Toward Understanding of the Support Effect on Pd1 Single-Atom-Catalyzed Hydrogenation Reactions

Metal single-atom catalysts (SACs) have received significant attention in the catalysis field due to maximized atom efficiency and their unique catalytic properties. The support could have prominent influences on the catalytic performance. However, the support effect on metal SACs has been much less explored. We found that the Pd1/graphene catalyst exhibited remarkably higher activity than Pd1/C3N4 in both reactions, but the alkene selectivity showed a different trend. In hydrogenation of acetylene, considerably higher ethylene selectivity was observed on Pd1/C3N4. While in hydrogenation of 1,3-butadiene, Pd1/graphene showed a significantly higher 1-butene selectivity, along with less n-butene isomer production. Higher activity of Pd1/graphene could be related with the lower Pd valence state revealed by X-ray photoemission spectroscopy and higher accessibility Pd1 single atoms due to the slower coking rate. Meanwhile, different selectivities on these two samples might be attributed to the porosity and aci...