Tungsten-modified MXene-integrated spinel oxides as high-performance and stable catalysts for water/seawater oxidation

Abstract

Seawater electrolysis offers a promising strategy for sustainable and large-scale production of green hydrogen; however, its practical application is significantly hindered by chloride-induced corrosion and competing chloride oxidation at the anode. In this work, the systematic design and synthesis of a high-performance non-precious electrocatalyst based on MXene-modified tungsten-integrated cobalt–magnesium spinel oxides (MnCo₂O₄@WO₃-MXene) is reported for efficient alkaline seawater electrolysis. The ternary hybrid catalyst was prepared via a facile, comprehensive strategy, enabling intimate and phase interfacial coupling between spinel MnCo₂O₄, WO₃, and Ti₃C₂T_x (MXenes) nanosheets. Structural and phase analysis confirmed the formation of pure-phase cubic MnCo₂O₄ with successful incorporation of WO₃ and MXenes without disrupting the parent lattice. Rietveld refinement revealed an elongated Co–O bond length in the hybrid catalyst, indicative of weakened metal–oxygen interaction that favors oxygen evolution reaction (OER) kinetics. Electrochemical analysis reveals that MnCo₂O₄@WO₃-MXene exhibits excellent catalytic performance, delivering an overpotential of 230 mV to achieve a current density of 50 mA cm⁻² in 1 M KOH, along with a Tafel slope of 64 mV dec⁻¹. Notably, in an alkaline seawater electrolyte, the catalyst retains its high activity by achieving an overpotential of 250 mV at the same current density. Iodometric titration and UPLC-MS analysis confirm the separation of chlorine-related side reactions, achieving a faradaic efficiency of ∼99.9%. The catalyst exhibits outstanding stability at industrially relevant high current densities (500 mA cm⁻²) for 100 hours. Catalyst testing in the variable range of 25–60 °C exhibits improvement in performance at elevated temperature, confirming the practicability across a dynamic temperature range. The excellent catalytic activity is attributed to the combined effect of MXene-induced rapid charge transport, improved active site accessibility, and a WO₃-enabled corrosion-resistive passivation layer for structural stability. Overall, this work presents an effective pathway for the design of highly efficient electrocatalysts with chloride tolerance, advancing the practical feasibility of seawater electrolysis for sustainable hydrogen generation.