Rational Dispersion of Co2P2O7 Fine Particles on N,P-Codoped Reduced Graphene Oxide Aerogels Leading to Enhanced Reversible Oxygen Reduction Ability for Zn-Air Batteries

Developing low-cost and highly efficient non-precious-metal-based bifunctional electrocatalysts for both oxygen reduction and evolution reactions concerns the key steps for the fabrication of rechargeable metal-air batteries. Herein, a rationally designed strategy is developed to join the merits of metal phosphate and carbonaceous materials for the fabrication of novel hybrid electrocatalysts. Through the self-polymerization of organophosphonic acid and cobalt salts on graphene oxide (GO) under a hydrothermal process to form cobalt phosphonate, and subsequently high-temperature pyrolysis, the N,P-codoped three-dimensional (3D) reduced-graphene-oxide-aerogel-supported (rGOA-supported) Co2P2O7 (CoPi) fine particles (CoPi/NPGA) are obtained. The pyrolysis of cobalt phosphonate introduces abundant heteroatom defects and the in situ formed CoPi particles on rGOA, wherein the rGOA permits enhanced electric conductivity and corrosion resistance. Thereby, these two aspects possess different abilities, and together endow the obtained hybrid material with enhanced electrocatalytic performance. In 0.1 M KOH, CoPi/NPGA affords a positive onset and half-wave potentials in catalyzing oxygen reduction, close to that of the Pt/C benchmark, along with impressive durability. In addition, it also exhibits considerable oxygen evolution electrochemical performance, and renders a potential of 1.57 V to achieve a current density of 10 mA cm(-2) in 1.0 M KOH. Impressively, employed as the air cathode of the assembled Zn-air battery, this synthesized bifunctional catalyst enables high open-circuit potential, large powder density, and impressive cycling durability, holding great potential in practical rechargeable batteries.