Modulation electronic structure of NiS nanoarray induced by Fe, V doping for high efficiency water and urea electrolysis

Abstract

Exploring high-efficient and stable low-cost electrocatalysts is of significant importance for boosting the efficiency of water splitting and purifying urea-enriched wastewater. Herein, bimetallic doping strategy was adopted to obtain jasminum nudiflorum-like Fe, V doped NiS arrays (Fe, V-NiS/NF) via typical hydrothermal process and subsequent anion exchange reaction. The as-obtained Fe, V-NiS/NF array displays high catalytic activity and stability toward oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in alkaline media, with reduced overpotentials of 273 and 214 mV to deliver the current density of 50 mA cm−2 for OER and UOR, respectively. More notably, when employing Fe, V-NiS/NF as symmetric electrolytic cell for urea electrolysis, a low cell voltage of 1.45 V is needed at 10 mA cm−2, which is about 110 mV lower than the conventional water electrolysis. Meanwhile, the catalyst also displays superior stability for over 72 h. Such outstanding performance is attributed to the following points: (i) 3D porous flower-like structure facilitates the mass transfer and abundant exposure of active sites; (ii) in situ growth of catalysts on conductive substrate and the effective interface engineering of different composition shorten the charge transport pathways and expedite electron transfer. Density functional theory calculations demonstrate that the Fe and V dopants regulate the electronic environment of Ni sites and optimize the adsorption free energy of urea. This work provides a universal pathway to design high-efficient and non-noble electrocatalysts for H2 production in an energy-saving way via urea electrolysis.