Surface Phosphorus\nGrafting of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene as an Interface Charge\n“Bridge” for Efficient Electrocatalytic Hydrogen Evolution\nin All-pH Media

The\ninterface electronic structure of heterogeneous catalysts can\nbe modulated by changing the surface coordination configuration, which\nis crucial to their catalytic activity. Herein, a surface phosphorus-grafted\nTi<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene platform\nanchored with an MoS<sub>2</sub> nanoflake heterojunction electrocatalyst\nwas assembled through a simple phosphorus-hydrothermal method. An\ninterface charge “bridge” has been created by grafting\nuniform P atoms coordinated with the surface O atoms of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> (P-Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>), resulting in an interface\ncharge-transfer channel between P-Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> and MoS<sub>2</sub>. Based on the ultrafast\ntransient absorption spectroscopy, the fastest electron-transfer kinetics\nfrom P-Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> to\nMoS<sub>2</sub> (1.7 ps) and the slowest electron–hole recombination\nspeed (28 ps) were obtained over MoS<sub>2</sub>@P-Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> than those over MoS<sub>2</sub>@O-Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> and\nMoS<sub>2</sub>@OP-Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>. Benefiting from the lower carrier transport activation energy,\nMoS<sub>2</sub>@P-Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> exhibited the stirring electrocatalytic activity toward hydrogen\nevolution in all-pH media, which delivered three low overpotentials\nof 48.6, 63.2, and 70.5 mV at 10 mA cm<sup>–2</sup> toward\nthe hydrogen evolution in alkaline, acid, and neutral media, respectively.\nGrafting an atomic scale “bridge” to create an electron-transfer\nchannel proposes a new strategy to design an efficient pH-universal\nhydrogen evolution heterojunction electrocatalyst.