An efficient Pd/C catalyst design based on sequential ligand exchange method for the direct synthesis of H^sub 2^O^sub 2

A new catalyst preparation method involving the sequential ligand exchange of anionic palladium complexes to cationic complexes via the formation of palladium hydroxide intermediates is proposed. The novel method enables the electrostatic adsorption of an anionic palladium complex on the negatively charged carbon surface, and therefore makes it possible to obtain small and highly dispersed Pd nanoparticles. The H2O2 productivity and H2 selectivity of the ligand-exchanged catalyst were 16 and 3.6 times higher than those of the Pd/C catalyst prepared by using the same anionic palladium precursor. The strikingly different activities mainly attributed to the difference in the nanoparticle size and the oxidation state of Pd, which clearly indicates that the activity of Pd/C catalyst for the direct synthesis of H2O2 can be greatly improved by the sequential ligand exchange method.