Construction of Mo2TiC2Tx MXene as a Superior Carrier to Support Ru–CuO Heterojunctions for Improving Alkaline Hydrogen Oxidation

The sluggish anodic hydrogen oxidation reaction (HOR) of the hydroxide exchange membrane fuel cell (HEMFC) is a significant barrier for practical implementation. Herein, we designed a catalyst of Mo2TiC2Tx MXene-supported Ru-CuO heterojunctions (named as Ru-CuO/MXene). The XPS spectra and the d-band center data of the different amounts of Cu of the Ru-CuO/MXene suggested that there existed a strongly electronic metal-support interaction between the active species and the substrate with MXene as the excellent carrier. Furthermore, the in situ electrochemical experimental results (operando electrochemical impedance spectroscopy and in situ electrochemical Raman spectroscopy) and density functional theory (DFT) calculations showed that Ru and CuO were the optimal adsorption sites for surface species *H and *OH, respectively, endowing Ru-CuO/MXene with the ability to weaken the hydrogen binding energy (HBE) and strengthen the hydroxide binding energy (OHBE). Remarkably, the optimized catalyst modified an impressive HOR activity in the 0.1 M KOH electrolyte with a kinetic and an exchange current density of 7.63 and 1.37 mA cm-2 at 50 mV overpotential (vs. RHE), respectively, which were 1.98- and 1.2-fold higher than those of commercial Pt/C (20 wt %). Finally, the as-prepared catalyst also exhibited superior durability and exceptional CO antipoisoning ability in 1000 ppm of the CO/H2-saturated 0.1 M KOH electrolyte. This work provides an inspiring strategy to design high-activity HOR electrocatalyst-based metallic Ru in alkaline environments.