Nitrogen doped porous carbon-based bifunctional oxygen electrocatalyst with controllable phosphorus content for zinc-air battery

The controllable construction of non-noble metal based bifunctional catalysts with high activities towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of great significance, but remains a challenge. Herein, we reported an effective method to synthesize cobalt-nitrogen doped mesoporous carbon-based bifunctional oxygen electrocatalyst with controllable phosphorus content (Co-N-P_X-MC, X = 0.5, 1.0, 1.5, 2.0). The mesoporous carbon substrate endowed the as-prepared samples with more exposed active surface (236.50 m²·g⁻¹) and the most appropriate doping ratio of phosphorus had been investigated to be 1.5 (Co-N-P_1.5-MC). For ORR, Co-N-P_1.5-MC exhibited excellent catalytic activity with more positive onset potential (1.01 V) and half-wave potential (0.84 V) than the other samples. For OER, Co-N-P_1.5-MC also showed a low overpotential of 415 mV. Combining experimental results and density-functional theory (DFT) calculations, the outstanding bifunctional catalytic performance of Co-N-P_1.5-MC was due to the synergistic cooperation between the P and N dopants, which could reduce the reaction barriers and was favorable for ORR and OER. Moreover, the Zn-air battery using Co-N-P_1.5-MC as the cathode showed remarkable battery performance with high stability (could operate stably for over 160 h at 10 mA·cm⁻²) and maximum power density (119 mW·cm⁻²), demonstrating its potential for practical applications. This work could provide significant enlightenment towards the design and construction of bifunctional oxygen electrocatalyst for next-generation electrochemical devices.