Effect of Hydrogen-Induced Metallization on Chemisorption

Hydrogen adsorption on transition-metal oxides can lead to surface metallization, but it is unclear how this change of surface property impacts the subsequent surface chemistry and catalysis. Herein, we investigate from the first-principles density functional theory how hydrogen-induced metallization affects the adsorption of common intermediates during the conversion of oxygenates and alkanes (such as alkoxy and alkyl groups) on the SrTiO₃(001) surface. We find that alkoxy adsorption is greatly enhanced by hydrogen-induced metallization and the strength increases with the hydrogen coverage. This is because hydrogen adsorption leads to electron donation to the Ti site, which then forms a bond with the alkoxy group. The enhancement is found to be nonlocal. The same chemistry is also responsible for the enhanced adsorption of alkyl groups on the Ti site, which renders a switch in the site preference from the O site on pristine SrTiO₃(001) to the Ti site on hydrogen-functionalized SrTiO₃(001). These insights shed light on the impact of hydrogen-induced metallization on the chemisorption on a perovskite surface.