On the mechanism of H2 activation over single-atom catalyst: An understanding of Pt1/WOx in the hydrogenolysis reaction

Abstract Owing to the atomic dispersion of active sites via electronic interaction with supports, single-atom catalysts (SACs) grant maximum utilization of metals with unique activity and/or selectivity in various catalytic processes. However, the stability of single atoms under oxygen-poor conditions, and the mechanism of hydrogen activation on SACs remain elusive. Here, through a combination of theoretical calculation and experiments, the stabilization of metal single atoms on tungsten oxide and its catalytic properties in H2 activation are investigated. Our calculation results indicate that the oxygen defects on the WO3(001) surface play a vital role in the stabilization of single metal atoms through electron transfer from the oxygen vacancies to the metal atoms. In comparison with Pd and Au, Pt single atoms possess greatly enhanced stability on the WOx(001) surface and carry negative charge, facilitating the dissociation of H2 to metal−H species (Hδ−) via homolytic cleavage of H2 similar to that occurring in metal ensembles. More importantly, the facile diffusion of Pt−H to the WOx support results in the formation of Bronsted acid sites (Hδ+), imparting bifunctionality to Pt1/WOx. The dynamic formation of Bronsted acid sites in hydrogen atmosphere proved to be the key to chemoselective hydrogenolysis of glycerol into 1,3-propanediol, which was experimentally demonstrated on the Pt1/WOx catalyst.