Molybdate intercalated nickel–iron-layered double hydroxide derived Mo-doped nickel–iron phosphide nanoflowers for efficient oxygen evolution reaction

Abstract

The design of a highly efficient electrocatalyst for oxygen evolution reaction (OER) is of great significance to the clean energy conversion system. Herein, novel Mo-doped NiFe phosphide (Mo-NiFe-P) nanoflowers are developed as robust high-activity catalysts for OER via the phosphidation of MoO₄²⁻ intercalated NiFe-layered double hydroxide (NiFe-LDH). The introduction of high valence Mo can significantly promote the catalytic activity of OER because of the strong electronic interactions with Ni and Fe. By tailoring the amount of molybdate intercalated into NiFe-LDH, the optimal phosphide shows outstanding overpotentials of 261 and 272 mV to drive current densities of 50 and 100 mA cm⁻² in 1 mol L⁻¹ KOH. This work demonstrates that the amount of molybdate influences the structure of phosphide prepared by the intercalated LDHs and also affects the electrocatalytic behavior. In addition, density functional theory (DFT) calculations show that introducing Mo could alter the intrinsic electronic structure of NiFe-P, which, in turn, could accelerate the reaction kinetics. This approach could be extended to the preparation of other cost-efficient phosphides for OER.