A Morphologically Engineered Robust Bifunctional CuCo₂O₄ Nanosheet Catalyst for Highly Efficient Overall Water Splitting

The development of an earth abundant, low-cost, and energy-efficient electrocatalyst with robust adhesion is highly essential for the generation of hydrogen fuel. Herein, the outstanding overall water splitting performance of a CuCo₂O₄ catalyst which is fabricated using a hydrothermal process is reported. The performance optimization is done through engineering the surface structure and size of the CuCo₂O₄ catalyst, without altering its chemical composition and crystallinity. Different solvents used in the hydrothermal growth tune the morphology of CuCo₂O₄ from porous 2-dimensional nanosheets through cubes and grains to agglomerated spheres. An optimized 2-dimensional nanosheet CuCo₂O₄ catalyst exhibits superior electrochemical performance for both hydrogen evolution reaction and oxygen evolution reaction, achieving the smallest overpotential of 115 and 290 mV versus a reversible hydrogen electrode, respectively, at 10 mA cm⁻² with excellent long-term stability under an alkaline electrolyte medium (1.0 m KOH). This highly stable and electrochemically active bifunctional electrocatalyst can deliver a cell voltage of 1.64 V at 10 mA cm⁻² under alkaline condition. Moreover, the correlation between electrochemical catalytic activity with solvent viscosity is manifested in the present study, which reveals that a change in morphologies causes the catalytically active surface area to vary and influences the intrinsic reaction kinetics.