Partially Interstitial Silicon-Implanted Ruthenium as an Efficient Electrocatalyst for Alkaline Hydrogen Evolution.

To enhance the alkaline hydrogen evolution reaction (HER), it is crucial, yet challenging, to fundamentally understand and rationally modulate potential catalytic sites. In this study, we confirm that despite calculating a low water dissociation energy barrier and an appropriate H adsorption free energy (ΔG) at Ru-top sites, metallic Ru exhibits a relatively inferior activity for the alkaline HER. This is primarily because the Ru-top sites, which are potential H adsorption sites, are recessive catalytic sites, compared with the adjacent Ru-hollow sites that have a strong ΔG. To promote the transformation of Ru-top sites from recessive to dominant catalytic sites, interstitial Si atoms are implanted into the hollow sites. However, complete interstitial implantation leads to a high water dissociation energy barrier at the RuSi intermetallic surface. Thus, we present a partial interstitial incorporation strategy to form a Ru-RuSi heterostructure that not only converts the Ru-top sites from recessive to dominant catalytic sites but also preserves the low water dissociation energy barrier at the Ru surface. Moreover, the spontaneously formed built-in electric fields bidirectionally optimize the adsorption ability of the Ru sites, thereby greatly reducing the thermodynamic energy barrier and enhancing the alkaline HER.