Gas-balancing adsorption strategy towards noble-metal-based nanowire electrocatalysts

Abstract

The preparation of noble metal nanowire electrocatalysts is greatly limited by the thermodynamically symmetric growth of face-centred-cubic structures. Here we report a gas-balancing adsorption strategy to prepare ultrathin palladium-, platinum- and gold-based nanowires (diameter < 2 nm) by controlling the competitive adsorption of in situ-generated H2 and CO. We prepare a library of 43 nanowires consisting of the three above-mentioned noble metals as hosts and 14 metals as guests. The ternary Pd85Pt8Ni7H41 nanowires with interstitial hydrogen exhibit impressive mass and specific activities of $$11.1 \, {\rm{A}}\,{\rm{mg}}_{{\rm{PGM}}}^{-1}$$ and 13.9 mA cm−2, respectively, for the oxygen reduction reaction at 0.9 VRHE in alkali. Operando X-ray absorption spectroscopy demonstrates breathing-like Pd–Pd bond length and strain changes at the applied potential, with Pd85Pt8Ni7H41 nanowires exhibiting larger compressive strain at relevant potentials, as well as low oxygen coverage. Theoretical calculations suggest that the interstitial hydrogen induces an s–d orbital interaction between palladium and hydrogen, which enhances the activity of the oxygen reduction reaction. The Pd85Pt8Ni7H41 nanowires can generate a high power density of 0.87 W cm−2 in H2/air (CO2-free) at 70 °C in an anion-exchange membrane fuel cell. Nanostructured design of mono- and multimetallic particles can be leveraged to achieve highly active catalysts. Now, a gas-balancing adsorption strategy is presented to prepare alloy nanowires with diameter of around 1 nm, whereby resulting catalysts achieve excellent performance for both anion- and proton-exhange membrane fuel cells.