Engineering high-valence nickel sites in Ni3S2/Ni3Se2 architectures enabling urea-assisted hydrogen evolution reactions

Abstract

A more thermodynamically favorable organic oxidation reaction should be used instead of the oxygen evolution reaction (OER) to avoid high power consumption. Implementing this technology requires the development of stable, highly efficient, and inexpensive electrocatalysts. This study reports the synthesis of a heterogeneous catalyst composed of Ni₃S₂ nanowires and Ni₃Se₂ nanosheets on nickel foam (Ni₃S₂@Ni₃Se₂/NF) using hydrothermal in situ growth and electrodeposition. The prepared Ni₃S₂@Ni₃Se₂/NF heterostructures demonstrate excellent hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) activities. The structural transformation and surface material changes of Ni₃S₂@Ni₃Se₂/NF during the UOR were observed using the in situ Raman method. The results reveal that the reconfiguration of the Ni-based catalyst is more intense and stronger in the UOR process, producing more Ni²⁺–O (β-Ni(OH)₂) and thereby generating more Ni³⁺–O (γ-NiOOH) via electrochemical oxidation. Furthermore, compared to other catalysts recently described, when Ni₃S₂@Ni₃Se₂/NF was used as both the anode and cathode in the battery, it only required a low 1.45 V voltage to attain a current density of 10 mA cm⁻². This work is a solid basis for producing hydrogen with low energy consumption from urea-assisted hydrogen evolution.