Enhancing the Hydrogen Activation Reactivity of Nonprecious Metal Substrates via Confined Catalysis Underneath Graphene.

Abstract

In the hydrogen evolution reaction (HER), the reactivity as a function of the hydrogen adsorption energy on different metal substrates follows a well-known volcano curve, peaked at the precious metal Pt. The goal of turning nonprecious metals into efficient catalysts for HER and other important chemical reactions is a fundamental challenge; it is also of technological significance. Here, we present results toward achieving this goal by exploiting the synergistic power of marginal catalysis and confined catalysis. Using density functional theory calculations, we first show that the volcano curve stays qualitatively intact when van der Waals attractions between a hydrogen adatom and different metal (111) surfaces are included. We further show that the hydrogen adsorption energy on the metal surfaces is weakened by 0.12-0.23 eV when hydrogen is confined between graphene and the metal surfaces, with Ni exhibiting the largest change. In particular, we find that the graphene-modified volcano curve peaks around Ni, whose bare surface already possesses moderate (or marginal) reactivity, and the corresponding HER rate of graphene-covered Ni is comparable to that of bare Pt. A hydrogen adatom has high mobility within the confined geometry. These findings demonstrate that graphene-covered Ni is an appealing effective, stable, and economical catalytic platform for HER.