Harumi Yokokawa

Bio: Harumi Yokokawa is an academic researcher from University of Tokyo. The author has contributed to research in topics: Oxide & Solid oxide fuel cell. The author has an hindex of 58, co-authored 414 publications receiving 12001 citations. Previous affiliations of Harumi Yokokawa include Tohoku University & National Chemical Laboratory.

Characteristics of Slurry‐Coated Nickel Zirconia Cermet Anodes for Solid Oxide Fuel Cells

Abstract: Polarization characteristics were studied in nickel and yttria stabilized zirconia cermet (Ni-YSZ cermet) electrodes in order to search for an adequate fabrication condition of a planar solid oxide fuel cell. Several electrodes were prepared by the slurry coating method, and dc and ac polarization behaviors were investigated at 1273 K in H 2 -H 2 O atmosphere. An experimental equation was derived to describe a typical dc polarization curve of a Ni-YSZ cermet electrode. Effects of fabrication temperature, nickel content, and material powder were investigated in terms of deviation from this equation. Anodic overvoltage with a carefully prepared electrode was decreased to about 0.12 V at 1 A/cm 2

Materials for fuel-cell technologies

Abstract: Fuel cells convert chemical energy directly into electrical energy with high efficiency and low emission of pollutants. However, before fuel-cell technology can gain a significant share of the electrical power market, important issues have to be addressed. These issues include optimal choice of fuel, and the development of alternative materials in the fuel-cell stack. Present fuel-cell prototypes often use materials selected more than 25 years ago. Commercialization aspects, including cost and durability, have revealed inadequacies in some of these materials. Here we summarize recent progress in the search and development of innovative alternative materials.

Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions

Abstract: A fundamental change has been achieved in understanding surface electrochemistry due to the profound knowledge of the nature of electrocatalytic processes accumulated over the past several decades and to the recent technological advances in spectroscopy and high resolution imaging. Nowadays one can preferably design electrocatalysts based on the deep theoretical knowledge of electronic structures, via computer-guided engineering of the surface and (electro)chemical properties of materials, followed by the synthesis of practical materials with high performance for specific reactions. This review provides insights into both theoretical and experimental electrochemistry toward a better understanding of a series of key clean energy conversion reactions including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The emphasis of this review is on the origin of the electrocatalytic activity of nanostructured catalysts toward the aforementioned reactions by correlating the apparent electrode performance with their intrinsic electrochemical properties. Also, a rational design of electrocatalysts is proposed starting from the most fundamental aspects of the electronic structure engineering to a more practical level of nanotechnological fabrication.

Ceramic Fuel Cells

Abstract: A ceramic fuel cell in an all solid-state energy conversion device that produces electricity by electrochemically combining fuel and oxidant gases across an ionic conducting oxide. Current ceramic fuel cells use an oxygen-ion conductor or a proton conductor as the electrolyte and operate at high temperatures (>600°C). Ceramic fuel cells, commonly referred to as solid-oxide fuel cells (SOFCs), are presently under development for a variety of power generation applications. This paper reviews the science and technology of ceramic fuel cells and discusses the critical issues posed by the development of this type of fuel cell. The emphasis is given to the discussion of component materials (especially, ZrO2 electrolyte, nickel/ZrO2 cermet anode, LaMnO3 cathode, and LaCrO3 interconnect), gas reactions at the electrodes, stack designs, and processing techniques used in the fabrication of required ceramic structures.