Stabilizing Pt Single Atoms through Pt-Se Electron Bridges on Vacancy-enriched Nickel Selenide for Efficient Electrocatalytic Hydrogen Evolution.

Rational design of Pt single-atom catalysts provides a promising strategy to significantly improve the electrocatalytic activity for hydrogen evolution reaction. In this work, we presented a novel and efficient strategy for utilizing the low electron-density region of substrate to effectively trap and confine high electron-density metal atoms. The Pt single-atom catalyst supported by nickel selenide with rich vacancies was prepared via a hydrothermal-impregnation stepwise approach. Through experimental testation and DFT theoretical calculation, we confirm that Pt single atoms are well distributed at cationic vacancies of nickel selenide with loading amount of 3.2 wt. %. Moreover, the atomic Pt combined with the high electronegative Se to form Pt-Se bond as a "bridge" between single atoms and substrate for fast electron translation. This novel catalyst shows an extremely low overpotential of 45 mV at 10 mA cm and an excellent stability over 120 h. Furthermore, the nickel selenide supported Pt SACs exhibits long-term stability for practical application, which maintains a high current density of 390 mA cm over 80 h with a retention of 99 %. This work points a promising direction for designing single atoms catalysts with high catalytic activity and stability for advanced green energy conversion technologies.