Hokkaido University · Chemical Engineering
Professor Shohei Tada's research lab specializes in the development and mechanistic understanding of heterogeneous catalysts for sustainable energy conversion, particularly focusing on CO2 hydrogenation to methanol and selective CO methanation. The lab investigates the role of metal-oxide interfaces, especially Cu–ZrO₂ and Ni–CeO₂ systems, to identify active sites and optimize catalyst design through advanced characterization techniques such as XAS, TEM, and pulse titration. A key research direction involves tailoring the structure and composition of mixed oxides (e.g., CuxZryOz, ZnxZr1–xO2–x) to enhance catalytic activity and selectivity by stabilizing highly dispersed metal species and oxygen vacancies.
Figures are computed from collected data and may differ slightly.
We examined the formation mechanism of active sites on Cu/ZrO2 specific toward CO2-to-methanol hydrogenation. The active sites on Cu/a-ZrO2 (a-: amorphous) were more suitable for CO2-to-methanol hydrogenation than those on Cu/t-ZrO2 (t-: tetragonal) and Cu/m-ZrO2 (m-: monoclinic). When a-ZrO2 was impregnated with a Cu(NO3)2·3H2O solution and then calcined under air, most of the Cu species entered a-ZrO2, leading to the formation of a Cu–Zr mixed oxide (CuaZr1-aOb). The H2 reduction of the thus-f
As for selective CO methanation over heterogeneous catalysts, numerous investigations of the reaction mechanism and catalyst development are reviewed.
We prepared Cu/a-ZrO2 (a-ZrO2: amorphous ZrO2), Cu/m-ZrO2 (m-ZrO2: monoclinic ZrO2), Cu/a-ZrO2/KIT-6, and Cu/t-ZrO2/KIT-6 (t-ZrO2: tetragonal ZrO2) by a simple impregnation method and examined the effect of the ZrO2 phase on CO2-to-methanol hydrogenation. We discovered a-ZrO2-containing catalysts with high activity and selectivity in CO2-to-methanol hydrogenation. Next, we focused on Cu species formation on the above-described catalysts. While pure CuO was observed on Cu/m-ZrO2 and Cu/t-ZrO2/KIT
We examined active sites for CO2 methanation over Ni/CeO2 catalysts prepared by a wet impregnation method. Four types of Ni/CeO2 with Ni loadings of 1, 3, 5, and 10 wt % were used in this study, assuming that the Ni sites are well dispersed in the catalysts when changing the Ni loading. According to powder X-ray diffraction and scanning transmission electron microscopy, the low-loading catalysts (1 and 3 wt %) consist mainly of Ni–Ce mixed oxides. The results of temperature-programmed reduction
Recently, ZnxZr1–xO2–x catalysts have attracted attention as next-generation CO2-to-methanol hydrogenation catalysts. In this study, we examined the effect of the Zn content on CO2-to-methanol hydrogenation over ZnxZr1–xO2–x catalysts and determined the active-site structure through both calculations and experiments. When the Zn content was low, ZnxZr1–xO2–x contained Zn clusters (isolated [ZnOa] clusters and [ZnbOc] oligomers). The presence of clusters indicates the formation of Zn–O–Zr sites.
Transmission electron microscopy (TEM), CO pulse, and N2O pulse titration were applied to measuring Ni particle sizes on Ni/α-Al2O3 catalysts. It was clarified for the first time that the N2O pulse titration could estimate the size at titration temperature between 50 and 100 °C, which was confirmed by TEM observation. This agreement in the Ni particle sizes by N2O titration and TEM observation means that the Ni surface was fully covered with the monolayer of oxygen formed by N2O decomposition an
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