Hiroyuki Asakura

To gain insights into single‐atom active sites of iron, nitrogen‐doped carbon (Fe‐N‐C), we performed comprehensive element‐specific spectroscopies including Fe K ‐edge X‐ray absorption, ⁵⁷ Fe Mössbauer, and Fe Kβ _1,3 and valence‐to‐core (VtC) X‐ray emission spectroscopy for two Fe‐N‐C electrocatalysts that exclusively have atomically dispersed FeN ₄ active sites for the oxygen reduction reaction. Experimental VtC X‐ray emission spectra (VtC‐XES) coupled with spectral simulation of FeN ₄ active site models allowed us to determine the dominant active site in each catalyst: FeN ₄ active sites with 14‐membered or 16‐membered rings. Our study will open up possibilities to understand more details on active site structure–activity relationships not only for Fe‐N‐C electrocatalysts but also the other single‐atom (electro)catalysts.

Layered hydrogen silicane (L-HSi) was investigated as a visible-light-responsive hydrogen carrier. Hydrogen evolution was observed under visible-light irradiation, reaching release ratios of 8% in argon and 15% in air after 7 d. Spectroscopic analyses (UV–vis, XPS, ESR) and XRD measurements revealed atmosphere-dependent structural changes. In argon, hydrogen release generates Si dangling bonds, whereas in air the dangling bonds are terminated by oxygen-containing species. These findings clarify the hydrogen release mechanism of L-HSi.

RhO _x /TiO ₂ –Pt photocatalyst demonstrated effective activity for the dehydrogenation of a range of alcohols under visible light irradiation.

Pd oxide, which is epitaxially bonded to the ab surface of Sr₃Ti₂O₇, exhibits cyclic structural fluctuations and excellent catalytic activity for automotive exhaust gas purification.

The epitaxial growth of heterogeneous catalysts needs highly crystalline metal oxide-based ceramics as a catalyst support. However, the inherently low surface area of these ceramic materials poses a significant limitation to their catalytic application. Against this background, this study reveals that loading a very small amount of Pd species onto Sr3Ti2O7, which is a ceramic material synthesized by calcination at 1273 K, leads to the epitaxial bonding of Pd oxide based on the space group of Fm3m to the ab surface of Sr3Ti2O7. Interestingly, the Pd oxide particle with particle sizes in the range of 2–5 nm has a superperiodic structure, where ordered and disordered Pd atoms are cyclically repeated in the a-axial direction of Sr3Ti2O7. Density functional theory calculations suggest that the charge transfer from Sr3Ti2O7 to Pd oxide facilitates the formation of an epitaxial junction and causes structural fluctuations in Pd oxide. The Pd/Sr3Ti2O7 catalyst with a unique heterojunction exhibits excellent catalytic activity for the purification of automotive exhaust gases. In addition, the Pd/Sr3Ti2O7 catalyst is more active than the benchmark Pd/Al2O3 catalyst despite its low surface area of only 2 m2 g-1. This study demonstrates that metal oxide-based ceramics can be used as catalyst materials by precisely designing their heterojunctions.

Carbon-neutral hydrogen production is of key importance for the chemical industry of the future. We demonstrate a new thermal catalytic route for the partial reforming of ethanol into hydrogen and acetic acid with near-zero carbon dioxide emissions. This reaction is enabled by a catalyst containing a high density of atomic Pt ₁ and Ir ₁ species supported on a reactive alpha-molybdenum carbide substrate, achieving a hydrogen production rate of 331.3 millimoles of hydrogen per gram catalyst per hour and an acetic acid selectivity of 84.5% at 270°C, and is therefore more energy-efficient compared with standard reforming. Techno-economic analysis of partial ethanol reforming demonstrates the potential profitability for operation at an industrial scale, presenting the opportunity to produce hydrogen and acetic acid with a substantially reduced carbon dioxide footprint.

Selective catalytic oxidation (SCO) of NH₃ to N₂ is one of the most effective methods used to eliminate NH₃ emissions. However, achieving high conversion over a wide operating temperature range while avoiding over-oxidation to NO_x remains a significant challenge. Here, we report a bi-metallic surficial catalyst (Pt_SCuO/Al₂O₃) with improved Pt atom efficiency that overcomes the limitations of current catalysts. It achieves full NH₃ conversion at 250 °C with a weight hourly space velocity of 600 ml NH₃·h⁻¹·g⁻¹, which is 50 °C lower than commercial Pt/Al₂O₃, and maintains high N₂ selectivity through a wide temperature window. Operando XAFS studies reveal that the surface Pt atoms in Pt_SCuO/Al₂O₃ enhance the redox properties of the Cu species, thus accelerating the Cu²⁺ reduction rate and improving the rate of the NH₃-SCO reaction. Moreover, a synergistic effect between Pt and Cu sites in Pt_SCuO/Al₂O₃ contributes to the high selectivity by facilitating internal selective catalytic reduction.

Single‐atom catalysts have garnered significant attention due to their exceptional atom utilization and unique properties. However, the practical application of these catalysts is often impeded by challenges such as sintering‐induced instability and poisoning of isolated atoms due to strong gas adsorption. In this study, we employed the mechanochemical method to insert single Cu atoms into the subsurface of Fe₂O₃ support. By manipulating the location of single atoms at the surface or subsurface, catalysts with distinct adsorption properties and reaction mechanisms can be achieved. It was observed that the subsurface Cu single atoms in Fe₂O₃ remained isolated under both oxidation and reduction environments, whereas surface Cu single atoms on Fe₂O₃ experienced sintering under reduction conditions. The unique properties of these subsurface single‐atom catalysts call for innovations and new understandings in catalyst design.

Single‐atom catalysts have garnered significant attention due to their exceptional atom utilization and unique properties. However, the practical application of these catalysts is often impeded by challenges such as sintering‐induced instability and poisoning of isolated atoms due to strong gas adsorption. In this study, we employed the mechanochemical method to insert single Cu atoms into the subsurface of Fe₂O₃ support. By manipulating the location of single atoms at the surface or subsurface, catalysts with distinct adsorption properties and reaction mechanisms can be achieved. It was observed that the subsurface Cu single atoms in Fe₂O₃ remained isolated under both oxidation and reduction environments, whereas surface Cu single atoms on Fe₂O₃ experienced sintering under reduction conditions. The unique properties of these subsurface single‐atom catalysts call for innovations and new understandings in catalyst design.