Catalytic Performance and in Situ Surface Chemistry of Pure alpha-MnO2 Nanorods in Selective Reduction of NO and N2O with CO

Search of catalysts made of nonprecious metal for reduction of nitric oxide is important for having a sustainable environment. Catalytic performances of alpha-MnO2 nanorods in reduction of nitric oxide and nitrous oxide by carbon monoxide were investigated. Surface chemistry of alpha-MnO2 catalyst during catalysis was tracked with ambient pressure X-ray photoelectron spectroscopy. Correlation between catalytic performance and the corresponding in situ surface chemistry during catalysis revealed that Mn3+ ions and oxygen vacancies are active catalytic sites. Bulk phase of alpha-MnO2 nanorods below the catalyst surface is restructured to Mn3O4 in catalysis. Kinetics studies suggested that the reduction of nitric oxide with CO is performed through the formation of the intermediate N2O with a followed dissociation to N-2. This study suggested restructuring of transition metal oxides can tune catalytic performance and even develop catalysts.