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

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 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.

Effect of Gas Environment on Metal‐Support Interactions of Supported Metal Catalysts

“…The composition of these compounds is highly dependent on gas atmospheres. [94,95] The weak interaction typically involves charge transfer between metal nanoparticles and support interface, termed electronic metal-support interaction (EMSI). [8,96] The magnitude and direction of charge transfer depend on Fermi level differences between the metal nanoparticle and the support, aiming for electron chemical potential equilibration.…”

“…Recent studies have suggested that adjusting the reduction temperature can fine-tune the composition of bimetallic alloys. Niu et al [95] subjected PdO/Ga 2 O 3 to different temperatures ranging from 100 °C to 600 °C in an H 2 /He atmosphere. They observed that PdO was reduced to different phases: Pd at 100 °C to 200 °C, Pd 2 Ga at 300 °C to 500 °C, and a combination of Pd 2 Ga and Pd 5 Ga 3 at 600 °C due to RMSI between Pd and Ga 2 O 3 .…”

Redox Dynamics and Surface Structures of an Active Palladium Catalyst during Methane Oxidation

“…(22)(23)(24)(25) Among these techniques, in situ transmission electron microscopy (TEM) is a particularly powerful tool for studying the atomic structure and dynamic behavior of materials as it offers a real-time and real-space imaging of catalysts with high temporal and spatial resolution under external stimuli. (26)(27)(28)(29)(30)(31)(32)(33) In particular, the combined use of online mass spectrometry (MS) with in situ TEM has demonstrated a great potential in improving our understanding of the structure-performance relationships in catalytic processes, for instance, H 2 or CO oxidation. (34)(35)(36)(37) Yet, the majority of previous in situ / operando studies of Pd-based methane oxidation catalysis have used spectroscopic techniques with only a limited spatial resolution (e.g., X-ray absorption spectroscopy and X-ray photoemission spectroscopy).…”

In Situ Visualization and Mechanistic Understandings on Facet-Dependent Atomic Redispersion of Platinum on CeO2

“…23−27 We have also studied the interface mediated formation of PdZn and the refacetting of Pd 2 Ga NPs under a reducing atmosphere at elevated temperatures. 28,29 The combination of in situ TEM with spectroscopy techniques is therefore key to deepening the understanding of Pt redispersion on CeO 2 . Herein, we investigated the redispersion of Pt on CeO 2 , focusing on the impact of CeO 2 facets on redispersion at the atomic level.…”

“…Atomic-scale control and mechanistic insights into redispersion highly rely on recognizing the dynamic structural evolution of Pt on CeO 2 under various chemical environments. The advent of in situ techniques has markedly advanced the observation of catalyst structure and behavior during reactions. , In situ transmission electron microscopy (TEM), in particular, is advantageous for monitoring the surface/interface dynamics of nanocatalyst at the atomic level. , This method has not only enabled direct observation of phenomena like Pt NP refacetting during CO oxidation but also revealed the critical role of support material properties and reaction environments in influencing the dynamic sintering and structural evolution of metallic NPs during catalytic processes. − We have also studied the interface mediated formation of PdZn and the refacetting of Pd 2 Ga NPs under a reducing atmosphere at elevated temperatures. , The combination of in situ TEM with spectroscopy techniques is therefore key to deepening the understanding of Pt redispersion on CeO 2 .…”