Insight into the roles of superoxide-type (Mn(-O-)2Mn), bridge-type (Mn-O-Mn), and terminal-type (MnO) oxygen species on MnO2 of different crystal structures in CO oxidation using operando TPR-DRIFTS-MS

MnO 2 is a promising catalyst due to its abundant metal valence and good redox ability. Different crystal phases of MnO 2 have different oxygen species, but the relationship between their catalytic activity and crystal structures is unclear. In this study, four MnO 2 catalysts with crystal structures ( α -, β -, γ -, and δ -MnO 2 ) were selected to unveil the roles of terminal-type (Mn O), superoxide-type Mn(-O-) 2 Mn, and bridge-type (Mn-O-Mn) oxygen species in CO oxidation . γ -MnO 2 has the best CO oxidation performance. Density functional theory calculation results show that Mn O on γ- MnO 2 can adsorb CO easier than other two types of oxygen species. Operando TPR-DRIFTS-MS results show that Mn O on the surface of γ- MnO 2 can react with CO to form terminal-type oxygen vacancies (M 2+ =□ 2– ) at low temperatures. Meanwhiles, Mn(-□-)(-O-)Mn and Mn-□-Mn can dissociate O 2 to form Mn O under certain conditions to promote CO oxidation. MnO 2 catalysts with more Mn O oxygen species are of great significance for CO oxidation at a low temperature.