Hollow-sphere Co-NC synthesis by incorporation of ultrasonic spray pyrolysis and pseudomorphic replication and its enhanced activity toward oxygen reduction reaction

Abstract

Metal–nitrogen–carbon (M-NC) catalysts have been reported as promising electrocatalysts to replace noble-metal catalysts (Pt/C, Au/C, Ru/C etc.) in many industrial processes. In this regard, carbonized zeolite imidazole frameworks (ZIFs), as precursors of M-NC catalysts, have been extensively studied because of their porosity and ligand composition containing nitrogen and carbon. In this study, we synthesize Co-doped ZnO@ZIF-8 particles from a Co-doped ZnO sphere via the spray pyrolysis method and pseudomorphic replication. Ultrasonic spray pyrolysis is an attractive approach to operate mass production with high-purity homogeneous structures. Further, pseudomorphic replication makes it possible to control the morphology of the metal–organic framework (MOF) particles and easily prepare MOF composite particles. In the study, the pyrolyzed ZIF particles are applied to oxygen reduction reactions in alkaline media, and our results indicate that particles show a high half-wave potential of 0.904 V, which makes them suitable for diverse electrochemical applications.