Rationally Designed Co3O4-C Nanowire Arrays on Ni Foam Derived From Metal Organic Framework as Reversible Oxygen Evolution Electrodes with Enhanced Performance for Zn-Air Batteries

The development of high activity and stability nonprecious metal catalysts for oxygen evolution and reduction is necessary to solve energy supply issues. Here, porous nanowire arrays composed of Co3O4 nanoparticles and carbon species are prepared by a facile carbonization of the metal-organic framework materials of ZIF-67 which directly grow on Ni foam. The obtained hybrid materials possess a large surface area of 345 m(2) g(-1) and a high carbon content. The hierarchically interconnected nanowire arrays with porous structure strongly immobilized on Ni foam facilitate the diffusion of generated gas, shorten electrolyte diffusion distance, and enhance charge transport. As the working electrode for oxygen evolution reaction without any extra modification in 1.0 M KOH, it can provide a stable current density of 10 mA cm-(2) at 1.54 V (vs RHE), along with robust durability. Additionally, the Co3O4-C hybrid materials worked as oxygen reduction catalyst exhibit a positive onset potential of 0.91 V, large limiting current density, and excellent stability. When used as the air catalysts for primary Zn-air batteries, the assembled batteries deliver a large peak power density of 118 mW cm-(2) and excellent operation stability. A variety of characterization results and controlled experiments demonstrate that the efficient performance of this hybrid material toward electrocatalytic reactions originates from the unique electrode configuration, intimate distribution of active species, hierarchically porous configuration, high conductivity of Ni foam, and synergistic effect of Co3O4 and carbonaceous materials.