Using Ostwald Ripening to Fabricate Copper-Doped Double-Shelled CuCo2S4 Nanospheres: Driving the Transformation of the Electrocatalytic Oxygen Evolution Reaction Mechanism

Designing catalysts with optimized hollow morphologies to shift the oxygen evolution reaction mechanism from the adsorbed oxygen species mechanism to the lattice oxygen mechanism is key to high activity. We propose an innovative self-templating method based on the Ostwald ripening process, synthesizing double-shell hollow bimetallic sulfide nanospheres, CuCo₂S₄, through a one-step method using the synthesized template. The Jahn–Teller effect induced by copper doping enhances the metal–oxygen covalency by strengthening the overlap between Co 3d and O 2p orbitals, facilitating the surface transitions from Co₃O₄ to CoOOH and ultimately to CoO₂. Simultaneously, the symmetry of the Co–O octahedron is reduced from Oh to D4h, optimizing the reaction pathway and promoting efficient oxygen release. Copper doping exhibits lower energy barriers, favoring the LOM pathway, and this mechanism shift leads to a significant improvement in catalytic performance. The double-shell structure provides more electrochemical active sites while maintaining stability, aiding catalyst design in alkaline media.