Patterning the consecutive Pd<sub>3</sub> to Pd<sub>1</sub> on Pd<sub>2</sub>Ga surface via temperature-promoted reactive metal-support interaction.

Niu, Yiming; Wang, Yongzhao; Chen, Junnan; Li, Shiyan; Huang, Xing; Willinger, Marc-Georg; Zhang, Wei; Liu, Yuefeng et al. · Sci Adv · 2022

basic_science · Level V

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Abstract

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<sub>3</sub>) or isolated Pd atoms (Pd<sub>1</sub>) are architected for Pd<sub>2</sub>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<sub>2</sub>Ga NPs from energetically favorable (013)/(020) facets to (011)/(002). Infrared spectroscopy and acetylene hydrogenation reaction complementarily confirm the evolution from consecutive Pd<sub>3</sub> to Pd<sub>1</sub> sites of Pd<sub>2</sub>Ga catalysts with the concurrent fingerprinting CO adsorption and featured reactivities. Through theoretical calculations and modeling, we reveal that the restructured Pd<sub>2</sub>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.