Carbon-supported palladium catalysts for the direct synthesis of hydrogen peroxide from hydrogen and oxygen

Display Omitted * Carbon materials are efficient supports of Pd catalysts for H2O2 synthesis. * H2O2 formation activity depends on the structure and property of carbon supports. * Higher graphitic degree and lower COOH-group density favor H2O2 selectivity. * Metallic Pd is more efficient than PdO for H2O2 formation. * Smaller Pd nanoparticles exhibit higher activity and H2O2 selectivity. Twelve kinds of carbon materials were studied as supports of palladium catalysts for the direct synthesis of hydrogen peroxide. The correlation between the catalytic performance and the structure and physicochemical properties of carbon materials suggested the important roles of the graphitic structure and the surface function groups in the selective formation of H2O2. The carbon material with a higher degree of graphitic structure and a lower density of surface COOH groups provided higher H2O2 selectivity and productivity. The chemical state and the mean size of Pd particles also affected the catalytic behavior. Metallic Pd was more efficient than PdO, and the catalyst with a smaller mean size of Pd nanoparticles exhibited higher activity and H2O2 selectivity. The presence of a mineral acid rather than a halide promoter and an organic solvent contributed to the selective formation of H2O2.