Yoshihiro Chida

High-entropy alloys (HEAs) have attracted considerable attention to improve performance of various electrocatalyst materials. A comprehensive understanding of the relationship between surface atomic-level structures and catalytic properties is essential to boost the development of novel catalysts. In this study, we propose an experimental study platform that enables the vacuum synthesis of atomic-level-controlled single-crystal high-entropy alloy surfaces and evaluates their catalytic properties

We investigated the enhancement behaviors of oxygen reduction reaction (ORR) properties for Pt/Cr–Mn–Fe–Co–Ni (Cantor alloy)/Pt(111) and (110) lattice stacking surfaces in 0.1 M HClO4 by varying melamine concentrations from 0.01 to 10 μM using a rotating disk electrode method. The ORR activity and structural stability of the Pt surfaces are surely correlated with the melamine concentration. The initial specific activity of Pt/Cantor alloy/Pt(111) depended on the added melamine concentration; act

In this work, we study the oxygen reduction reaction (ORR) properties of Pt-containing 3d transition-metal high-entropy alloy (Pt-HEA) surfaces, focusing on the constituent alloying elements. The surface Pt and underlying Cr-Mn-Co-Ni(111) (Pt/Cr-Mn-Co-Ni(111)) stacked lattice layers, which are synthesized through the vacuum deposition of the underlying alloy and surface Pt stacking layers on Pt(111) substrate, exhibit high pristine ORR activity and structural stability under potential-cycle load

We investigated oxygen reduction reaction (ORR) properties of Pt-containing compositionally complex alloy (Pt-CCA) single-crystal model catalyst surfaces to optimize dry-process synthesis conditions, that is, CCA compositions of less-noble alloying elements and their synthesis (annealing) temperatures. Using a machine-learning approach, we effectively navigated the large space of possible synthesis conditions to minimize the experimental workload. The ORR activity and durability of the Pt/CCA/Pt

We investigated atomically resolved interface microstructures of vacuum-deposited Pt on SnO2(hkl) (hkl = 110, 101, 111; Pt/SnO2(hkl)) substrate surfaces. The Pt/SnO2(hkl) samples were prepared by electron-beam deposition of a 1.6-nm-thick Pt layer on SnO2(hkl) at room temperature under ultrahigh vacuum (∼10−8 Pa) followed by thermal annealing. Cross-sectional structural analysis was conducted by scanning transmission electron microscopy combined with x-ray energy dispersive spectroscopy and x-ra

We synthesized an oxygen reduction reaction (ORR) model catalyst surface of Pt(111)/Nb-doped SnO2(101) (Nb:SnO2) coherent lattice stacking layers on a Pt(111) substrate and investigated the influence of the surface strain of the Pt(111) layer on ORR activity enhancement. The Nb:SnO2 lattice stacking layer was synthesized through arc-plasma deposition (APD) of SnNb on Pt(111) in a vacuum chamber (base pressure <10−7 Pa), followed by thermal annealing at 823 K for 120 min under 1 atm of dry air. T

Introduction Multi-component alloys (MCAs) have been attracted much attention in various engineering application fields. [1] By changing numbers of constituent elements ( n ) as well as their composition ratios (𝑥) of MCAs, the mixing-entropy (ΔS mix = −𝑅∑(𝑖=1→ n ) 𝑥 𝑖 ln 𝑥 𝑖 ) increases with increasing n , resulting in reduced Gibbs free-energy (ΔG = ΔH - TΔS) of the MCAs, which correlates with interesting bulk material’s properties. Furthermore, the MCAs surfaces possess specific chemical prop

Introduction An idea of multi-elemental alloying, mainly high-entropy alloying, has gained attention to boost the performance for various electrocatalysis. [1] Indeed, our previous study for single-crystal surfaces of Pt and underlaid equiatomic Cr-Mn-Fe-Co-Ni (known as Cantor alloy [2]) model catalysts demonstrates that enhanced oxygen reduction reaction (ORR) activity at a pristine state and improved electrochemical structural stability even through the potential cycle (PC)-loading. [3] Furthe

Introduction Nanoparticles of Pt as well as Pt-based alloys are widely used as cathode catalyst materials for proton exchange membrane fuel cells (PEMFC). However, electrochemical stability of the materials is rather low under practical operating conditions of PEMFC cathode, resulting in severe deactivation of oxygen reduction reaction (ORR). Therefore, further material’s developments are required for next-generation PEMFC cathode catalysts, i.e., more enhanced ORR durability with low platinum g