Carbon Dots-Mediated\n0D/2D Interface Engineering in\nNi<sub>3</sub>S<sub>2</sub> Nanosheets for Efficient Electrocatalytic\nUrea Oxidation Coupled with Hydrogen Evolution

The\nurea oxidation reaction (UOR) has gained significant attention\nas an alternative to the oxygen evolution reaction (OER) for reducing\nenergy consumption during simultaneous hydrogen production and degradation\nof urea. However, developing efficient electrocatalysts for UOR remains\nchallenging due to the sluggish intrinsic kinetics involved in the\nsix-electron process. In this study, we report the use of carbon-dot-modified\nultrathin Ni<sub>3</sub>S<sub>2</sub> nanosheets on nickel foam (Ni<sub>3</sub>S<sub>2</sub>–CDs@NF) with a quasi-parallel structure\nfor urea-assisted electrocatalytic hydrogen evolution reaction (HER).\nThe zero-dimensional/two-dimensional (0D/2D) Ni<sub>3</sub>S<sub>2</sub>–CDs@NF catalyst exhibit high bifunctional catalytic activities\nwith a potential of 88 mV for HER and 1.35 V (vs RHE) for UOR at a\ncurrent density of 10 mA cm<sup>–2</sup>. By incorporating\nNi<sub>3</sub>S<sub>2</sub>–CDs@NF into a symmetrical electrolytic\ncell, low cell voltages of 1.67 and 1.81 V were acquired at the current\ndensities of 50 and 100 mA cm<sup>–2</sup> for HER||UOR, which\nare 110 and 280 mV lower than those of the nonreal HER||OER system,\nrespectively. Further electrochemical tests demonstrated that the\n0D/2D heterointerface between CDs and Ni<sub>3</sub>S<sub>2</sub> maximized\nthe exposure of surface-active sites while enhancing the electron\ntransfer rates and reaction kinetics. This study not only offers insights\ninto efficient carbon-dot-based electrocatalysts for urea electrolysis,\nbut also holds significant potential for applications in electrochemical\nenergy conversion and wastewater treatment.