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

Abstract

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.

NiFeOOH-Co9S8-Intercalated Nanostructure Arrays for Energy-Efficient H2 Production and Sulfion Oxidation at High Current Density

“…Encapsulation of active catalysts in the conductive coating is effectively utilized in literature to develop durable catalyst systems for the purpose. 24,25 FeN 4 encapsulated in porous carbon nitride displayed resistance to S n poisoning and durability up to 270 h. 26 The durability further increased to 460 h, when atomically dispersed Co in NC with CoN 4 sites were utilized for the purpose. 27 Furthermore, the presence of sulfide as a dopant improved the SOR efficiency.…”

“…One of the main challenges associated with the design of nanocatalyst-coated electrodes for SOR activity is surface protection from the deposition of elemental S n produced during the anodic process. Encapsulation of active catalysts in the conductive coating is effectively utilized in literature to develop durable catalyst systems for the purpose. , FeN 4 encapsulated in porous carbon nitride displayed resistance to S n poisoning and durability up to 270 h . The durability further increased to 460 h, when atomically dispersed Co in NC with CoN 4 sites were utilized for the purpose .…”