Deposited PtGe Clusters as Active and Durable Catalysts for CO Oxidation

Control of CO emissions raises serious environmental concerns in the current chemical industry, as well as in nascent technologies based on hydrogen such as electrolyzers and fuel cells. As for now, Pt remains one of the state-of-the-art catalysts for the CO oxidation reaction, but unfortunately, it suffers from CO self-poisoning. Recently, Pt−Ge alloys were proposed to be an excellent alternative to reduce CO poisoning. This work investigates the impact of Ge content on the CO oxidation kinetics of Pt₄Ge_n subnanoclusters supported on MgO. A Ge concentration dependence of the reaction kinetics is found due to a strong synergy between Pt and Ge. Pt−Ge nanoalloys act as a bifunctional catalyst by displaying dual adsorption sites; i. e., CO is adsorbed on Pt whereas oxygen binds to Ge, forming an alternative oxygen source GeO_x. Besides, Ge alloying modifies the electronic structure of Pt (ligand effects) and reduces the affinity to CO. In this way, the competition between CO and O₂ adsorption and the overbinding of CO is alleviated, achieving a CO poisoning-free kinetic regime. Our calculations suggest that Pt₄Ge₃ is the optimal catalyst, evidencing that alloying composition is a parameter of extreme importance in nanocatalyst design. The work relies on global optimization search techniques to determine the accessibility of multiple structures at different conditions, mechanistic studies and microkinetic modeling.