Ultralow Doping of Mn Species into Pt Catalyst Enhances the CO Oxidation Performance in the Presence of H<sub>2</sub>O and SO<sub>2</sub>
Xiaolong Liu, Yang Zou, Xue Li, Tieyao Xu, Wanglai Cen, Bin Li, Tingyu Zhu
Abstract
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 H 2 O and SO 2 . 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 H 2 O 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 SO 2 adsorption energy calculations demonstrated that SO 2 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 revealed that the introduction of SO 2 onto Pt–0.5Mn/Ti showed little change for CO adsorption on different Pt species, while Pt/Ti showed an apparent decrease of Pt 0 –CO. 18 O isotopic experiments in the presence of H 2 18 O and SO 2 were systematically designed to accurately quantify the CO 2 composition including C 16 O 16 O, C 16 O 18 O, and C 18 O 18 O. Accordingly, the reaction mechanism for Pt–0.5Mn/Ti catalyzed CO oxidation consisting of four pathways was proposed.