Defect engineering associated with cationic vacancies for promoting electrocatalytic water splitting in iron-doped NiP nanosheet arrays.

Transition metal phosphides are highly efficient catalysts that do not rely on noble metals, which have shown great potential in replacing noble metal catalysts and contributing to the advancement of the electrocatalytic hydrogen production industry. To further enhance the catalytic performance of transition metal phosphides, researchers have discovered that cationic vacancy defects can be utilized to regulate their electronic structure, thereby improving their catalytic properties. In this research, we present the successful synthesis of a bifunctional NiP electrocatalyst (V-NiP) with cationic vacancy defects through electrodeposition and acid etching techniques. The introduction of cationic vacancies after acid etching is confirmed by electron paramagnetic resonance (EPR) spectroscopy. The V-NiP electrocatalyst demonstrates excellent catalytic performance in alkaline environments, achieving a current density of 10 mA∙cm at an overpotential of 52 mV for the hydrogen evolution reaction (HER), and the same current density with an overpotential of 154 mV for the oxygen evolution reaction (OER). Additionally, the V-NiP/NF electrode exhibits remarkable stability over 1000 cyclic voltammetric cycles for both HER and OER. This study presents a novel approach for the synthesis and performance control of highly-efficient transition metal phosphide electrocatalysts, which holds significant importance in the development and design of new energy materials.