Bubbles templated porous CeSe₂/Co₃Se₄ heterostructures supported on Ni foam for CO₂-free selective methanol oxidation to enhance green hydrogen production

This study investigates methanol-assisted water splitting (MAWS) as a promising alternative to conventional water electrolysis, with a focus on developing novel electrocatalysts to enhance the efficiency and selectivity of the methanol oxidation reaction (MOR) and the hydrogen evolution reaction (HER). A three-step synthesis process (electrodeposition, annealing, and selenization) was employed to synthesize the bubble-templated porous CeSe₂/Co₃Se₄ heterostructures supported on nickel foam (CeCoSe@NF). The electrocatalyst's activity and selectivity for MOR to formate were tested, and its performance was evaluated by Operando electrochemical impedance spectroscopy (EIS) and H-NMR. The optimized electrocatalyst required a potential less than 1.35 V vs. RHE to initiate the methanol oxidation reaction, achieving a current density of 100 mA cm⁻² at just 1.44 V vs. RHE under alkaline conditions. Operando EIS further confirms that MOR begins at 1.3 V for the porous CeCoSe@NF electrocatalyst, and MOR occurs similarly to OER at the low-frequency interface, indicating that MOR activity comes from the same adsorption intermediate (OH∗) as OER. For overall methanol-assisted water electrolysis, the optimized porous heterostructured CeO₂/Co₃O₄@NF electrode (CeCo@NF) without selenization showed good performance for HER, requiring 170 mV overpotential to attain 100 mA cm⁻² current density with near 98 % Faradaic efficiency. The two-electrode integrated electrolyzer (CeCoSe@NF as the anode and CeCo@NF as the cathode), with methanol-assisted splitting, operates at a cell voltage of only 1.52 V to reach 20 mA cm⁻², which is significantly lower than the 1.65 V required for traditional water splitting under the same conditions. The superior performance is attributed to the porous, dendritically interconnected nanostructure, synergistic heterointerfaces, and strong electronic coupling between the active components and the conductive Ni foam. This study highlights the potential of targeted methanol oxidation as a dual-purpose strategy for efficient energy-saving hydrogen generation and methanol upgrading to formate, contributing to the development of more sustainable energy systems.