Tweaking Nickel with Minimal Silver in a Heterogeneous Alloy of Decahedral Geometry to Deliver Platinum-like Hydrogen Evolution Activity

Five-fold intertwined AgxNi1-x (x=0.01-0.25) heterogeneous alloy nanocrystal (NC) catalysts, prepared through unique reagent combinations, are presented. With only ca. 5 at % Ag (AgNi-5), Pt-like activity has been achieved at pH 14. To reach a current density of 10 mA cm(-2) the extremely stable AgNi-5 requires an overpotential of 24.0 +/- 1.2 mV as compared to 20.1 +/- 0.8 mV for 20 % Pt/C, both with equal catalyst loading of 1.32 mg cm(-2). The turnover frequency (TOF) is as high as 2.1 H-2 s(-1) at 50 mV (vs. RHE). Site-specific elemental analyses show the Ag:Ni compositional variation, where the apex and edges of the decahedra are Ag-rich, thereby exposing Ni onto the faces to achieve maximum charge transport for an exceptional pH universal HER activity. DFT calculations elucidate the relative H-atom adsorption capability of the Ni centers as a function of their proximity to Ag atom.