Vanadium-regulated nickel phosphide nanosheets for electrocatalytic sulfion upgrading and hydrogen production

The electrochemical sulfion oxidation reaction (SOR) is highly desirable to treat sulfion-rich wastewater and achieve energy-saving hydrogen production when coupled with the cathodic hydrogen evolution reaction (HER). Herein, we propose a thermodynamically favorable SOR to couple with the HER, and develop vanadium-doped nickel phosphide (V-Ni₂P) nanosheets for simultaneously achieving energy-efficient hydrogen production and sulfur recovery. V doping can efficiently adjust the electronic structure and improve intrinsic activity of Ni₂P, which exhibits outstanding electrocatalytic performances for the HER and SOR with low potentials of -0.093 and 0.313 V to afford 10 mA cm^-2. Remarkably, the assembled V-Ni₂P-based hybrid water electrolyzer coupling the HER with the SOR requires small cell voltages of 0.389 and 0.834 V at 10 and 300 mA cm^-2, lower than those required in a traditional water electrolysis system (1.5 and 1.969 V), realizing low-cost sulfion upgrading to value-added sulfur and hydrogen generation. This work provides an approach for energy-saving hydrogen production and toxic waste degradation.