PdGa Alloy Dynamics under CO2 Hydrogenation from Surface Organometallic Chemistry on a Chip and Operando Transmission Electron Microscopy

Industrial processes rely on the use of promoter elements to improve the performance of catalysts. De-spite considerable efforts, fundamental understanding on the origin of promotion remains elusive, partly due to the inherent complexity of catalytic systems. In this work, we develop a surface organometallic chemistry approach on an in situ MEMS chip for the preparation of tailored PdGa nanoparticles enabling to monitor the dynamic response of their structure and reactivity under a range of conditions – including CO2 hydrogenation – via operando (scanning) transmission electron microscopy. Upon air-exposure, the PdGa nanoparticles exhibit a core-shell structure, which vanishes after reduction in H2, forming alloyed PdGa nanoparticles exhibiting structural defects. Notably, under CO2 hydrogenation conditions (3:1 H2:CO2, 230 °C) at 1 bar, PdGa-GaOx interfaces are dynamically formed, while metha-nol is concomitantly detected. This study reveals the highly dynamic nature of PdGa catalysts and points out the pro-motional role of Ga in driving methanol synthesis under CO2 hydrogenation via the formation of MGa-GaOx interfaces.