One-step synthesis of carbon-encapsulated nickel phosphide nanoparticles with efficient bifunctional catalysis on oxygen evolution and reduction

As a promising and cost-efficient alternative to noble metal catalysts, transition metal phosphides (TMPs) show highly catalytic performance toward oxygen reduction and evolution reactions (ORR and OER). Mesoporous carbon-coated nickel phosphide (NiP) nanoparticles were successfully synthesized by thermal decomposition at 500 °C under N2/H2 (95:5) atmosphere. The NiP/C hybrid exhibits excellent OER/ORR activity. It can generate an OER current density of 10 mA cm−2 at the overpotential of 0.26 V with a low Tafel slope of 43 mV dec−1, and produce a limited ORR current density of 5.10 mA cm−2 at 1600 rpm with a half-wave potential of 0.82 V via a 4-electron pathway. In addition, the OER/ORR catalytic currents remain considerable stable without significant loss for more than 25 h polarization. This work will open up a new avenue to design a bifunctional catalyst with a superior OER/ORR activity and stability, and this cost-efficient strategy will pave the way for the industrial application of the renewable energy technologies.