Pd-TiO₂ nanoparticles supported on reduced graphene oxide: Green synthesis and improved electrocatalytic performance for methanol oxidation

Uniform Pd and TiO₂ nanoparticles supported on reduced graphene oxide (Pd-TiO₂/RGO) as novel electrocatalyst has been synthesized by an easy green route via a two-step process using deionized water as solvent merely, first hydrothermal synthesis and then reducing reaction under room temperature. Scanning electron microscopy images proved that TiO₂ nanoparticles were anchored on RGO, while transmission electron microscopy images showed that Pd and TiO₂ nanoparticles were with an average size of 8 nm and 11 nm respectively. Cyclic voltammograms tests for the hybrid catalysts showed that the electrochemically active surface area of Pd-TiO₂*1/RGO hybrid catalyst was 105.0 m²/g_Pd, 5.7 and 3.6 times larger than that of Pd/C and Pd/RGO catalysts respectively. It also showed the highest oxidation peak current at the value of 764.1 A/g_Pd in this work. Meanwhile, chronoamperometry tests confirmed that the stability of Pd-TiO₂/RGO hybrid catalysts were increased with the addition of TiO₂ compared with Pd/C and Pd/RGO catalysts. X-ray photoelectron spectroscopy was utilized to further study the interaction between Pd and TiO₂, which showed a midification of electronic structure of Pd and TiO₂. It can be inferred that the improved electrocatalytic activity and stability of Pd-TiO₂/RGO hybrid catalysts can be ascribed to the unique support (graphene) with high specific surface area and excellent electrical conductivity, as well as the additive (titanium dioxide) which brings in synergistic effect with palladium.