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 PdCrO2, PdCoO2 and PtCoO2 as a new family of electrocatalysts for the HER in acidic media. We show that in PdCoO2 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 j0 from 2 to 5 mA/cmgeo2 and by reducing the Tafel slope down to 38 mV/decade, leading to overpotentials η10 < 15 mV for 10 mA/cmgeo2, 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.
@article{arxiv.1903.10576,
title = {Rational Strain Engineering in Delafossite Oxides for Highly Efficient Hydrogen Evolution Catalysis in Acidic Media},
author = {Filip Podjaski and Daniel Weber and Siyuan Zhang and Leo Diehl and Roland Eger and Viola Duppel and Esther Alarcon-Llado and Gunther Richter and Frederik Haase and Anna Fontcuberta i Morral and Christina Scheu and Bettina V. Lotsch},
journal= {arXiv preprint arXiv:1903.10576},
year = {2021}
}