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. (C) 2014 Elsevier Inc. All rights reserved.