Oxygen-Vacancy-Engineered Urchin-Like CoMoO 4 Epitaxially Grown on Partially Oxidized Ti 3 C 2 MXene Anchored on Nickel Nanocones for Efficient Oxygen Evolution Reaction

Abstract

Efficient oxygen evolution electrocatalysts are essential for advancing alkaline water-splitting technologies. In this study, an oxygen-vacancy-rich, urchin-like CoMoO 4 nanostructure, featuring abundant redox-active Co and Mo sites that facilitate OH -adsorption and conversion, was grown in situ on a partially TiO 2 -derived Ti 3 C 2 MXene framework (Ti 3 C 2 /TiO 2 -CoMoO 4 ). The nanocomposite was pyrolyzed under nitrogen (p-Ti 3 C 2 /TiO 2 -CoMoO 4 ) to enhance electronic conductivity, and activate catalytic sites, resulting in a defect-rich structure with abundant oxygen vacancies. Partial oxidation of Ti 3 C 2 forms TiO 2 particles that prevent MXene restacking, stabilize the layered framework, and provide an ideal platform for in-situ growth of CoMoO 4 nanostructures on the Ti 3 C 2 /TiO 2 , enhancing surface accessibility and facilitating ion transport. The resulting hierarchical p-Ti 3 C 2 /TiO 2 -CoMoO 4 electrocatalyst was then integrated onto Ni nanocones (NiNCs) grown on Ni foam, forming a mechanically robust and highly conductive electrode. This configuration strengthens electronic coupling, optimizes adsorption of oxygen evolution reaction (OER) intermediates, and ensures efficient charge transfer. Benefiting from these synergistic structural and electronic features, the p-Ti 3 C 2 /TiO 2 -CoMoO 4 -NiNC-NF delivers an overpotential of 190 mV at 10 mA cm -2 , a Tafel slope of ~56.1 mV dec -1 , and a significantly enhanced exchange current density (j 0 =96.25 mA cm -2 ), demonstrating outstanding catalytic activity and long-term operational stability. This work highlights that combining oxygen-vacancy-rich TiO 2 -derived MXene with hierarchical, redox-active CoMoO 4 nanostructures on a NiNC scaffold provides a robust, highly accessible platform, offering a promising strategy for designing high-performance OER electrocatalysts.