Unraveling the effect of local dopant environment on NiO6 octahedron perturbation for enhanced oxygen evolution activity

The oxygen evolution reaction (OER) performance in cation-doped materials often exhibits a volcano-like relationship with dopant concentration. However, the influence of dopant content with its associated local environment on the electronic states of electrocatalysts remains unclear. Herein, V is incorporated into Ni(OH)2 to study the underlying mechanism. It is revealed that evenly distributed V can effectively perturb the NiO6 octahedron, leading to strong eg * band broadening and more electronic states around the Fermi level. This phenomenon significantly enhances the electron transfer from electrocatalysts to external circuits. Conversely, the aggregation of V at higher dopant concentration exerts weaker influence on perturbing the NiO6 octahedron. As a result of balance between V doping and aggregation, Ni0.95V0.05OOH, with the strongest NiO6 octahedron distortion, effectuating a remarkably low overpotential of 258 mV at 10 mA cm-2. Furthermore, such a structure activity relationship is also extended to Fe-doped Ni(OH)2, affirming the universality of the proposed mechanism.