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 (H2O2) synthesis (DHS). This study prepared hexagonal Pd3Sn2, orthorhombic Pd2Sn, and cubic Pd3Sn nanoparticles by solvothermal synthesis for DHS. The results reveal that hexagonal Pd3Sn2/TiO2 exhibits a superior DHS performance, as well as lower H2O2 degradation and hydrogenation, compared to orthorhombic Pd2Sn/TiO2, cubic Pd3Sn/TiO2, and Pd/TiO2. Detailed characterization and theoretical calculations indicate that hexagonal Pd3Sn2/TiO2 with higher PdO and SnOx contents presents lower adsorption and desorption capacities of hydrogen and oxygen than other catalysts. H2O2 can be rapidly generated once H2 and O2 are adsorbed on hexagonal Pd3Sn2/TiO2. High productivity and selectivity of H2O2 are achieved due to the lower energy barrier for the initial hydrogenation of *O2 to *OOH and the stability of H2O2 on hexagonal Pd3Sn2/TiO2 with the (102) facet. This study offers in-depth insights into Pd-based bimetallic alloys for DHS from the perspective of crystalline phase engineering.