Sol–Gel Synthesized Co-Doped Ilmenite-NiTiO3 for Oxygen Evolution Reaction: Interplay of Inductive Effect and Crystal Structure

Abstract

The oxygen evolution reaction is key to advancing hydrogen production, energy storage, and sustainable energy technologies. In this study, we have explored the ilmenite-type Co-substituted NiTiO₃ as a promising OER catalyst in the alkaline electrolyte. Synergistic interaction between Ni and Co generates the inductive effect which enhances the ionicity of Ni─O bond leading to a greater overlap between Ni(3d) and O(2p) orbitals, resulting in a higher OER activity of the doped catalysts. Further presence of surface active Co³⁺ in the ilmenite structure plays a key role in the enhancement of OER activity of the catalyst. A systematic investigation of the OER activity of Ni_1-xCo_xTiO₃ (0 < x < 0.25) with different amounts of Co doping synthesized via sol–gel method is reported here. Among the compositions investigated, Ni_0.825Co₀.₁₇₅TiO₃ is the most active as it exhibits excellent activity with a Tafel slope of 56 mV dec⁻¹ and a overpotential of 395 mV at 10 mA cm⁻². This work presents the role of the inductive effect originating due to the difference in the electronegativity of neighboring cations, leading to alteration of the redox energies and facilitating the effective electron transfer required for the electrocatalytic OER, which can be further utilized to develop superior electrocatalysts.