Modulation of the morphology and electronic structure of Ni3S2 nano-forests via P and Mo co-doping in polyoxometalates to promote the urea oxidation reaction

Abstract

Heazlewoodite nickel sulfide (Ni₃S₂) is a promising catalyst for the urea oxidation reaction (UOR) due to its facile fabrication and low cost. However, the low active sites inhibit the UOR activity of pure Ni₃S₂. Doping is an effective strategy to modify the active site of an electrocatalyst. Herein, a theory-guided strategy is used for screening the doping elements, and the results indicate that P and Mo co-doping contributes most to enhancing the UOR activity of Ni₃S₂. Then, P and Mo co-doped Ni₃S₂ (P–Mo–Ni₃S₂@NF) is synthesized using polyoxometalate PMo₁₂O₄₀·xH₂O as the precursor. Experimental/theoretical results demonstrate that P and Mo co-doping can regulate the morphology and electronic structure, accelerate electron transfer, increase the Ni³⁺ active sites of Ni₃S₂, improve the conductivity, and strengthen the urea adsorption and *COO desorption. Consequently, the P–Mo–Ni₃S₂@NF electrode shows a decent UOR activity and stability, i.e., reaching 1 A cm⁻² at a potential of 1.53 V. This work can inspire more insights into doping modification of UOR electrocatalysts.