Palladium–Tin Alloy Nanoparticles in Different Crystalline Phases for Direct Hydrogen Peroxide Synthesis

Understanding the performance differences of palladium–tin (Pd–Sn) nanocrystal phases lays the foundation to fine-tune their catalytic activity in direct hydrogen peroxide (H 2 O 2 ) synthesis (DHS). This study prepared hexagonal Pd 3 Sn 2, orthorhombic Pd 2 Sn, and cubic Pd 3 Sn nanoparticles by solvothermal synthesis for DHS. The results reveal that hexagonal Pd 3 Sn 2 /TiO 2 exhibits a superior DHS performance, as well as lower H 2 O 2 degradation and hydrogenation, compared to orthorhombic Pd 2 Sn/TiO 2, cubic Pd 3 Sn/TiO 2, and Pd/TiO 2 . Detailed characterization and theoretical calculations indicate that hexagonal Pd 3 Sn 2 /TiO 2 with higher PdO and SnO x contents presents lower adsorption and desorption capacities of hydrogen and oxygen than other catalysts. H 2 O 2 can be rapidly generated once H 2 and O 2 are adsorbed on hexagonal Pd 3 Sn 2 /TiO 2 . High productivity and selectivity of H 2 O 2 are achieved due to the lower energy barrier for the initial hydrogenation of *O 2 to *OOH and the stability of H 2 O 2 on hexagonal Pd 3 Sn 2 /TiO 2 with the (102) facet. This study offers in-depth insights into Pd-based bimetallic alloys for DHS from the perspective of crystalline phase engineering.