Work-function-induced Interfacial Built-in Electric Fields in Os-OsSe 2 Heterostructures for Active Acidic and Alkaline Hydrogen Evolution.

Theoretical calculations unveil that the formation of Os-OsSe 2 heterostructures with neutralized work function (WF) perfectly balances the electronic state between strong (Os) and weak (OsSe 2 ) adsorbents and bidirectionally optimizes the hydrogen evolution reaction (HER) activity of Os sites, significantly reducing thermodynamic energy barrier and accelerating kinetics process. Then, heterostructural Os-OsSe 2 is constructed for the first time by a molten salt method and confirmed by in-depth structural characterization. Impressively, due to highly active sites endowed by the charge balance effect, Os-OsSe 2 exhibits ultra-low overpotentials for HER in both acidic (26 mV @ 10 mA cm -2 ) and alkaline (23 mV @ 10 mA cm -2 ) media, surpassing commercial Pt catalysts. Moreover, the solar-to-hydrogen device assembled with Os-OsSe 2 further highlights its potential application prospects. Profoundly, this special heterostructure provides a new model for rational selection of heterocomponents.