Boosting Water Splitting via Metal–Support Redox Interaction in Ce_1–xM_xO_2−δ (M = Co, Ni, Cu)

The efficiency of electrochemical water splitting is constrained by the anodic oxygen evolution reaction (OER), which suffers from high energy barriers, sluggish kinetics, and significant overpotential. Designing affordable and efficient electrocatalysts for the OER remains a key goal for advancing the hydrogen economy, with transitional metals like Co, Ni, and Cu gaining significant attention as promising alternatives due to their redox properties, abundance, and economy. The oxidation step of M n+ → M (n+1)+ (M = Co, Ni, Cu) is the key intermediate step that produces the active species (M-OOH) formation, and thereby lowers the energy barrier and enhances the kinetics of the OER. However, the oxidation of M n+ → M (n+1)+ creates charge-transfer orbitals near the Fermi energy level, which is fundamentally challenging. In this study, through structural and surface analyses, we demonstrate that the highly reducible CeO 2 support in the Ce 1– x M x O 2−δ solid-solution effectively facilitates the M n+ → M (n+1)+ oxidation process and the evolution of lattice oxygen during the OER. Among the three transition metals, the presence of the Ni 3+ species along with the surface oxygen vacancy promoted the formation of -OOH surface intermediates and maximized the OER activity in Ce 0.95 Ni 0.05 O 2−δ catalyst.