Bifunctional Cobalt–Nickel Sulfide Nanoflowers as Electrocatalysts for Concurrent Energy-Efficient Hydrogen Production and Sulfur Recycling

Electrocatalytic water splitting is an important approach for sustainable and green production of hydrogen but is greatly hampered by the sluggish oxygen evolution reaction (OER). Therefore, developing a favorable alternative reaction to replace OER for both energy-efficient coproduction of hydrogen and value-added chemicals is highly desirable. Herein, a thermodynamically favorable sulfion oxidation reaction (SOR) electrocatalyzed by CoNi2S4 nanoflowers (CoNi2S4 NFs) is reported to couple with the hydrogen evolution reaction (HER) for energy-efficient hydrogen production and sulfur recovery. In this coupled system, only a low cell voltage of 0.3 V is required to produce hydrogen at 10 mA cm–2, much lower than that of water splitting (1.76 V). Meanwhile, S2– ions are selectively electrooxidized to sulfur with a high yield of 220.5 g h–1 m–2, realizing electrochemical upcycling of sulfur-containing pollutants. This strategy provides an attractive route for both energy-effective hydrogen generation and sulfur recycling.