Oxygen vacancy-rich ultrafine CoP/Co3O4 nanoparticles as high-efficiency trifunctional electrocatalyst

Exploring highly stable and active electrocatalyst for hydrogen evolution, oxygen evolution and oxygen reduction reactions is an unremitting target for the supply and storage of sustainable energies. Here, we report a type of oxygen vacancy-rich nanostructure in which uniform CoP/Co3O4 nanoparticles (NPs) are coated and dispersed on an amorphous carbon network (pPVP). This hybrid nanostructure labeled as 'CoP/Co3O4-fC-pPVP' is synthesized by a pyrolysis-oxidation-phosphatization strategy, which can accelerate charge transfer and improve carrier separation owing to introducing copious oxygen vacancy. Benefiting from the modulated electronic structure and advantage of interfacial and synergistic effect among active CoP, Co3O4 and pPVP layer, the CoP/Co3O4-fC-pPVP hybrid structure exhibits excellent trifunctional electrocatalytic performance. The scattering wave vector (q) of the samples before and after catalytic reactions remains unchanged from small angle X-ray scattering (SAXS) tests, indicating the stable phase structure. As for CoP/Co3O4-fC-pPVP, only a very low potential of 1.585 V is needed to reach 10 mA cm−2 in the overall water splitting process. Furthermore, the peak power density of CoP/Co3O4-fC-pPVP-based Zn-air batteries reaches 154 mW cm−2 and the charge-discharge voltage gap almost maintains the initial overpotential after 727 h cycle test.