Visible-Light-Driven CO Preferential Oxidation over In Situ Photodeposited Au/TiO2 Catalysts in H2-Rich Atmospheres.

At low temperatures, the preferential removal of CO from the fuel feed of PEMFC is a critical factor for ensuring the optimal performance of fuel cells. In this study, Au/TiO2-PD and Au/TiO2-DP catalysts were synthesized via in situ photo-deposition and deposition-precipitation methods, respectively. The catalytic performance for CO preferential oxidation was evaluated in a hydrogen-rich atmosphere, and the effects of visible light irradiation on catalytic activity and selectivity were systematically investigated. The Au/TiO2-DP catalyst exhibited a relatively low CO conversion under dark conditions in the hydrogen-rich atmosphere, while visible light irradiation significantly enhanced its CO oxidation activity and selectivity. In contrast, the Au/TiO2-PD catalyst achieved a high CO oxidation conversion, but suffered from low CO oxidation selectivity; moreover, visible light exerted a weak inhibitory effect on its selectivity. Combined characterization results from temperature-programmed desorption (TPD), temperature-programmed surface reaction (TPSR), in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) and in situ electron paramagnetic resonance (EPR) revealed that the Au/TiO2-PD catalyst possessed stronger hydrogen adsorption, dissociation and oxidation capabilities than the Au/TiO2-DP catalyst. The rapid dissociation of hydrogen molecules over the Au/TiO2-PD catalyst accelerated the activation of adsorbed oxygen species and simultaneously promoted the formation of water via hydrogen oxidation. Excessive water accumulation on the catalyst surface occupied the active sites for CO oxidation, thereby imposing an overall inhibitory effect on CO preferential oxidation.