Rational Strain Engineering in Delafossite Oxides for Highly Efficient Hydrogen Evolution Catalysis in Acidic Media

Filip Podjaski; Daniel Weber; Siyuan Zhang; Leo Diehl; Roland Eger; Viola Duppel; Esther Alarcon-Llado; Gunther Richter; Frederik Haase; Anna Fontcuberta i Morral; Christina Scheu; Bettina V. Lotsch

doi:10.1038/s41929-019-0400-x

paper

Rational Strain Engineering in Delafossite Oxides for Highly Efficient Hydrogen Evolution Catalysis in Acidic Media

arXiv:1903.10576 · doi:10.1038/s41929-019-0400-x

Abstract

The rational design of hydrogen evolution reaction (HER) electrocatalysts which are competitive with platinum is an outstanding challenge to make power-to-gas technologies economically viable. Here, we introduce the delafossites PdCrO $_{2}$ , PdCoO $_{2}$ and PtCoO $_{2}$ as a new family of electrocatalysts for the HER in acidic media. We show that in PdCoO $_{2}$ the inherently strained Pd metal sublattice acts as a pseudomorphic template for the growth of a strained (by +2.3%) Pd rich capping layer under reductive conditions. The surface modification continuously improves the electrocatalytic activity by simultaneously increasing the exchange current density j $_{0}$ from 2 to 5 mA/cm $_{g eo}^{2}$ and by reducing the Tafel slope down to 38 mV/decade, leading to overpotentials $η_{10}$ < 15 mV for 10 mA/cm $_{g eo}^{2}$ , superior to bulk platinum. The greatly improved activity is attributed to the in-situ stabilization of a $β$ -palladium hydride phase with drastically enhanced surface catalytic properties with respect to pure or nanostructured palladium. These findings illustrate how operando induced electrodissolution can be used as a top-down design concept for rational surface and property engineering through the strain-stabilized formation of catalytically active phases.