Lead regulation of electronic properties and local structure of palladium (111) facet for enhanced direct hydrogen peroxide synthesis.

Direct synthesis of hydrogen peroxide (DSHP) from oxygen (O₂) and hydrogen (H₂) offers a promising alternative to anthraquinone oxidation for hydrogen peroxide (H₂O₂) production, yet challenges remain in achieving high selectivity and productivity. In this study, palladium octahedral nanoparticles (Pd ONPs) exposing Pd(111) facets were first synthesized, followed by the introduction of lead (Pb) atoms onto these facets to construct Pb-Pd(111) surface alloy structures (Pd@Pd-Pbx ONPs) for efficient DSHP. Characterization results indicated that the introduction of Pb atoms increased the electron density of Pd atoms and significantly reduced the number of low-coordinated Pd atoms. Density functional theory (DFT) calculations confirmed that the high electron density in Pd atoms downshifted their d-band center, thereby enhancing the adsorbed O₂ (O₂*) and hydroperoxyl (OOH*) hydrogenation and promoting the adsorbed H₂O₂ (HOOH*) desorption from Pd active sites, which was a key step in the formation of H₂O₂. Furthermore, the different coordination environments and electronic properties of Pd atoms that were close to Pb as opposed to those that were farther away produced a unique tilted adsorption configuration for O₂*, OOH*, and HOOH* on the Pd-Pb(111) surface, effectively inhibiting OO bond dissociation. As a result, the TiO₂-loaded Pd@Pd-Pb₄ ONPs (Pd@Pd-Pb₄/TiO₂) catalyst achieved an H₂O₂ selectivity of 80.6 % and a productivity of 6258.7 mmol g_Pd^-1h^-1 in the DSHP. This study underscores the impact of Pd catalyst surface modification on DSHP performance and provides valuable insights into the structure-performance relationship in bimetallic catalysts.