Petaloid CoP/FeP Composites: Efficiently bifunctional cathode electrochemical oxygen catalysts for aqueous and Solid-State Zinc-Air batteries

[Display omitted] •The petaloid CoP/FeP@PCN catalyst was synthesized with ZIF and melamine as templates.•CoP/FeP@PCN composite serves as a good bifunctional electrochemical oxygen catalyst.•The E1/2 of ORR is 0.894 V and the potential gap between ORR and OER is 0.566 V.•CoP/FeP@PCN-based aqueous ZAB exhibits good performance and 579 h cycling stability.•CoP/FeP@PCN-based solid-state ZAB exhibits 100 h charge–discharge cycling stability. Exploring alternative energy sources and innovative energy storage and conversion technologies is essential for pursuing sustainable development in this global society. Metal-air batteries are considered as one of the most promising green energy sources due to their high energy density and environmentally benign, and the development of efficient cathodic catalysts for metal-air batteries is a critical topic in the energy field. In this work, a two-step high-temperature pyrolysis strategy is proposed to prepare to synthesize the petaloid CoP/FeP@PCN catalyst with tiny Co-ZIF and Fe-ZIF as templates, melamine/thiourea as the carbon framework sources, and (NH4)H2PO4 as the P-sources. Plentiful nanoparticles are homogeneously dispersed on the surface of the petaloid carbon layers. From the configuration perspective, this petaloid structure benefits the adsorption/desorption of the reactants/products and the mass transfer. The optimized CoP/FeP@PCN catalyst serves as a highly efficient bifunctional electrochemical oxygen catalyst, delivering excellent ORR and OER performance with the ORR half-wave potential of 0.894 V (0.1 M KOH) and the OER overpotential of 230 mV (1 M KOH), which is higher than the corresponding monometallic catalysts and most of the reported works. Moreover, the catalytic active site is investigated by DFT calculations. The CoP/FeP@PCN-based aqueous ZAB exhibits exceptional battery performance with high peak power density (175.4 mW·cm−2), large specific capacity (780 mAh·g−1@10 mA·cm−2), and long-term charge–discharge stability. The corresponding solid-state Zn-air battery also performs well with high specific capacity (750 mAh·g−1@5 mA·cm−2) and long-term charge–discharge stability. Both the liquid and solid-state ZABs perform better than the commercial Pt/C+RuO2-based ZAB.