Naoto Todoroki

The development of renewable energy technologies is essential to achieve carbon neutrality. Hydrogen can be stably stored and transported in large quantities to maximize power utilization. Detailed understanding of the characteristics and operating methods of water electrolysis technologies, in which naturally intermittent fluctuating power is used directly, is required for green hydrogen production, because fluctuating power-driven water electrolysis processes significantly differ from industri

We evaluated the electrochemical CO2 reduction reaction (ECR) on low-index Au single crystal surfaces (Au(111), (100), and (110); Au(hkl)) and discussed the surface-atomic-arrangement-dependence of Au on the ECR. Online-electrochemical mass spectrometry (OLEMS) results revealed that the onset potential of the quadrupole mass spectrometer (Q-mass) ion signal for the reduction product carbon monoxide (CO; m/z = 28) is ca. 0.3 V lower on the Au(110) surface than on the Au(111) and (100) surfaces. F

Highly active and inexpensive anode materials are required for large-scale hydrogen production using alkaline water electrolysis (AWE). Here, heterolayered nanostructures of Ni-Fe hydroxides/oxides with high activity for the oxygen evolution reaction (OER) were synthesized on a 316 stainless steel (SS) substrate through constant current density electrolysis. The thicknesses, morphologies, and compositions of the nanostructures, generated through dealloying and surface oxidation of the SS element

We investigated electrochemical stability of the NiFe-hydroxide/oxide-catalyst-layer covered stainless-steel(SS)-anode (NiFe-HyOx/SS) for alkaline water electrolysis. The NiFe-HyOx catalyst layer was synthesized through constant current density electrolysis of 30 mA/cm2 in 1 M KOH solution of a 316 SS plate at 75 ℃ for 5 h. The initial overpotential of oxygen evolution reaction (OER) was estimated to be ca. 270 mV at 100 mA/cm2 and the potential kept almost constant during applying the 20,000 po

A novel nanoparticle-stacking thin film (NPSTF) of Pt–Ni alloy for highly active oxygen reduction reaction (ORR) electrocatalyst was synthesized. The Pt mass activity of the synthesized Pt–Ni NPSTF were 10-fold higher than commercial carbon-supported Pt catalysts. The remarkable ORR activity enhancement of the Pt–Ni NPSTF was attributed to the modified electronic properties of the surface Pt-enriched layers induced by underlying Ni atoms and to the increased active surface area achieved by stack

Alkaline water electrolysis (AWE) is a large-scale hydrogen production technology. A major degradation mode of AWE when using fluctuating power derived from renewable energies is the detachment of the catalyst layer (CL). Here, this study investigates the CL detachment mechanism of NiCo₂O₄-CL-coated Ni (NCO/Ni) electrodes under an accelerated durability test (ADT) simulating a fluctuating power and the effect of post-annealing on detachment behavior. Microstructural analysi

We investigated the atomic-scale structure and electrochemical stability of a Pt-enriched topmost surface (Pt-enriched Ni/Pt(111)) prepared through monolayer Ni deposition on Pt(111) at 823 K using molecular beam epitaxy. Reflection high-energy electron diffraction patterns and an ultra-high vacuum scanning tunneling microscopic (UHV-STM) image of the Pt-enriched Ni/Pt(111) surface showed that the surface has long-range-ordered six-fold symmetry with atomic-scale corrugations. Although the oxyge

The introduction of a SnO2(110) interlayer remarkably enhances the oxygen evolution reaction (OER) activity and electrochemical stability of RuO2/Nb-doped TiO2(110) single-crystal oxide heterostructure. The SnO2 interlayer reduces the OER overpotential of RuO2/Nb:TiO2(110) by 25 and 55 mV before and after a chronopotentiometry (CP) measurement of 0.5 mA cm–2 for 2 h, respectively. The addition of the SnO2 interlayer significantly reduces the interfacial resistance between RuO2 and TiO2 in the as

We investigated the dissolution behaviors of major constituent elements (Fe, Cr, Mn, and Ni) and minor elements (Mo, Ti, and Nb) from austenitic stainless steel (SS) oxygen evolution electrodes for alkaline water electrolyzers (AWE) under potential cycle (PC) loadings. SS substrates of 301, 304, 310S, 316, 321, and 347 grades were used as the starting electrodes. Considering the potential fluctuation environments of AWE, PCs between 0.5 and 1.8 V vs. reversible hydrogen electrode were loaded for

Effects of surface Pt monolayer thickness on electrochemical oxygen reduction reaction of molecular-beam-epitaxially-prepared Pt/Ni/Pt(111) were investigated. The effective thickness of Pt for stabilizing the topmost surface can be deduced to be three monolayers.

Interlayer and surface Ir-modified Pt/Pd(111) model catalyst surfaces [Pt/Ir/Pd(111) and Ir/Pt/Pd(111)] were synthesized as surface structural models for third element-modified core–shell-type Pd@Pt catalysts by vacuum depositions of Ir and Pt on the Pd(111) substrate surface. The oxygen reduction reaction (ORR) properties (initial activity and electrochemical stabilities) were compared to non-Ir-modified Pt/Pd(111) and discussed on the basis of atomic structural observations of the near surface

Oxygen reduction reaction (ORR) properties are investigated for the Pt/Zr/Pt(111) surfaces prepared through arc-plasma depositions of Zr and Pt on a Pt(111) substrate. The synthesized Pt(111)-shell surfaces on Pt–Zr(111) alloy layers exhibited 3- to 5-fold higher ORR activities than the clean Pt(111): the ligand effect induced by charge transfers between Pt and Zr was considered to be the dominant activity enhancement factor, because tensile strains in the Pt-shell were relieved by the stacking