Palladium hydride (PdHx) has been found to be one of the most promising catalysts for producing syngas by simultaneously performing the CO2 reduction reaction (CO2RR) and the hydrogen evolution reaction (HER). The previous experimental work reported PdHx has much better CO2RR electrochemical catalytic performance compared to metal Pd, which is because H concentrations and compositions of PdHx play a vital role in the effect on the performance. It is experimentally very difficult to study the stable atomic compositions and reaction mechanism at different H concentrations.<br/>Here, based on density functional theory (DFT) calculations, active learning cluster expansion (ALCE) equipped with Monte Carlo simulated annealing has been carried out to search for stable candidates of PdHx. DFT structures are used to train the cluster expansion (CE) model and find the ground state structures of each H concentration of PdHx from the CE convex hull. Furthermore, we further perform DFT calculations to verify the CE convex hull until we finally get the converged DFT convex hull for finding the ground state DFT candidates. After identifying stable structures, their H distributions in structures are further analyzed and their CO2RR activities are further studied by kinetic model to try to unveil the role of H. Their selectivities toward CO2 and H2 are also explored by the free energy describers of adsorbates.<br/>Finally, the stable compositions of PdHx are found from tremendous possible structures using ALCE method. Active and selective candidates are finally screened out for CO2RR.

Active learning cluster expansion studies of PdHx on CO2 reduction

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