Defect engineering on three-dimensionally ordered macroporous phosphorus doped Co3O4–δ microspheres as an efficient bifunctional electrocatalyst for Zn-air batteries

Abstract Developing low-cost and high-efficiency bifunctional electrocatalysts for both oxygen evolution and reduction reactions is urgent to fulfill the practical application of rechargeable Zn-air batteries (ZABs). However, to explore the high catalytic performance of air electrocatalysts still remains a challenge. In response, a three-dimensionally ordered macroporous (3DOM) Co3O4 electrocatalyst is designed and synthesized through a nanocasting strategy. A well-controlled phosphorization treatment is further conducted to induce defect engineering on the resulting P-doped Co3O4–δ (3DOM P-Co3O4–δ). With the oxygen vacancy (Vo) tailoring, partial reduction from Co3+ to Co2+ is verified as the key to improving the intrinsic electrocatalytic bifunctionality. By incorporating the geometric and electronic merits, 3DOM P-Co3O4–δ possesses an ORR half-wave potential of 0.82 V and an OER overpotential of 366 mV to achieve 10 mA cm–2, which is comparable to noble-metal benchmarks. Particularly, under galvanostatic cycling measurements, ZABs using 3DOM P-Co3O4–δ containing air cathode showcase a potential gap of 0.84 V with negligible voltage fading over 250 h at 10 mA cm–2.