Cobalt on Tungsten Titanium Carbide MXene: A Electrocatalyst for Industrial-Scale High Current Density Alkaline Hydrogen Evolution Reaction

Abstract Hydrogen (H₂) is considered the most promising clean energy source to replace conventional fossil fuels. Despite the exceptional catalytic activity of Pt-group metals, the high cost and relatively low durability of these noble metal-based catalysts remain key bottlenecks for sustainable hydrogen production at the industrial scale. In this report, we synthesized a new type of MXene, tungsten titanium carbide (W₂TiC₂). By loading cobalt (Co) onto the surface of W₂TiC₂, we developed a highly effective and stable catalyst for alkaline hydrogen evolution reaction (HER). The optimized catalyst exhibited a small overpotential of 62.58 mV at 10 mA/cm² and a low Tafel slope of 44.34 mV/dec. At high current density of 100 mA/cm² and 1000 mA/cm², the low overpotentials of 191.18 mV and 407.72 mV were achieved, significantly outperforming the commercial Pt/C electrode. Under both current ranges, our catalyst exhibited excellent stability of 500 h at 10 mA/cm² and for 100 h at 1000 mA/cm² without any obvious degradation. In flow cell tests, by pairing with Ni foam, our catalyst also required much lower cell voltage than commercial Ni foam||Pt/C and maintained ~ 100% H₂ faradaic efficiency over the 15h continuous tests from 100 to 400 mA/cm². X-ray absorption near edge structure (XANES) demonstrated a temperature induced redistribution of Co on MXenes from single sites and large nanoparticles (NPs) to uniform small NPs. Density functional theory (DFT) calculations, combined with X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS), revealed that the HER activity was sensitive to the coordination environment of Co on W₂TiC₂, and the Co-W interface is the likely HER active site . This work sheds light on structure design and utilization of metal-support interaction (MSI) in MXene-supported metal catalysts for the efficient electrochemical water splitting at industrial scale.