Engineering Amorphous Cobalt-Nickel Phosphate Nanostructures on Exfoliated Graphite: A Molecular Precursor-Driven Route to High-Performance Alkaline Water Splitting Catalysts.

The development of earth-abundant, bifunctional electrocatalysts is essential for advancing alkaline water electrolysis as a sustainable hydrogen production technology. Herein, a low-temperature molecular precursor strategy is employed to synthesize an amorphous cobalt-nickel phosphate (Co─Ni─Pi) catalyst anchored on exfoliated graphite (EG). The use of thermolytically labile [(M(tmeda)(H₂O)₄)(dtbp)₂] (M = Co, Ni) complexes enables in situ formation of a redox-active, amorphous bimetallic phosphate phase under solvothermal conditions. Structural and spectroscopic analyses confirm the homogeneous dispersion of phosphate nanoparticles and the presence of mixed-valent Co²⁺/Co³⁺ and Ni²⁺/Ni³⁺ species. Electrochemical investigations reveal enhanced bifunctional performance of Co─Ni─Pi/EG toward both the oxygen evolution reaction and the hydrogen evolution reaction in alkaline media outperforming the monometallic analogues. The catalyst also achieves overall water splitting at 1.70 V cell voltage with excellent stability for 72 h in a two-electrode configuration. This study underscores the effectiveness of molecular precursor engineering, heterometallic synergy and carbon scaffold integration in designing robust, low-cost electrocatalysts for renewable hydrogen production.