Advanced Functional NiCo₂S₄@CoMo₂S₄ Heterojunction Couple as Electrode for Hydrogen Production via Energy-Saving Urea Oxidation

The urea oxidation reaction (UOR) is characterized by a lower overpotential compared to the oxygen evolution reaction (OER) during electrolysis, which facilitates the hydrogen evolution reaction (HER) at the cathode. Charge distribution, which can be modulated by the introduction of a heterostructure, plays a key role in enhancing the adsorption and cleavage of chemical groups within urea molecules. Herein, a facile all-room temperature synthesis of functional heterojunction NiCo₂S₄/CoMo₂S₄ grown on carbon cloth (CC) is presented, and the as-prepared electrode served as a catalyst for simultaneous hydrogen evolution and urea oxidation reaction. The Density Functional Theory (DFT) study reveals spontaneous transfer of charge at the heterointerface of NiCo₂S₄/CoMo₂S₄, which triggers the formation of localized electrophilic/nucleophilic regions and facilitates the adsorption of electron donating/electron withdrawing group in urea molecules during the UOR. The NiCo₂S₄/CoMo₂S₄// NiCo₂S₄/CoMo₂S₄ electrode pair required only a cell voltage of 1.17 and 1.18 V to deliver a current density of 10 and 100 mA cm^-2 respectively in urea electrolysis cell and display very good stability. Tests performed in real urine samples show similar catalytic performance to urea electrolytes, making the work one of the best transition metal-based catalysts for UOR applications, promising both efficient hydrogen production and urea decomposition.