The cobalt carbide/bimetallic CoFe phosphide dispersed on carbon nanospheres as advanced bifunctional electrocatalysts for the ORR, OER, and rechargeable Zn-air batteries.

It is very important, but also challenging to produce high-activity, high durability and affordable non-noble-metal-bifunctional-electrocatalysts for sustainable energy application. Here, one-pot synthesized iron covalent porphyrin polymers (FePor-CPP), with carefully placed Fe, N atoms, a regular porous structure, Co3[Co(CN)6]2 and NaH2PO2 precursors were carbonized into N,P-doped carbon nanospheres with the active species of both bimetallic CoFe phosphides and CoCx nanoparticles (denoted as CoCx/(Co0.55Fe1.945)2P@C). By employing the CoCx/(Co0.55Fe1.945)2P@C as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrode catalysts, superior catalytic activity is achieved with E1/2 of 0.84 V for ORR, and overpotential of 0.39 V at 10 mA cm-2 for OER in an alkaline medium, respectively. Furthermore, CoCx/(Co0.55Fe1.945)2P@C as air electrode for rechargeable Zn-air battery shows power density as high as 131 mW cm-2 and charge-discharge cycle stability, and this suggests the potential application of CoCx/(Co0.55Fe1.945)2P@C in energy transformation systems. The high electrocatalytic performances are revealed to originate from the change of electronic structure of bimetallic (Co0.55Fe1.945)2P via introducing P into the Co0.55Fe1.945 alloy, resulting in a decreased energy gap of CoCx/(Co0.55Fe1.945)2P@C relative to that of CoCx/Co0.55Fe1.945@C. This work proposes a versatile strategy to develop multifunctional non-precious catalysts for this kind of energy-related electrocatalytic reactions.