Tungsten-modified MXene-integrated Spinel Oxides as High-Performance and Stable Catalysts for Water/Seawater Oxidation

Abstract

Seawater electrolysis is a promising route for sustainable and large-scale green hydrogen production, but its practical implementation is severely hindered by chloride-induced corrosion and competing chloride oxidation at the anode. In this study, we report the systematic design and synthesis of a high-performance nonprecious electrocatalyst based on MXene-modified tungsten-integrated cobalt-magnesium spinel oxides (MnCo2O4@WO3-MXene) 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 Ti3C2Tx (MXene) nanosheets. Structural and phase analysis confirmed the formation of pure-face cubic MnCo2O4 with successful incorporation of WO3 and MXene 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 kinetics. Electrochemical studies demonstrated that MnCo2O4@WO3-MXene exhibits outstanding OER activity, delivering a low overpotential of 230 mV at 50 mA/cm2 in 1M KOH, with a Tafel slope of 64 mV/dec. Notably, with an alkaline seawater electrolyte, the electrocatalyst maintained exceptional activity, achieving an overpotential of 250 mV at 50 mA/cm2. Effective suppression of chlorine-related side reactions was verified by iodometric titration and UPLC-MS analysis, achieving a faradaic efficiency of ~99.9%. The catalyst exhibits outstanding stability at industrially relevant high current densities (500 mA/cm2) for 100 hours. The catalyst testing under the variable range of 25-60 °C exhibits improvement in the performance at elevated temperature, confirming the practicability across the dynamic temperature range. The excellent OER performance 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, the work provides a viable strategy for designing highly efficient and nonprecious electrocatalysts with chloride tolerance, advancing the practical feasibility of seawater electrolysis for sustainable hydrogen generation.