One-step formation of ZrON thin film on surface of carbon fine particles for membrane electrode assembly

Abstract

Zirconium nitride and oxynitride films were deposited on alumina or carbon particles by reactive sputtering using a magnetron sputtering apparatus with a Zr hollow cylindrical target and a vibrating equipment with heating capability. The vibrating equipment developed in this study was effective if the particles are spherical and highly monodisperse. Uniform film deposition was achieved over the entire surface of highly monodisperse spherical alumina particles using the vibrating equipment during deposition. Pure ZrN crystalline layers was deposited under Ar and N2 gas flows with heating on XC-72 carbon powder particles removed adsorbed oxygen. Energy dispersive x-ray spectroscopy mapping analysis for deposited XC-72 carbon particles showed ubiquitous film deposition on agglomerated particles regardless of vibration during sputtering. Uniform film deposition with vibrating equipment was achieved on the entire surface of CGB-10 particles with more spherical and monodisperse than XC-72 but precipitated crystalline phase depended on unintentional oxygen chemisorbed on the particles. Addition and increase in flow rate of oxygen to the sputtering gas resulted in the formation of desired crystalline phase, Zr2ON2, Zr7O8N4, and monoclinic ZrO2, precipitated in the film using CGB-10 particles with chemisorbed oxygen removed. Current density for oxygen reduction reaction measured for MEA made from CGB-10 particles with ZrON-based crystals deposited was larger than that for thin film deposited on a carbon plate substrate.