygen vacancies are involved in CO<inf>2</inf> activation at low temperatures. As a result, the electric field promotes both hydrogen migration and redox reactions using lattice oxygen/ vacancies, resulting in high RWGS activity and selectivity even at low temperatures.

DOI： 10.1039/d2ey00004k

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Publisher：Rsc Advances  

Dry reforming of methane (DRM) is a promising reaction able to convert greenhouse gases (CO<inf>2</inf> and CH<inf>4</inf>) into syngas: an important chemical feedstock. Several difficulties limit the applicability of DRM in conventional thermal catalytic reactions; it is an endothermic reaction that requires high temperatures, resulting in high carbon deposition and a low H<inf>2</inf>/CO ratio. Catalysis with the application of an electric field (EF) at low temperatures can resolve these difficulties. Synergistic effects with alloys have also been reported for reactions promoted by the application of EF. Therefore, the synergistic effects of low-temperature DRM and Ni-Fe bimetallic catalysts were investigated using various methods and several characterisations (XRD, XPS, FE-STEM, etc.), which revealed that Ni-Fe binary catalysts show high performance in low-temperature DRM. In particular, the Ni<inf>0.8</inf>Fe<inf>0.2</inf> catalyst supported on CeO<inf>2</inf> was found to carry out DRM in EF effectively and selectively by virtue of its bimetallic characteristics.

DOI： 10.1039/d2ra05946k

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Publisher：Rsc Advances  

The effect of OH-groups on the surface of a Ni catalyst for low-temperature (473 K) steam reforming of methane in an electric field (EF) was investigated. Ni-doped YSZ (Zr<inf>0.65</inf>Y<inf>0.05</inf>Ni<inf>0.3</inf>O<inf>2</inf>) was chosen as a highly active catalyst for this purpose. The effects on catalyst activity of adding hydrogen and steam in the pre-treatment were assessed with and without EF. When an EF was applied, activity increased irrespective of the electronic state of Ni, whereas the metallic Ni state was necessary for activity without EF. Furthermore, the highest activity with EF was observed for the pre-treatment with a mixture of H<inf>2</inf> and H<inf>2</inf>O. Investigation of the superiority using XPS measurements showed an increase in the amount of Ni(OH)<inf>2</inf>, OH groups and H<inf>2</inf>O near the surface after the activity test, which are regarded as the reaction sites with EF. This finding suggests that a pre-treatment with steam increases the surface OH groups and Ni(OH)<inf>2</inf> on the Ni catalyst, and enhances surface proton conduction, thereby improving the activity.

DOI： 10.1039/d2ra04974k

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Publisher：Rsc Advances  

Catalytic ethane dehydrogenation (EDH) was investigated to improve the efficient production of ethylene, an extremely important chemical feedstock. The perovskite oxide YCrO<inf>3</inf> was found to be more suitable than earlier reported catalysts because it exhibits greater activity and C<inf>2</inf>H<inf>4</inf> selectivity (94.3%) in the presence of steam at 973 K. This catalyst shows the highest activity than ever under kinetic conditions, and shows very high ethane conversion under integral reaction conditions. Comparison with EDH performance under conditions without steam revealed that steam plays an important role in stabilizing the high activity. Raman spectra of spent catalysts indicated that steam prevents coke formation, which is responsible for deactivating YCrO<inf>3</inf>. Transmission IR and XPS measurements also revealed a mechanism by which H<inf>2</inf>O forms surface oxygen species on YCrO<inf>3</inf>, consequently removing C<inf>2</inf>H<inf>6</inf>-derived coke precursors rapidly and inhibiting coke accumulation.

DOI： 10.1039/d2ra04401c

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Publisher：Catalysis Science and Technology  

As automobiles increasingly become electrically driven and as more engines and motors are used together, the exhaust temperatures of internal combustion engines are decreasing. Further improvement of exhaust gas purification catalyst performance is necessary. To purify nitrogen oxides, unburned hydrocarbons, and carbon monoxide simultaneously at low temperatures, electrothermal heating and plasma catalysis have been proposed, but these methods require high power consumption. Results of this study indicate that a direct current electric field applied to a Pd-supported catalyst shows high purification rates even at temperatures lower than 473 K under TWC conditions (NO-CO-C<inf>3</inf>H<inf>6</inf>-O<inf>2</inf>-H<inf>2</inf>O). For clarifying the reaction mechanism in this process, the adsorption of reactants was evaluated using in situ DRIFTS measurements in an electric field. Factors that improve the activity at low temperatures in the electric field were clarified.

DOI： 10.1039/d2cy00129b

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Publisher：Chemical Communications  

CO<inf>2</inf> conversion to CO by reverse water-gas shift using chemical looping (RWGS-CL) can be conducted at lower temperatures (ca. 723-823 K) than the conventional catalytic RWGS (>973 K), and has been attracting attention as an efficient process for CO production from CO<inf>2</inf>. In this study, Co-In<inf>2</inf>O<inf>3</inf> was developed as an oxygen storage material (OSM) that can realize an efficient RWGS-CL process. Co-In<inf>2</inf>O<inf>3</inf> showed a high CO<inf>2</inf> splitting rate in the mid-temperature range (723-823 K) compared with previously reported materials and had high durability through redox cycles. Importantly, the maximum CO<inf>2</inf> conversion in the CO<inf>2</inf> splitting step (ca. 80%) was much higher than the equilibrium conversion of catalytic RWGS in the mid-temperature range, indicating that Co-In<inf>2</inf>O<inf>3</inf> is a suitable OSM for the RWGS-CL process.

DOI： 10.1039/d2cc00208f

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Publisher：Topics in Catalysis  

Considering the expansion of the use of renewable energy in the future, the technology to store and transport hydrogen will be important. Hydrogen is gaseous at an ambient condition, diffuses easily, and its energy density is low. So liquid organic hydrogen carriers (LOHCs) have been proposed as a way to store hydrogen in high density. LOHC can store, transport, and use hydrogen at high density by hydrogenation and dehydrogenation cycles. In this review, we will focus on typical LOHCs, methylcyclohexane (MCH), 18H-dibenzyltoluene (DBT), and 12H-N-ethylcarbazole (NECZ), and summarize recent developments in dehydrogenation catalytic processes, which are key in this cycle.

DOI： 10.1007/s11244-021-01452-x

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Publisher：Catalysis Science and Technology  

A Pd catalyst (Pd/Ce<inf>0.7</inf>Zr<inf>0.3</inf>O<inf>2</inf>) in an electric field exhibits extremely high three-way catalytic activity (TWC: NO-C<inf>3</inf>H<inf>6</inf>-CO-O<inf>2</inf>-H<inf>2</inf>O). By applying an electric field to the semiconductor catalyst, low-temperature operation of TWC can be achieved even at 473 K by virtue of the activated surface-lattice oxygen.

DOI： 10.1039/d1cy00591j

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Publisher：Chemical Communications  

It has over the last few years been reported that the application of a DC electric field and resulting current over a bed of certain catalyst-support systems enhances catalytic activity for several reactions involving hydrogen-containing reactants, and the effect has been attributed to surface protonic conductivity on the porous ceramic support (typically ZrO2, CeO2, SrZrO3). Models for the nature of the interaction between the protonic current, the catalyst particle (typically Ru, Ni, Co, Fe), and adsorbed reactants such as NH3 and CH4 have developed as experimental evidence has emerged. Here, we summarize the electrical enhancement and how it enhances yield and lowers reaction temperatures of industrially important chemical processes. We also review the nature of the relevant catalysts, support materials, as well as essentials and recent progress in surface protonics. It is easily suspected that the effect is merely an increase in local vs. nominal set temperature due to the ohmic heating of the electrical field and current. We address this and add data from recent studies of ours that indicate that the heating effect is minor, and that the novel catalytic effect of a surface protonic current must have additional causes.

DOI： 10.1039/d1cc01551f

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Publisher：Journal of Physical Chemistry C  

Introducing a catalyst for dehydrogenation of ethane (EDH) for steam cracking represents a promising solution with high feasibility to realize efficient ethylene production. We investigated EDH over transition-metal-doped CeO2 catalysts at 873 K in the presence of steam. Ce0.8Co0.2O2 exhibited high EDH activity and selectivity to ethylene (ca. 95%). In the absence of H2O, the catalytic activity dropped rapidly, indicating the promotive effect of H2O on ethylene formation. Catalytic experiments with water isotopes (D2O and H218O) demonstrated that EDH over Ce0.8Co0.2O2 proceeds through the Mars-van Krevelen (MvK) mechanism in which the reactive lattice oxygen in Ce0.8Co0.2O2 contributes to EDH. The consumed lattice oxygen was subsequently regenerated with H2O. X-ray diffraction and in situ X-ray absorption fine structure spectroscopy revealed that cobalt species were mainly present as CoO under EDH conditions and that redox between Co2+ and Co0 proceeded concomitantly with EDH. In contrast with Ce0.8Co0.2O2, no contribution of the lattice oxygen of CoO to EDH was verified in the case of CoO supported on α-Al2O3, which exhibited lower activity than Ce0.8Co0.2O2. Therefore, Co-CeO2 interactions are expected to play a crucially important role in controlling the characteristics of the reactive lattice oxygen suitable for EDH via the MvK mechanism.

DOI： 10.1021/acs.jpcc.1c02855

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Publisher：Physical Chemistry Chemical Physics  

Hydrogen (H) atom adsorption and migration over the CeO<inf>2</inf>-based materials surface are of great importance because of its wide applications to catalytic reactions and electrochemical devices. Therefore, comprehensive knowledge for controlling the H atom adsorption and migration over CeO<inf>2</inf>-based materials is crucially important. For controlling H atom adsorption and migration, we investigated irreducible divalent, trivalent, and quadrivalent heterocation-doping effects on H atom adsorption and migration over the CeO<inf>2</inf>(111) surface using density functional theory (DFT) calculations. Results revealed that the electron-deficient lattice oxygen (O<inf>lat</inf>) and the flexible CeO<inf>2</inf>matrix played key roles in strong adsorption of H atoms. Heterocations with smaller valence and smaller ionic radius induced the electron-deficient O<inf>lat</inf>. In addition, smaller cation doping enhanced the CeO<inf>2</inf>matrix flexibility. Moreover, we confirmed the influence of H atom adsorption controlled by doping on surface proton migration (i.e.surface protonics) and catalytic reaction involving surface protonics (NH<inf>3</inf>synthesis in an electric field). Results confirmed clear correlation between H atom adsorption energy and surface protonics.

DOI： 10.1039/d0cp05752e

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Publisher：Rsc Advances  

Hydrogen (H) atomic migration over a metal oxide is an important surface process in various catalytic reactions. Control of the interaction between H atoms and the oxide surfaces is therefore important for better catalytic performance. For this investigation, we evaluated the adsorption energies of the H atoms over perovskite-type oxides (Sr<inf>1−x</inf>Ba<inf>x</inf>ZrO<inf>3</inf>; 0.00 ≤x≤ 0.50) using DFT (Density Functional Theory) calculations, then clarified the effects of cation-substitution in the A-site of perovskite oxides on H atom adsorption, migration, and reaction. Results indicated local distortion at the oxide surface as a key factor governing H atom adsorption. Subtle Ba²⁺substitution for Sr²⁺sites provoked local distortion at the Sr<inf>1−x</inf>Ba<inf>x</inf>ZrO<inf>3</inf>oxide surface, which led to a decrement in the H atom adsorption energy. Furthermore, the effect of Sr²⁺/Ba²⁺ratio on the H atoms' reactivities was examined experimentally using a catalytic reaction, which was promoted by activated surface H atoms. Results show that the surface H atoms activated by the substitution of Sr²⁺sites with a small amount of Ba²⁺(x= 0.125) contributed to enhancement of ammonia synthesis rate in an electric field, which showed good agreement with predictions made using DFT calculations.

DOI： 10.1039/d1ra00180a

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Publisher：Chemical Science  

Efficient activation of CO<inf>2</inf>at low temperature was achieved by reverse water-gas shiftviachemical looping (RWGS-CL) by virtue of fast oxygen ion migration in a Cu-In structured oxide, even at lower temperatures. Results show that a novel Cu-In<inf>2</inf>O<inf>3</inf>structured oxide can show a remarkably higher CO<inf>2</inf>splitting rate than ever reported. Various analyses revealed that RWGS-CL on Cu-In<inf>2</inf>O<inf>3</inf>is derived from redox between Cu-In<inf>2</inf>O<inf>3</inf>and Cu-In alloy. Key factors for high CO<inf>2</inf>splitting rate were fast migration of oxide ions in the alloy and the preferential oxidation of the interface of alloy-In<inf>2</inf>O<inf>3</inf>in the bulk of the particles. The findings reported herein can open up new avenues to achieve effective CO<inf>2</inf>conversion at lower temperatures.

DOI： 10.1039/d0sc05340f

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Publisher：SAE Technical Papers  

To prevent global warming, further reductions in carbon dioxide are required. It is therefore important to promote the spread of electric vehicles powered by internal combustion engines and electric vehicles without internal combustion engines. As a result, emissions from hybrid electric vehicles equipped with internal combustion engines should be further reduced. Interest in catalytic reactions in an electric field with a higher catalytic activity compared to conventional catalysts has increased because this technology consumes less energy than other electrical heating devices. This study was therefore undertaken to apply a catalytic reaction in an electric field to an exhaust emission control. First, the original experimental equipment was built with a high voltage system used to conduct catalytic activity tests. Second, experiments with palladium cerium-zirconium oxide support catalysts showed that a three-way catalytic activity in an electric field could be found. at lower exhaust temperatures than conventional catalysts. Then it became clear that catalytic compositions that include semiconductor properties are a key for researching and developing this technology. In addition, applied electrical current control has been shown to be another focus of research and development. Finally, experimental results with several reducing species demonstrate that the electron-promoted surface proton and lattice oxygen greatly contributed to catalytic activity in an electric field.

DOI： 10.4271/2021-01-0573

Scopus

Publisher：Catalysis Today  

For future removal of NO<inf>x</inf> by catalysts, low-temperature NO reduction is desired. Results confirmed that a drastic improvement of catalytic activity by H<inf>2</inf>O on NO–CO–O<inf>2</inf> reaction over Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-</inf><inf>δ</inf> catalyst at the low temperature of 473 K or below. In a humidified condition, NO reaction with CO on Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-</inf><inf>δ</inf> proceeded without being affected by competitive adsorption of NO and CO, whereas that on Pd/Al<inf>2</inf>O<inf>3</inf> was inhibited by strong adsorption of CO on a Pd surface. From in-situ DRIFTS measurements, results showed that nitrite species on the support react with CO adsorbed onto Pd at the periphery of Pd particles and that carbonate species accumulated on Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-</inf><inf>δ</inf> are removed rapidly in a humidified condition. Although NO reduction proceeds dominantly on the Pd surface in a dry condition, supplied steam promotes desorption of the surface carbonate to advance the reaction of nitrite with CO for de-NO<inf>x</inf> in a humidified condition. This mechanism occurs specifically on Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-</inf><inf>δ</inf> by virtue of the lattice oxygen and oxygen vacancy on La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-</inf><inf>δ</inf>.

DOI： 10.1016/j.cattod.2019.10.025

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Scopus

Publisher：Catalysis Today  

Development of a highly efficient ammonia synthesis process is desirable for achieving a sustainable society. Regarding conventional heterogeneous catalysts, Ru-supported catalyst exhibits higher turn-over frequency (TOF) than Fe-supported or Ni-supported catalysts. However, we found that Fe-supported and Ni-supported catalysts show higher TOF than Ru-supported catalyst in an electric field at the low temperature of 373 K. Density functional theory (DFT) calculations revealed that N<inf>2</inf> dissociation through the “associative mechanism” plays a key role in the electric field. The ammonia synthesis activity in the electric field is determined by the N<inf>2</inf>H formation energy at the metal-support interface.

DOI： 10.1016/j.cattod.2018.10.055

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Scopus

Publisher：Journal of Physical Chemistry C  

For effective utilization of ethane in natural gas, catalytic dehydrogenation of ethane is a promising option that offers better efficiency than ethane cracking to produce ethylene, the most important fundamental chemical. Recently, it was reported that catalytic dehydrogenation of ethane proceeds effectively on doped perovskite oxide via the Mars-van Krevelen (MvK) mechanism. For this work, the reaction mechanism was investigated using density functional theory calculations. Results demonstrated that ethane activation over perovskite (La1-xBaxMnO3-δ) proceeds at the surface lattice oxygen coordinated with Ba, resulting in a low energy barrier of the C-H bond activation. Based on Bader charge analysis, the electron-deficient surface lattice oxygen, which is favorable for hydrogen abstraction from light alkanes, forms around Ba. In addition, the electronic charges of the surface lattice oxygen are important for H2 desorption. The electronic charge depends on hydrogen coverage: electron-rich surface lattice oxygen, which is favorable for H2 desorption, forms at high hydrogen coverage. Therefore, a part of the surface lattice oxygens of perovskite would be covered with hydrogen atoms under the reaction atmosphere, leading to effective H2 desorption and the proceeding catalytic cycle via the MvK mechanism.

DOI： 10.1021/acs.jpcc.0c00138

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Scopus

Publisher：Rsc Advances  

Catalytic methane steam reforming was conducted at low temperature using a Pd catalyst supported on Ce<inf>1-x</inf>M<inf>x</inf>O<inf>2</inf> (x = 0 or 0.1, M = Ca, Ba, La, Y or Al) oxides with or without an electric field (EF). The effects of the catalyst support on catalytic activity and surface proton hopping were investigated. Results show that Pd/Al-CeO<inf>2</inf> (Pd/Ce<inf>0.9</inf>Al<inf>0.1</inf>O<inf>2</inf>) showed higher activity than Pd/CeO<inf>2</inf> with EF, although their activity was identical without EF. Thermogravimetry revealed a larger amount of H<inf>2</inf>O adsorbed onto Pd/Al-CeO<inf>2</inf> than onto Pd/CeO<inf>2</inf>, so Al doping to CeO<inf>2</inf> contributes to greater H<inf>2</inf>O adsorption. Furthermore, electrochemical conduction measurements of Pd/Al-CeO<inf>2</inf> revealed a larger contribution of surface proton hopping than that for Pd/CeO<inf>2</inf>. This promotes the surface proton conductivity and catalytic activity during EF application.

DOI： 10.1039/d0ra01721c

Open Access

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Scopus

PubMed

Publisher：ACS Omega  

Fe-supported heterogeneous catalysts are used for various reactions, including ammonia synthesis, Fischer-Tropsch synthesis, and exhaust gas cleaning. For the practical use of Fe-supported catalysts, suppression of Fe particle agglomeration is the most important issue to be resolved. As described herein, we found that Al doping in an oxide support suppresses agglomeration of the supported Fe particle. Experimental and computational studies revealed two tradeoff Al doping effects: the Fe particle size decreased and remained without agglomeration by virtue of the anchoring effect of doped Al. Also, some Fe atoms anchored by Al cannot function as an active site because of bonding with oxygen atoms. Using an appropriate amount of Al doping is effective for increasing the number of active Fe sites and catalytic activity. This optimized catalyst showed high practical activity and stability for low-temperature ammonia synthesis in an electric field. The optimized catalyst of 12.5 wt % Fe/Ce0.4Al0.1Zr0.5O2-δ showed the highest ammonia synthesis rate (2.3 mmol g-1 h-1) achieved to date under mild conditions (464 K, 0.9 MPa) in an electric field among the Fe catalysts reported.

DOI： 10.1021/acsomega.0c00170

Open Access

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Scopus

PubMed

Publisher：Chemical Communications  

Low-temperature heterogeneous catalytic reaction in an electric field is anticipated as a novel approach for on-demand and small-scale catalytic processes. This report quantitatively reveals the important role of proton coverage on the catalyst support for catalytic ammonia synthesis in an electric field, which shows an anti-Arrhenius behaviour.

DOI： 10.1039/d0cc00482k

Open Access

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Scopus

PubMed

Publisher：Chemistry Letters  

CO<inf>2</inf> methanation was conducted at low temperatures with an electric field. Results show that 5 wt %Ru/CeO<inf>2</inf> catalyst exhibited high and stable catalytic activity for CO<inf>2</inf> methanation with the electric field. The kinetic investigations and in-situ DRIFTS measurements revealed that Ru/CeO<inf>2</inf> catalyst promoted CO<inf>2</inf> methanation and Ru at the RuCeO<inf>2</inf> interface (low-coordinated Ru sites) contributes to the reverse water gas shift reaction at low temperatures in the electric field.

DOI： 10.1246/cl.190930

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Scopus

Publisher：Journal of Chemical Physics  

Understanding heteroatom doping effects on the interaction between H<inf>2</inf>O and cerium oxide (ceria, CeO<inf>2</inf>) surfaces is crucially important for elucidating heterogeneous catalytic reactions of CeO<inf>2</inf>-based oxides. Surfaces of CeO<inf>2</inf> (111) doped with quadrivalent (Ti, Zr), trivalent (Al, Ga, Sc, Y, La), or divalent (Ca, Sr, Ba) cations are investigated using density functional theory (DFT) calculations modified for onsite Coulomb interactions (DFT + U). Trivalent (except for Al) and divalent cation doping induces the formation of intrinsic oxygen vacancy (O<inf>vac</inf>), which is backfilled easily by H<inf>2</inf>O. Partially OH-terminated surfaces are formed. Furthermore, dissociative adsorption of H<inf>2</inf>O is simulated on the OH terminated surfaces (for trivalent or divalent cation doped models) and pure surfaces (for Al and quadrivalent cation doped surfaces). The ionic radius is crucially important. In fact, H<inf>2</inf>O dissociates spontaneously on the small cations. Although a slight change is induced by doping as for the H<inf>2</inf>O adsorption energy at Ce sites, the H<inf>2</inf>O dissociative adsorption at Ce sites is well-assisted by dopants with a smaller ionic radius. In terms of the amount of promoted Ce sites, the arrangement of dopant sites is also fundamentally important.

DOI： 10.1063/1.5138670

Open Access

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PubMed

Publisher：International Journal of Hydrogen Energy  

For a liquid organic hydride system used for a hydrogen carrier, methylcyclohexane (MCH)–toluene cycle is promising. In this cycle, dehydrogenation of MCH is an endothermic reaction and a key step. We have conducted dehydrogenation of MCH over Pt/anatase-TiO<inf>2</inf> catalyst in an electric field to promote MCH dehydrogenation at a temperature as low as 448 K. The electric field application brought high activity of 37% conversion even at 448 K, exceeding the thermodynamic equilibrium of 12%. This Pt/anatase-TiO<inf>2</inf> catalyst showed only a small amount of methane and carbon by-production and showed high activity for 360 min because of surface protonics.

DOI： 10.1016/j.ijhydene.2019.10.133

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Scopus

Publisher：Journal of Physical Chemistry C  

Dehydrogenation of ethane over perovskite oxide catalysts was investigated using the redox of perovskites and H<inf>2</inf>O as an oxidizing agent. The La<inf>0.8</inf>Ba<inf>0.2</inf>MnO<inf>3-Î&acute;</inf> (LBMO) perovskite showed a high catalytic activity for dehydrogenation of ethane. Periodic dry (without H<inf>2</inf>O)-wet (with H<inf>2</inf>O) operation tests revealed that dehydrogenation of ethane in the presence of H<inf>2</inf>O over LBMO proceeded via the Mars-van Krevelen (MvK) mechanism. Under the wet condition with D<inf>2</inf>O instead of H<inf>2</inf>O, D<inf>2</inf> formation was verified, demonstrating that reactive lattice oxygens in LBMO contributed to the dehydrogenation reaction and that they were regenerated by water. Isotopic transient tests with H<inf>2</inf> ¹⁸O and in situ X-ray absorption fine structure measurements revealed that the reduction and oxidation of Mn in LaMnO<inf>3</inf> and LBMO occurred under the reaction atmosphere and that the partial replacement of the La sites with Ba improved the redox ability of Mn, resulting in its high activity. Furthermore, temperature-programmed reduction under H<inf>2</inf> elucidated that the reduction of Mn³⁺ to Mn²⁺ was promoted by Ba doping. The LBMO perovskite showed the very high activity for dehydrogenation of ethane in the presence of H<inf>2</inf>O via the MvK mechanism by virtue of the high redox properties of Mn.

DOI： 10.1021/acs.jpcc.9b06475

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Scopus

Publisher：Journal of Chemical Physics  

Efficient ammonia synthesis at low temperatures is anticipated for establishing a hydrogen carrier system. We reported earlier that application of an electric field on the Cs/Ru/SrZrO<inf>3</inf> catalyst enhanced catalytic ammonia synthesis activity. It is now clear that N<inf>2</inf> dissociation is activated by hopping protons in the electric field. Efficient ammonia synthesis proceeds by an "associative mechanism" in which N<inf>2</inf> dissociates via an N<inf>2</inf>H intermediate, even at low temperatures. The governing factor of ammonia synthesis activity in an electric field for active metals differed from that in the conventional mechanism. Also, N<inf>2</inf>H formation energy played an important role. The effects of dopants (Al, Y, Ba, and Ca) on this mechanism were investigated using activity tests and density functional theory calculations to gain insights into the support role in the electric field. Ba and Ca addition showed positive effects on N<inf>2</inf>H formation energy, leading to high ammonia synthesis activity. The coexistence of proton-donating and electron-donating abilities is necessary for efficient N<inf>2</inf>H formation at the Ru-support interface.

DOI： 10.1063/1.5111920

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Publisher：Rsc Advances  

A Pd catalyst supported on Ba-substituted LaAlO<inf>3</inf> perovskite (Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-δ</inf>) was investigated for NO reduction at low temperature by propylene, which revealed that Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-δ</inf> has remarkably higher activity than other Pd catalysts at low temperatures (≤573 K) for NO reduction by propylene. To elucidate the surface reaction pathway, transient response tests were conducted using ¹⁸O<inf>2</inf>. Also, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were conducted. Comparison with a Ba-impregnated catalyst (Pd/Ba/LaAlO<inf>3</inf>) demonstrated that Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-δ</inf> shows higher activity for the formation of oxygenated species (C<inf>x</inf>H<inf>y</inf>O<inf>z</inf>) as an intermediate for NO reduction because the surface lattice oxygen has improved mobility via Ba²⁺ substitution in LaAlO<inf>3</inf>. Therefore, Pd/La<inf>0.9</inf>Ba<inf>0.1</inf>AlO<inf>3-δ</inf> have high activity for NO reduction, even at low temperatures in a humid condition.

DOI： 10.1039/c9ra03050f

Open Access

Web of Science

Scopus

PubMed

Publisher：Applied Catalysis A General  

Modified Ga-α-Al<inf>2</inf>O<inf>3</inf> catalyst with Ba showed high catalytic activity, selectivity and low carbon formation on catalytic ethane dehydrogenation to ethylene even in the presence of steam. The resultant Ba-Ga-α-Al<inf>2</inf>O<inf>3</inf> (Ba/Ga molar ratio = 0.10) catalyst showed high ethylene selectivity (98%), high activity, and stability. Temperature-programmed oxidation measurements revealed that Ba addition suppressed coke formation at Ga sites. XRD, XAFS and TEM results showed the existence of highly dispersed β-Ga<inf>2</inf>O<inf>3</inf> on the α-Al<inf>2</inf>O<inf>3</inf> support, irrespective of Ba addition. Observation of hydrogen adsorption using FT-IR spectroscopy revealed a decrease in the surface tetrahedrally coordinated Ga (designated as Ga(T)) sites by Ba modification, indicating that the surface Ga(T) sites are covered with Ba. Density functional theory calculation revealed that coke formation through ethylene decomposition is likely to occur at surface Ga(T) sites, and revealed that the addition of an optimal amount of Ba to Ga-α-Al<inf>2</inf>O<inf>3</inf> inhibits coke formation at the surface Ga(T) sites, leading to high ethylene selectivity.

DOI： 10.1016/j.apcata.2019.05.008

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Scopus

Publisher：Chemical Communications  

Methane activation on diluted metal ensembles is a challenging task in the field of alloy chemistry. This report describes that synergy between an electric field and Pd-Zn alloy allows improved catalytic activities in the steam reforming of methane. Because of surface protonics, Pd-Pd ensembles are no longer needed. Ligand effects facilitate methane conversion.

DOI： 10.1039/c9cc02794g

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PubMed

Publisher：ACS Sustainable Chemistry and Engineering  

The role of the electric field and surface protonics on low temperature catalytic dry reforming of methane was investigated over 1 wt %Ni/10 mol %La-ZrO<inf>2</inf> catalyst, which shows very high catalytic activity even at temperatures as low as 473 K. We investigated kinetic analyses using isotope and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and kinetic analyses revealed synergetic effects between the catalytic reaction and the electric field with less than one-fifth the apparent activation energy at low reaction temperatures. Results of kinetic investigations using isotopes such as CD<inf>4</inf> and ¹⁸O<inf>2</inf>, in situ DRIFTS in the electric field, and density functional theory calculation indicate that methane dry reforming proceeds well by virtue of surface protonics. CH<inf>4</inf> and CO<inf>2</inf> were activated by proton collision at the Ni-La-ZrO<inf>2</inf> interface based on the "inverse" kinetic isotope effect.

DOI： 10.1021/acssuschemeng.8b04727

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Scopus

Publisher：ACS Catalysis  

10wt%Ni-10wt%Mg-La<inf>0.1</inf>Zr<inf>0.9</inf>O<inf>2-x</inf> (LZO) catalyst shows high reforming activity of methane while suppressing methane combustion on tri-reforming of methane at low temperatures of 473 K in an electric field. On the basis of results of light-on and light-off tests for methane oxidation and temperature dependencies for catalytic methane steam reforming activity with or without the electric field, we found that Mg addition to 10wt%Ni-LZO catalyst suppresses methane combustion, while the methane steam reforming proceeds well by virtue of surface protonics in the electric field. Ni²⁺ on 10wt%Ni-10wt%Mg-LZO catalyst was more cationic than that on 10wt%Ni-LZO catalyst, and NiO-MgO solid solution formed on LZO support played an important role in combustion suppression.

DOI： 10.1021/acscatal.8b02476

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Scopus

Publisher：Chemical Physics Letters  

The structure of Pt-Mn/Al<inf>2</inf>O<inf>3</inf> catalyst which shows high performance for dehydrogenation of methylcyclohexane, a prospective hydrogen carrier, was investigated by XAFS and DFT calculations. Mn addition on Pt/Al<inf>2</inf>O<inf>3</inf> brings higher activity, selectivity, and stability for dehydrogenation of MCH than with Pt/Al<inf>2</inf>O<inf>3</inf> alone. Results of XAFS and DFT calculations revealed that MnO<inf>x</inf> selectively covered the unsaturated coordination of Pt. On the unsaturated step facets such as Pt (1 1 0) and Pt (3 1 1), demethylation proceeds easily. Addition of Mn on Pt/Al<inf>2</inf>O<inf>3</inf> catalyst brought selective dehydrogenation of MCH by coverage of such step sites with MnO<inf>x</inf>.

DOI： 10.1016/j.cplett.2018.09.026

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Scopus

Publisher：Chemistry Letters  

Dehydrogenation of methylcyclohexane (MCH) was conducted over Pt/TiO<inf>2</inf>-Al<inf>2</inf>O<inf>3</inf> catalysts, showing high activity, selectivity, stability, and high mechanical strength. XPS measurements revealed that the binding energy of Pt 4d<inf>5</inf>/2 shifted to a lower energy by adding TiO<inf>2</inf> due to electron donation from TiO<inf>2</inf>. Formed toluene released immediately on electron-rich Pt before further decomposition to form methane and coke thanks to π-coordination. This phenomenon improved the catalytic performance, ensuring high selectivity, and durability for methylcyclohexane dehydrogenation.

DOI： 10.1246/cl.170722

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Publisher：Applied Catalysis A General  

Methylcyclohexane (MCH) is a prospective hydrogen carrier candidate. Although Pt/Al<inf>2</inf>O<inf>3</inf> catalyst shows high conversion for dehydrogenation of MCH at 623 K, methane formation and deactivation caused by coke deposition are issues over the catalyst. Results of this study demonstrate that Mn addition to Pt/Al<inf>2</inf>O<inf>3</inf> brought higher selectivity and stability for dehydrogenation of MCH than with Pt/Al<inf>2</inf>O<inf>3</inf> alone. Although Pt and Mn do not form an alloy structure, Pt and Mn form an adjacent structure, and the unsaturated coordination of Pt which promotes methane formation and deactivation decreased. Pt-Mn/Al<inf>2</inf>O<inf>3</inf> shows high catalytic performance by virtue of the coverage of such sites by MnO<inf>x</inf>.

DOI： 10.1016/j.apcata.2017.06.017

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Scopus

Publisher：Applied Catalysis A General  

To elucidate specific functions of supports, we investigated steam reforming of toluene as a model compound of biomass tar over Co catalyst supported on perovskite-type oxide. Co-supported La<inf>0.7</inf>Sr<inf>0.3</inf>AlO<inf>3-δ</inf> catalyst showed the highest activity among various Co-supported catalysts. STEM measurements and XPS measurements revealed the coexistence of La cation and lattice oxygen defect produces an anchoring effect to Co particles. The lattice oxygen release rate on each catalyst was measured with H<inf>2</inf>¹⁸O steady-state isotopic transient kinetic analysis (SSITKA). The anchoring effect, higher dispersion of Co and redox property, are important for the high catalytic performance of Co/La<inf>0.7</inf>Sr<inf>0.3</inf>AlO<inf>3-δ</inf> catalyst on toluene steam reforming.

DOI： 10.1016/j.apcata.2017.03.026

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Scopus

Publisher：Applied Catalysis A General  

Ba addition to supported Ni catalysts was investigated on steam reforming of toluene, as a model compound of biomass tar. Ba addition showed drastic promotive effects on catalytic activity and tolerance against oxidation. Various catalytic tests and characterization were conducted, including pressure dependence, Arrhenius plots, STEM and XAFS observations, dispersion of supported Ni, and temperature programmed reduction. Results revealed that the electron donation from Ba to Ni enabled high catalytic performance of Ba/Ni/LaAlO<inf>3</inf> perovskite catalyst.

DOI： 10.1016/j.apcata.2016.11.026

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Publisher：Catalysis Today  

We investigated steam reforming of toluene as a model compound of aromatic hydrocarbons included in biomass tar over Co supported La<inf>0.7</inf>Sr<inf>0.3</inf>AlO<inf>3-δ</inf> (LSAO), perovskite oxide. Ni-supported LSAO catalyst has shown high activity and coke resistance from the redox property of lattice oxygen in/on the LSAO support. Co is known as an active metal for this reaction, so Co/LSAO catalyst was investigated in this work. Co/LSAO catalyst, which showed high steady-state activity and stability, was characterized using H<inf>2</inf>¹⁸O isotopic transient response tests, STEM, FT-IR, Arrhenius plot and partial pressure dependence to elucidate high and stable catalytic activity. In situ FT-IR measurements revealed that reaction intermediates on Co/LSAO desorbed at 873 K or lower temperatures. Although redox property of lattice oxygen did not change at around 848 K based on isotopic transient tests, the Arrhenius plots indicate that the rate-determining step changed at around 848 K because of reaction intermediate decomposition desorption. Fast reaction and desorption of absorbed intermediates on Co/LSAO enable catalytic stability during toluene steam reforming.

DOI： 10.1016/j.cattod.2015.08.059

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Publisher：Catalysis Letters  

Methylcyclohexane (MCH) is expected as a hydrogen carrier. Dehydrogenation of MCH was conducted over supported Pt catalysts at 623 K. Pt/TiO<inf>2</inf> showed high stability for dehydrogenation and good resistance for coke formation. The partial pressure dependence of MCH, toluene, and H<inf>2</inf> was investigated for Pt/TiO<inf>2</inf> and Pt/Al<inf>2</inf>O<inf>3</inf> catalysts, which showed different tendencies for toluene partial pressure. The reaction order of toluene partial pressure for Pt/TiO<inf>2</inf> was almost zero, but that for Pt/Al<inf>2</inf>O<inf>3</inf> was a negative value. Toluene inhibited the Pt/Al<inf>2</inf>O<inf>3</inf> catalytic activity, but that of Pt/TiO<inf>2</inf> was unaffected. The SMSI effect was confirmed on Pt/TiO<inf>2</inf> by CO chemisorption measurement. Pt on TiO<inf>2</inf> became an electron-rich state compared to Pt⁰ because of the electron donation from TiO<inf>x</inf>, and the toluene adsorption to Pt on TiO<inf>2</inf> was weakened.

DOI： 10.1007/s10562-015-1623-3

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Language：Japanese   Publisher：The Japan Petroleum Institute  

DOI： 10.11523/sekiyu.2016.0_48

CiNii Research

Language：English   Publisher：The Japan Petroleum Institute  

Ni/perovskite-type oxide catalyst (Ni/La_0.7Sr_0.3AlO_2.85: LSAO) shows high catalytic activity and low carbon formation during the steam reforming of aromatic hydrocarbons because of the high mobility of lattice oxygen in the support. The reaction mechanisms of the catalyst were investigated by characterizations and catalytic activity tests for steam reforming of various hydrocarbons including toluene, methylcyclohexane, and <i>n</i>-heptane. The catalytic performance was affected by the reactant structure, as revealed by Arrhenius plots and FT-IR analyses. Adsorption state and stability of reaction intermediates were very important factors in the catalytic activity for steam reforming.

DOI： 10.1627/jpi.58.86

Open Access

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CiNii Research