Ichizo Yagi

The oxygen reduction reaction (ORR) is a key reaction in polymer electrolyte fuel cells and metal–air batteries. In these electrochemical systems, platinum group metals (PGMs) have been widely used as ORR electrocatalysts. Because of material cost and scarcity of platinum group metals, non-PGM electrocatalysts are considered to be an ideal alternative for mass production with low material cost. Many non-PGM electrocatalysts have been intensively studied such as pyrolyzed Fe-, N-doped carbon (Fe–

Perfluorosulfonated ionomer (PFSI), such as Nafion, in polymer electrolyte fuel cells (PEFCs) has been recognized as an important component to shuttle protons during the electrocatalytic reactions, especially the oxygen reduction reaction (ORR) at the cathode. However, a molecular structure of PFSIs inside catalyst layers in PEFCs has been unclear, since the polymers surrounding the gas-diffusion electrode with meso-to-macroporous structures have been considered to be much more complicated to re

A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.

For ligand-protected gold clusters, geometrical differences of gold cores and/or the presence of secondary gold core-ligand interactions influence their unique optical and electronic properties and can, in principle, be detected by spectral changes of gold core vibrations (phonon modes) in ultralow-frequency Raman spectroscopy. We report experimental and theoretical Raman spectra of Au₈ clusters protected by phosphine ligands particularly in the "gold cluster fingerprint" region from

Pt-based nanostructured electrocatalysts supported on carbon black have been widely studied for the oxygen reduction reaction (ORR), which occurs at the cathode in polymer electrolyte fuel cells. Because sluggish ORR kinetics are known to govern the cell performance, there is a need to develop highly active and durable electrocatalysts. The ORR activity of Pt-based electrocatalysts can be improved by controlling their morphology and alloying Pt with transition metals such as Ni. Improving the ca

The electrodeposition of Te on a single-crystalline Au(111) electrode was studied with 1064-nm-excited SH rotational anisotropy measurements. The SH rotational anisotropy was significantly changed with the first underpotential deposition (upd) of Te, and the bulk Te deposition attenuated the anisotropic character of the overall surface symmetry. The change in the SH rotational anisotropy during the first upd of Te was examined using two different models. The first model considered only the contr

Pt-based nanostructures immobilized on carbon supports have been widely used as electrocatalysts. Their catalytic activity can be improved by support modification including nitrogen doping and coating with nitrogen-containing polymers, where nitrogen atoms possibly interact with surface Pt atoms at a catalyst/support interface. To understand electronic effects of nitrogen-doped and polymer-coated carbon supports on the catalytic activity of Pt-based nanostructured catalysts, we prepared Pt3Ni na

We synthesized PtNi alloy nanowires (PtNi NWs) at three different temperatures of 433, 494, and 533 K (NW433 K, NW494 K, and NW533 K, respectively) and then investigated their catalytic activity and durability for the oxygen reduction reaction (ORR) in acidic media. Ni contents in the PtNi NWs increase as the synthesis temperatures increase from below 5 at. % for NW433 K up to about 15 at. % for NW493 K and NW553 K. PtNi nanoparticles (PtNi NPs), which are the unconsumed intermediate during the

The interfacial electronic structure of a CO-covered polycrystalline platinum electrode has been studied by using the optical second harmonic generation (SHG) and sum frequency generation (SFG) techniques with various excitation wavelengths. Although the nonlinear optical (NLO) signal was enhanced by the absorption of CO at all excitation wavelengths employed in this study, the potential dependent behaviors of the NLO signal were different between the near-infrared excitation and the visible exc