Versatile NiFeCoS Multimetal Sulfide Enables Energy-Efficient Hydrogen Production Beyond Alkaline Water Splitting via Urea and Diverse Organic Oxidation Reactions

Abstract Electrocatalysts based on multimetal sulfides (MMS) are viewed as a promising material for electrochemical water-splitting applications. However, single-metal sulfides and bimetal sulfides generally provide poor catalytic performance, and the use of MMS in hydrogen production through breaking down of water has not been explored much. The introduction of two or more metal ion modifies electronic structure and exhibits strong synergistic interaction that improve catalytic properties. Herein, nickel–iron–cobalt (NFC)-based MMS was synthesized using a simple hydrothermal method to determine its efficiency for improving water-splitting performance. Structural analysis exhibited a crystalline phase of the prepared sulfide catalyst. SEM image of NFCS depicted a nanosheet-like structure with mapping, and the EDX spectrum shows uniform distribution of Ni, Fe, and Co elements. The synthesized NFCS exhibited good oxygen evolution reaction (OER) and hydrogen evolution reaction (HER); the required overpotential for OER was 316 mV and for HER was 209 mV at current densities of 10 mA cm–2. Lower Tafel slope values of 119 and 173 mV dec–1 for NFCS provide favorable reaction kinetic toward OER and HER, respectively. A two-electrode device was fabricated with NFCS as the working electrode that exhibited a constant applied potential of 1.89 V with a long-term stability test along with increased charge transfer kinetics. To further investigate the versatility of the catalyst, its anodic performance was initially evaluated in 1 M KOH + 0.33M urea. Replacing OER with UOR significantly reduced the anodic potential. Conclusively, this work reports a preliminary study of NFCS catalyst in a hybrid alkaline electrolyte medium containing various organic substrates. From the results obtained, methanol oxidation reaction (MOR) exhibits the best performance of the lowest anodic potential (113 mV) and applied cell voltage (1.61 V) that facilitates organic-assisted hydrogen production.