S-doping engineering of Fe₂O₃/NiTe₂ heterostructures for electronic structure tuning to promote efficient urea...

The electrocatalytic water splitting of urea-containing wastewater represents a promising sustainable approach for hydrogen generation. Therefore, it is crucial to develop efficient and selective electrocatalysts. In this study, we synthesized Fe₂O₃/NiTe₂ heterostructures with controlled S doping through a two-step hydrothermal method. The resulting electrocatalyst features a hierarchical mesoporous structure, enhancing surface accessibility and increasing pore volume, which contributes to a three-dimensional open framework that facilitates gas transport. The construction of the heterojunction causes the local charge density at the interface between Fe₂O₃ and NiTe₂ to redistribute, significantly lowering the energy barrier of the intermediate adsorption/desorption process. The synergistic combination of S doping and heterojunction engineering enables exceptional bifunctional performance. In a solution of 1 M KOH with 0.33 M urea, the voltage of the urea oxidation reaction (UOR) decreased to 1.35 V vs. RHE at 100 mA cm^-2. When integrated into a two-electrode system for urea-assisted water splitting, the optimized S-Fe₂O₃/NiTe₂//S-Fe₂O₃/NiTe₂ assembly demonstrates outstanding operational efficiency, requiring only 1.64 V to maintain 100 mA cm^-2. Both experimental and computational analyses indicate that the enhanced activity is attributed to S doping adjusting the charge distribution in the heterojunction, forming favorable adsorption sites, lowering the energy barrier of the rate determining step, and consequently enhancing UOR performance. This study introduces the first S-doped Fe₂O₃/NiTe₂ heterostructure and highlights the synergy between S doping and the heterojunction design. This dual-regulation strategy effectively optimizes intermediate adsorption, achieving superior urea oxidation performance and providing new perspectives for electrocatalyst design through interface and doping engineering.