Oxygen-vacancy-engineered urchin-like CoMoO4 epitaxially grown on partially oxidized Ti3C2 MXene anchored on nickel nanocones for an 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 CoMoO₄ nanostructure, featuring abundant redox-active Co and Mo sites that facilitate OH⁻ adsorption and conversion, was grown in situ on a partially TiO₂-derived Ti₃C₂ MXene framework (Ti₃C₂/TiO₂–CoMoO₄). The nanocomposite was pyrolyzed under nitrogen (p-Ti₃C₂/TiO₂–CoMoO₄) to enhance electronic conductivity, and activate catalytic sites, resulting in a defect-rich structure with abundant oxygen vacancies. Partial oxidation of Ti₃C₂ forms TiO₂ particles that prevent MXene restacking, stabilize the layered framework, and provide an ideal platform for in situ growth of CoMoO₄ nanostructures on Ti₃C₂/TiO₂, enhancing surface accessibility and facilitating ion transport. The resulting hierarchical p-Ti₃C₂/TiO₂–CoMoO₄ 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, p-Ti₃C₂/TiO₂–CoMoO₄–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 (j₀ = 96.25 mA cm⁻²), demonstrating outstanding catalytic activity and long-term operational stability. This work highlights that combining oxygen-vacancy-rich TiO₂-derived MXene with hierarchical, redox-active CoMoO₄ nanostructures on a NiNC scaffold provides a robust, highly accessible platform, offering a promising strategy for designing high-performance OER electrocatalysts.