Synthesis of flower-like cobalt, nickel phosphates grown on the surface of porous high entropy alloy for efficient oxygen evolution

Abstract

The development of cheap, efficient and high activity non-noble-metal oxygen evolution reaction (OER) electrocatalysts is of great interest in promoting the application of water splitting. Herein, the flower-like phosphates were grown in situ on a porous microwave sintered CoCrFeNiMo high entropy alloy (HEA) by the hydrothermal–phosphorization method. The metal phosphates can promote the formation of hydroxides with high catalytic activity on the surface of the catalyst. The obtained porous HEA phosphates exhibit a low overpotential of 220 mV at 10 mA cm−2, a small Tafel slope of 30.3 mV dec−1 and superior stability in 1.0 M KOH. Especially, after continuous cyclic voltammetry (CV) 5000 cycles, the catalyst only requires the overpotential of 210 mV at 10 mA cm−2. The enhanced OER performance of this porous HEA is be attributed to 3D internal connected nanoporous structure, high conductivity, abundant metal (oxy)hydroxide nanosheets and the presence of phosphonates, that provides a sufficiently large surface exposure and allows the acceleration of the electron transfer rate between various species.