CoP nanoparticles embedded in three-dimensional porous network-like structured N, O co-doped carbon nanofibers as an effective bi-functional electrocatalyst for rechargeable zinc–air batteries†

Abstract

The development of noble metal-free bi-functional electrocatalysts is consistent with the current concept of sustainable development of energy systems. In this study, we develop a strategy to prepare ZIF-67-derived CoP nanoparticles embedded in three-dimensional porous network-like structured N, O co-doped carbon nanofibers (CoP@N, O co-doped PCNFs) through the processes of electro-blown spinning, carbonization, and in situ phosphorization. And they are regarded as an ORR/OER bi-functional electrocatalyst, which is applied in rechargeable zinc–air batteries. The hierarchically porous structure of the carbon nanofibers facilitates the diffusion of dissolved oxygen and the formation of abundant gas–liquid–solid interfaces in the liquid electrolyte, leading to enhanced ORR/OER activity. Therefore, the ORR half-wave potential of the CoP@N, O co-doped PCNFs reached 0.81 V. In particular, the OER overpotential exhibited 250 mV at 10 mA cm⁻². More importantly, the zinc–air battery constructed with the CoP@N, O co-doped PCNF catalyst has a high specific capacity (797.2 mA h g⁻¹) and energy density (927.9 W h kg⁻¹) at a current density of 10 mA cm⁻² and can stably cycle for 500 h at a current density of 2 mA cm⁻². The findings will provide a new paradigm for designing more practical noble metal-free bi-functional electrocatalysts for rechargeable zinc–air batteries.