Razi University

The global energy crisis and the environmental consequences arising from the extensive consumption of fossil fuels have made the development of clean and sustainable energy technologies one of the most critical research priorities. In this context, hydrogen, as a clean energy carrier with high energy density and zero carbon emissions, has attracted considerable attention. However, conventional water electrolysis faces significant limitations in terms of energy consumption due to the sluggish kinetics of the oxygen evolution reaction (OER) and the requirement for high operating voltages. One effective strategy to reduce energy consumption in electrolysis is the replacement of OER with the oxidation of small organic molecules such as methanol, ethanol, and urea. These reactions not only exhibit faster kinetics and lower thermodynamic potentials but also enable the simultaneous production of hydrogen and value-added chemical transformations. In this regard, the design of bifunctional electrocatalysts with high activity, good stability, and low cost is of particular importance. In this study, a porous bifunctional electrocatalyst, CeS?@Ni?S?–NiS/NF, was successfully synthesized via the growth of a cerium-based metal–organic framework (Ce-MOF) on nickel foam followed by a sulfidation process. Initially, the Ce-MOF structure was directly grown on the surface of nickel foam at room temperature, and subsequently converted into the sulfide structure CeS?@Ni?S?–NiS/NF through a hydrothermal process in the presence of thioacetamide. X-ray diffraction (XRD) analysis confirmed the successful formation of CeS?, Ni?S?, and NiS phases. Field-emission scanning electron microscopy (FE-SEM) images revealed that the final structure possessed a layered, porous morphology composed of interconnected nanostructures, providing a high specific surface area. Energy-dispersive X-ray spectroscopy (EDS) and elemental mapping analyses confirmed the presence and uniform distribution of Ce, Ni, and S elements throughout the structure, indicating the successful formation of the sulfide nanocomposite. To evaluate the electrochemical performance of the synthesized electrode, cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and electrochemical active surface area (ECSA) measurements were conducted in alkaline media. The results demonstrated that the CeS?@Ni?S?–NiS/NF electrode exhibited significantly superior electrocatalytic activity compared to the control electrodes, including bare NF, Ni?S?–NiS/NF, Ce-MOF/NF, and MOF-free Ce–Ni–S/NF. The enhanced performance was attributed to the increased electrochemically active surface area, reduced charge transfer resistance, and improved reaction kinetics, arising from the synergistic interaction between cerium and nickel sulfides. Furthermore, the porous MOF-derived structure facilitated electrolyte diffusion and increased the number of accessible active sites.