Enhanced oxygen evolution reaction of metallic nickel phosphide nanosheets by surface modification

Abstract

Employing water splitting as a practicable technique for alternative clean energy requires the development of efficient oxygen evolution electrocatalysts based on inexpensive and earth-abundant materials. Transition metal phosphides have been regarded as promising candidates due to their high electrochemical activity, high conductivity and widespread abundance. However, currently, the oxygen evolution capability of the transition metal phosphides is still limited. It can be noted that the surface state of the electrocatalysts also plays a crucial role in determining the electrocatalytic reaction. In this study, we demonstrate a surface modification strategy using oxygen incorporation in the metallic Ni₂P nanosheets catalyst for the first time, leading to dramatically enhanced oxygen evolution activity. The oxygen-incorporated Ni₂P nanosheets were achieved through a simple low-temperature phosphidation from the Ni(OH)₂ nanosheets precursor. We found that the oxygen incorporation in the Ni₂P nanosheets could actively promote the electrochemical performance and presented stable current density of 10 mA cm⁻² at a small overpotential of 347 mV with a Tafel slope as low as 63 mV dec⁻¹. Furthermore, the large electrocatalytic current is about 25 times enhanced compared with the pure Ni₂P counterpart. Moreover, the high OER performance is superior to most of the reported pure metal phosphide electrocatalysts. These findings point to new opportunities for surface modification to manipulate and improve the reaction of electrocatalysts for designing high performance electrocatalysts and for the investigation of the underlying mechanism of the electrochemical reaction.