Sodium-promoted Pd/TiO2 for catalytic oxidation of formaldehyde at ambient temperature.

Catalytic oxidation of formaldehyde (HCHO) to CO2 at ambient conditions is of great interest for indoor HCHO purification. Here, we report that sodium-doped Pd/TiO2 is a highly effective catalyst for the catalytic oxidation of HCHO at room temperature. It was observed that Na doping has a dramatic promotion effect on the Pd/TiO2 catalyst and that nearly 100% HCHO conversion could be achieved over the 2Na-Pd/TiO2 catalyst at a GHSV of 95000 h(-1) and HCHO inlet concentration of 140 ppm at 25 °C. The mechanism of the Na-promotion effect was investigated by using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), CO chemisorption, Temperature-programmed reduction by H2 (H2-TPR), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption of O2 (O2-TPD) methods. The results showed that Na species addition can induce and further stabilize a negatively charged and well-dispersed Pd species, which then facilitates the activation of H2O and chemisorbed oxygen, therefore resulting in the high performance of the 2Na-Pd/TiO2 catalyst for the ambient HCHO destruction.