Lattice oxygen activation enabled by high-valence metal sites for enhanced water oxidation

Anodic oxygen evolution reaction (OER) is recognized as kinetic bottleneck in water electrolysis. Transition metal sites with high valence states can accelerate the reaction kinetics to offer highly intrinsic activity, but suffer from thermodynamic formation barrier. Here, we show subtle engineering of highly oxidized Ni⁴⁺ species in surface reconstructed (oxy)hydroxides on multicomponent FeCoCrNi alloy film through interatomically electronic interplay. Our spectroscopic investigations with theoretical studies uncover that Fe component enables the formation of Ni⁴⁺ species, which is energetically favored by the multistep evolution of Ni²⁺→Ni³⁺→Ni⁴⁺. The dynamically constructed Ni⁴⁺ species drives holes into oxygen ligands to facilitate intramolecular oxygen coupling, triggering lattice oxygen activation to form Fe-Ni dual-sites as ultimate catalytic center with highly intrinsic activity. As a result, the surface reconstructed FeCoCrNi OER catalyst delivers outstanding mass activity and turnover frequency of 3601 A g_metal^-1 and 0.483 s^-1 at an overpotential of 300 mV in alkaline electrolyte, respectively.