Shunsuke Yagi

The oxygen evolution reaction that occurs during water oxidation is of considerable importance as an essential energy conversion reaction for rechargeable metal-air batteries and direct solar water splitting. Cost-efficient ABO3 perovskites have been studied extensively because of their high activity for the oxygen evolution reaction; however, they lack stability, and an effective solution to this problem has not yet been demonstrated. Here we report that the Fe(4+)-based quadruple perovskite Ca

Ever-proposed descriptors of catalytic activity for the oxygen evolution reaction (OER) were systematically investigated. A wide variety of stoichiometric perovskite oxides ABO3 (A = Ca, Sr, Y, La; B = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) were examined as OER catalysts. The simplest descriptor, eg, electron number of transition-metal ions at the B-site, was not applicable for OER overpotentials (η) of the compounds tested in this study. Another descriptor, oxygen 2p band center relative to Fermi energ

The electrochemical stabilities of several electrodes were investigated by cyclic voltammetry and chronoamperometry in a tetrahydrofuran solution containing phenylmagnesium chloride and aluminum chloride. The existence of chloride ions in the electrolyte caused pitting of affordable, non-noble metal electrodes at high potentials and crucially lowered their corrosion resistance. In contrast, Pt and glassy carbon electrodes exhibited high corrosion resistance. Since Pt is expensive and bulk glassy

Transition metal oxides have been extensively investigated as novel catalysts for oxygen evolution reaction (OER). Partial elemental substitutions are effective ways to increase catalytic performance and such electronic interactions between multiple elements are known as synergistic effects. However, serious issues such as random atomic arrangement and ambiguous roles of constituent elements humper theoretical investigations for rational materials design. Herein, we describe systematic study on

Bimetallic sulfides have been attracting considerable attention because of their high catalytic activities for oxygen reduction reaction (ORR) and oxygen evolution reaction; thus, they are considered efficient catalysts for important energy conversion devices such as fuel cells and metal-air batteries. Here, the catalytic activity of a novel catalyst composed of Co_9-<i>x</i>Ni_<i>x</i>S₈ nanoparticles immobilized on N-doped carbons (Co_9-<i>x</i>Ni<sub><

A wide variety of ions and molecules can be accommodated in the framework structure of Prussian blue (PB) and its analogs (PBAs). Mono- and polyvalent ions accommodated in the PB framework structure and PBAs can be extracted or re-inserted by redox reactions of transition metal ions composing the framework for charge compensation. In the present work, we report the detailed mechanism of the electrochemical inseration/extraction of Mg2 + ions and the effect of anions on the redox chemistry of a P

Synthesis of binary magnesium–transition metal oxides, MgM 2 O 4 (M: Cr, Mn, Fe, Co) and MgNiO 2 , was performed by calcination at relatively low temperatures of 500 and 750 °C for 24 h through inverse coprecipitation of carbonate hydroxide precursors. The important roles of the precipitation agent, sodium carbonate, were clarified by considering equilibria in an aqueous solution. The structure parameters of the obtained binary magnesium–transition metal oxide powders, specifically the occupancy

nanoparticles approximately in diameter were electrochemically formed by liquid-phase reduction (i.e., electroless deposition) using hydrazine as a reducing agent and dispersing barely soluble particles in aqueous solution at . The addition of gelatin into the reaction suspension prevented the coagulation of nanoparticles and also sufficiently suppressed particle growth. Direct reduction of particles did not occur due to the adhesion of gelatin on the surface of particles, and nanoparticles were

Prussian blue (PB) and its analogues (PBAs) have been intensively studied and are now increasingly attractive for battery applications in particular because of their ability to accommodate a wide variety of ions including polyvalent cations. The redox reactions of PB and PBAs are believed to be very fast and reversible. However, it is not always true. In this paper, we clarify the detailed redox behavior of PB in an electrolyte for Li (ion) batteries using an electrochemical quartz crystal micro