Patterning the consecutive Pd(3) to Pd(1) on Pd(2)Ga surface via temperature-promoted reactive metal-support interaction

Atom-by-atom control of a catalyst surface is a central yet challenging topic in heterogeneous catalysis, which enables precisely confined adsorption and oriented approach of reactant molecules. Here, exposed surfaces with either consecutive Pd trimers (Pd(3)) or isolated Pd atoms (Pd(1)) are architected for Pd(2)Ga intermetallic nanoparticles (NPs) using reactive metal-support interaction (RMSI). At elevated temperatures under hydrogen, in situ atomic-scale transmission electron microscopy directly visualizes the refacetting of Pd(2)Ga NPs from energetically favorable (013)/(020) facets to (011)/(002). Infrared spectroscopy and acetylene hydrogenation reaction complementarily confirm the evolution from consecutive Pd(3) to Pd(1) sites of Pd(2)Ga catalysts with the concurrent fingerprinting CO adsorption and featured reactivities. Through theoretical calculations and modeling, we reveal that the restructured Pd(2)Ga surface results from the preferential arrangement of additionally reduced Ga atoms on the surface. Our work provides previously unidentified mechanistic insight into temperature-promoted RMSI and possible solutions to control and rearrange the surface atoms of supported intermetallic catalyst.