Porous nickel sulfide nanorods serve as a multifunctional electrocatalyst for the hydrogen evolution reaction, urea electrooxidation reaction, and nitrate reduction reaction

Abstract

Rational design and simple synthesis of multifunctional electrocatalysts have significant implications across various scientific and industrial fields. In this work, we successfully synthesized nickel sulfide catalysts featuring a one-dimensional porous nanorod morphology (NiS-NRs) through a hard-template-high-temperature calcination approach. In this method, nickel-dimethylglyoxime complex nanorods ((DMG)₂Ni) served as a precursor and inexpensive thiourea as a sulfur source. The urea electrooxidation reaction (UEOR) in water electrolysis presents an opportunity to replace the kinetics-limited oxygen evolution reaction (OER), offering an energy-efficient means of hydrogen production. For the urea electrooxidation reaction, an overvoltage of 1.37 V (versus RHE) was required to achieve a current density of 10 mA cm⁻². Similarly, for the hydrogen evolution reaction, a modest overvoltage of 255 mV resulted in a current density of 10 mA cm⁻². In a two-electrode system, the NiS-NR‖NiS-NR urea electrolyzer demanded a potential of 1.24 V at 1 mA cm⁻², surpassing the aqueous electrolyzer requirement (1.41 V vs. RHE). Meanwhile, the as-prepared NiS-NRs also showed a high nitrate reduction reaction (NO₃RR) performance, with a high NH₃ yield rate (0.513 mmol h⁻¹ mg_cat⁻¹) at −0.65 V vs. RHE. These results verified that the high-temperature calcination process employing a hard template effectively preserved the one-dimensional morphology of the initial template. The resultant nickel sulfide catalysts exhibit commendable electrocatalytic performance for urea electrooxidation, hydrogen evolution and nitrate reduction reactions.