Abstract: Series of heterogeneous interfacial engineered TiO₂ (C-TiO₂) with controllable carbon content were facilely synthesized by incipient-wet impregnation using glucose and subsequent thermal carbonization. The obtained C-TiO₂ were used as catalytic supports to load Pd nanoparticles for H₂O₂ direct synthesis from H₂ and O₂. The as-prepared samples were systematically studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), air isothermal microcalorimeter, temperature-programmed reduction of H₂ (H₂-TPR), and so on. The catalytic results showed that H₂O₂ productivity and H₂O₂ selectivity of Pd/C-TiO₂ firstly rose with increasing carbon content and then declined. Pd/C-TiO₂ catalyst with 1.89 wt% of carbon content showed the best catalytic performance that had 61.2% of selectivity and 2192 mmol H₂O₂/g_Pd/h of productivity, which were significantly better than those of pristine Pd/TiO₂ (45.2% and 1827 mmol H₂O₂/g_Pd/h). Various characterization results displayed that the carbon species were heterogeneously dispersed on TiO₂ surface. Moreover, no obvious geometric transformation in supports and Pd nanoparticles were observed among different catalysts. The superficial hydrophobicity of Pd/C-TiO₂ was gradually promoted with increasing carbon content, which led to the corresponding decrease in adsorption energy of H₂O₂ with catalysts. According to structure-performance relationship analyses, the heterogeneous interfacial engineering of carbon could maintain the interaction of Pd nanoparticles with TiO₂ and simultaneously accelerate the H₂O₂ desorption. Both factors further determined the excellent H₂O₂ direct synthesis performance of Pd/C-TiO₂.

Key words: Direct synthesis of H₂O₂, TiO₂, Carbon, Heterogeneous interfacial engineering, Pd