Efficient photocatalytic propane oxidative dehydrogenation with ultralow loading of PdAg intermetallic nanoparticle...

Propane oxidative dehydrogenation (ODH) is a promising route for propylene production; however, the conventional thermal catalysts suffer from carbon deposit induced by harsh reaction conditions at high temperature. Developing a highly efficient light-driven photocatalytic system is a benign environmentally-friendly alternative. Herein, an ultra-low loading PdAg intermetallic compound (0.1 wt% Pd and 0.05 wt% Ag) supported on TiO₂ catalyst was employed via a facile photodeposition (PD) method. The introduction of Ag significantly improved the activation of oxygen driven by the unique interface of PdAg and TiO₂ with swift carrier transfer under light condition while Pd sites act as active site for the activation of C-H bonds. Moreover, X-ray absorption spectroscopy (XAS) clearly reveals electron-deficient Ag sites with electron transfer from Ag to Pd, conducive to the adsorption and activation of oxygen. Operando FT-IR and EPR spectra elucidate introduced Ag species progressively improved reactive oxygen radical intermediates derived from oxygen, which is responsible for the activation of propane. As a result, the optimized Pd_0.1Ag_0.05-TiO₂ catalyst displayed 3-fold enhancements in the propylene formation rate of 1649 μmol·g_cat^-1·h^-1 compared to that of Pd/TiO₂ at absence of Ag and O₂, assigned to the synergistic effect of Ag and O₂. Density functional theory results further confirm that incorporated Ag effectively reduced energy barrier (0.6 eV) for rate-determining step of proposed reaction pathway. This work provides mechanistic insights into synergistic effect of bimetallic photocatalysts and demonstrates a promising strategy for photocatalytic oxidative alkane conversion.