Carbon dot-mediated NiO/NiS2 heterostructure nanoreactor for efficient electrocatalytic urea oxidation-coupled hydrogen production

Abstract

ABSTRACT Electrochemical hydrogen production is significantly hindered by the sluggish oxygen evolution reaction (OER), while the thermodynamically more favorable urea oxidation reaction (UOR) offers a promising alternative for simultaneous energy saving and environmental remediation. Herein, we report a carbon dot-mediated interfacial engineering strategy to construct a NiO/NiS2 heterostructure nanoreactor on nickel foam (CDs-NiO/NiS2@NF). The integrated NiO nanosheets, NiS2 nanoparticles, and CD-derived carbon-regulated interfacial domains synergistically facilitate charge transport and promote the dynamic formation of reconstructed NiOOH-rich active species during the urea oxidation reaction (UOR), thereby enabling efficient UOR-coupled hydrogen evolution. The optimized CDs-NiO/NiS2@NF achieves a low cell voltage of 1.53 V at 10 mA cm−2 in urea-assisted electrolysis, which is 140 mV lower than that of conventional water splitting, outperforming most transition metal electrocatalysts for UOR. Further testing shows that CDs-derived interfacial carbon species not only contribute to the enlarged electrochemical active surface areas and accelerated charge transfer but also promote the in-situ reconstruction of surface NiS2 into NiOOH. This work not only provides an effective heterostructure engineering strategy for developing low-cost Ni-based bifunctional electrocatalysts for UOR and HER but also enables the resource utilization of urea-rich wastewater with synergistic benefits of energy generation and environmental remediation.