Identification of active sites for preferential oxidation of CO over Ru/TiO2 catalysts via tuning metal–support interaction

Preferential oxidation of CO (CO-PROX) is promising to purify H2 resources for proton-exchange membrane fuel cells with the challenges of identifying active sites and developing efficient catalysts. Herein, we report the high CO-PROX performance of Ru/TiO2 catalysts prepared by chemical-reduction method. The kinetic results reveal that the CO-PROX mechanism over the Ru/TiO2 catalysts follows the Langmuir-Hinshelwood model. We discover that Ruδ+ sites are more active for O2 activation and CO oxidation, while Ru0 sites prefer CO methanation in CO-PROX. The enhanced metal–support interaction (MSI) induces the formation of flat Ru nanoparticles, thereby increasing the number of interfacial Ruδ+ sites. Especially, compared with the conventional catalyst prepared by conventional wetness impregnation method, the as-synthesized RuTi-CR-R200 catalyst with strengthened MSI exhibits about 27 and 13 times higher reaction rate and intrinsic activity, respectively, for CO-PROX. To the best of our knowledge, our catalyst surpasses the catalytic performance of the reported Ru-based catalysts, and achieves 100% CO conversion in the wide temperature range of 90–150 °C, as well as high stability.