Construction of Mo<sub>2</sub>TiC<sub>2</sub>T<sub><i>x</i></sub> MXene as a Superior\nCarrier to Support Ru–CuO\nHeterojunctions for Improving Alkaline Hydrogen Oxidation

The sluggish anodic hydrogen oxidation reaction (HOR)\nof the hydroxide\nexchange membrane fuel cell (HEMFC) is a significant barrier for practical\nimplementation. Herein, we designed a catalyst of Mo<sub>2</sub>TiC<sub>2</sub>T<sub><i>x</i></sub> MXene-supported Ru–CuO\nheterojunctions (named as Ru–CuO/MXene). The XPS spectra and\nthe d-band center data of the different amounts of Cu of the Ru–CuO/MXene\nsuggested that there existed a strongly electronic metal–support\ninteraction between the active species and the substrate with MXene\nas the excellent carrier. Furthermore, the in situ electrochemical\nexperimental results (operando electrochemical impedance spectroscopy\nand in situ electrochemical Raman spectroscopy) and density functional\ntheory (DFT) calculations showed that Ru and CuO were the optimal\nadsorption sites for surface species *H and *OH, respectively, endowing\nRu–CuO/MXene with the ability to weaken the hydrogen binding\nenergy (HBE) and strengthen the hydroxide binding energy (OHBE). Remarkably,\nthe optimized catalyst modified an impressive HOR activity in the\n0.1 M KOH electrolyte with a kinetic and an exchange current density\nof 7.63 and 1.37 mA cm<sup>–2</sup> at 50 mV overpotential\n(vs. RHE), respectively, which were 1.98- and 1.2-fold higher than\nthose of commercial Pt/C (20 wt %). Finally, the as-prepared catalyst\nalso exhibited superior durability and exceptional CO antipoisoning\nability in 1000 ppm of the CO/H<sub>2</sub>-saturated 0.1 M KOH electrolyte.\nThis work provides an inspiring strategy to design high-activity HOR\nelectrocatalyst-based metallic Ru in alkaline environments.