Understanding the Role of Boron on the Interface Modulation of the Pd/TiO₂ Catalyst for Direct Synthesis of H₂O₂

Abstract

Rational modulation of metal–support interaction is an effective strategy to enhance the catalytic performance of a supported catalyst. Here, both the activity and selectivity for the direct H2O2 synthesis from H2 and O2 are enhanced by the doping of boron atoms at the interface of Pd and TiO2. With boron doping, the selectivity and productivity of H2O2 are remarkedly increased from 63.4% and 2.99 mol H2O2 gPd–1 h–1 to 80.1% and 3.65 mol H2O2 gPd–1 h–1 in a triphase semicontinuous reaction system at 10 °C and 0.1 MPa, respectively. The modulation effect of boron on the structure of Pd/TiO2 was thoroughly studied by using multiple techniques such as HRTEM, XRD, XPS, and in situ DRIFTS. The doped boron atom almost has no effect on the particle size of Pd nanoparticle, but enhances the strong metal–support interaction (SMSI) between the Pd particle and TiO2, which results in a change of the Pd2+/Pd0 ratio and surface Pd atoms configuration. An appropriate amount of boron atoms doped at the Pd–TiO2 interface increases the ratio of Pd2+ species, providing more active sites for the nondissociative activation of O2. Furthermore, the electronic effect between boron and Pd species increases the H2 adsorption and activation, resulting in simultaneous increases in H2O2 selectivity and productivity. This work highlights the significance of the modulation for metal–support interaction on direct H2O2 synthesis, which also provides an effective and economic route by interface doping to improve the performance of supported heterogeneous catalysts.