Ultralow Doping of Mn Species into Pt Catalyst Enhances the CO Oxidation Performance in the Presence of H₂O and SO₂

Bimetallic catalysts Pt-M/Ti were prepared by introducing various dopants (M = Mn, Fe, Co, Cu, Ce, Mo) into Pt/Ti with ultralow loadings (0.5 wt % M) and compared in CO oxidation in the presence of H2O and SO2. Among these catalysts, Pt-0.5Mn/Ti contributed the highest oxidation efficiency and strongest sulfur resistance. Further improvement of Mn contents led to the decrease of CO conversion. It was indicated that the introduction of appropriate Mn species enhanced the active oxygen supplying ability of the catalyst, thus improving the reaction activity. The CO oxidation performance of the catalyst was improved through the reaction between *OH from H2O dissociation and CO. The deposition of S on the Pt-0.5Mn/Ti surface did not increase with time extension. Theoretical calculation results revealed that cleavage of S-O-Mn species could be facilitated by Pt, and the SO2 adsorption energy calculations demonstrated that SO2 was more easily adsorbed on Pt/Ti than Pt-0.5Mn/Ti, which was very consistent with its sulfur resistance. In situ DRIFT studies at 260 C-degrees revealed that the introduction of SO2 onto Pt-0.5Mn/Ti showed little change for CO adsorption on different Pt species, while Pt/Ti showed an apparent decrease of Pt0-CO. 18O isotopic experiments in the presence of H-2 18O and SO2 were systematically designed to accurately quantify the CO2 composition including (COO)-O-16-O-16, (COO)-O-16-O-18, and (COO)-O-18-O-18. Accordingly, the reaction mechanism for Pt-0.5Mn/Ti catalyzed CO oxidation consisting of four pathways was proposed.