Urea electrooxidation-boosted hydrogen production on nitrogen-doped porous carbon nanorod-supported nickel phosphide nanoparticles

Abstract

Urea electro-oxidation reaction (UEOR)-boosted water electrolysis can supplant the kinetics-restricted oxygen evolution reaction (OER) and provide an energy-saving method of hydrogen generation. However, low UEOR activity and the poisoning issue of the catalyst limit its practical application. Herein, a simple coordination reaction is used to synthesize the dimethylglyoxime-NiⅡ complex (DMG-NiⅡ), which efficiently serves as the initial precursor to synthesize nitrogen-doped carbon nanorod-supported nickel phosphide nanoparticle (Ni2P/N-Cnanorods) nanocomposites. The density functional theory calculations and electrochemical results reveal that nitrogen doping can weaken the adsorption of hydrogen and the generated CO2, resulting in an enhancement of hydrogen evolution reaction (HER) and UEOR activity. In addition, N-doping can also promote the generation of Ni3+, which can further promote the UEOR and HER performance. Concretely, the overpotential for the HER on Ni2P/N-Cnanorods-2h nanocomposites is only 201 mV at 10 mA cm−2, and the onset potential of the UEOR on Ni2P/N-Cnanorods-2h nanocomposites is only 1.34 V. Additionally, the Ni2P/N-Cnanorods nanocomposites also show excellent long-term stability due to the introduction of nitrogen-doped carbon material. Consequently, the symmetric Ni2P/N-Cnanorods-2h||Ni2P/N-Cnanorods-2h urea electrolyzer requires 1.41 V of electrolysis voltage for urea electrolysis, which can be applied in energy-saving H2 production and environment purification.