Surface Phosphorus Grafting of Ti₃C₂T_<i>x</i> MXene as an Interface Charge “Bridge” for Efficient Electrocatalytic Hydrogen Evolution in All-pH Media

The interface electronic structure of heterogeneous catalysts can be modulated by changing the surface coordination configuration, which is crucial to their catalytic activity. Herein, a surface phosphorus-grafted Ti3C2Tx MXene platform anchored with an MoS2 nanoflake heterojunction electrocatalyst was assembled through a simple phosphorus-hydrothermal method. An interface charge “bridge” has been created by grafting uniform P atoms coordinated with the surface O atoms of Ti3C2Tx (P-Ti3C2Tx), resulting in an interface charge-transfer channel between P-Ti3C2Tx and MoS2. Based on the ultrafast transient absorption spectroscopy, the fastest electron-transfer kinetics from P-Ti3C2Tx to MoS2 (1.7 ps) and the slowest electron–hole recombination speed (28 ps) were obtained over MoS2@P-Ti3C2Tx than those over MoS2@O-Ti3C2Tx and MoS2@OP-Ti3C2Tx. Benefiting from the lower carrier transport activation energy, MoS2@P-Ti3C2Tx exhibited the stirring electrocatalytic activity toward hydrogen evolution in all-pH media, which delivered three low overpotentials of 48.6, 63.2, and 70.5 mV at 10 mA cm–2 toward the hydrogen evolution in alkaline, acid, and neutral media, respectively. Grafting an atomic scale “bridge” to create an electron-transfer channel proposes a new strategy to design an efficient pH-universal hydrogen evolution heterojunction electrocatalyst.