The effect of hydrogen reduction of alpha-MnO2 on formaldehyde oxidation: The roles of oxygen vacancies

A series of alpha-MnO2 catalysts with various Mn valence states were treated by hydrogen reduction for dif-ferent periods of time. Their catalytic capacity for formaldehyde (HCHO) oxidation was evaluated. The results indicated that hydrogen reduction dramatically improves the catalytic performance of alpha-MnO2 in HCHO oxidation. The alpha-MnO2 sample reduced by hydrogen for 2 h possessed superior activity and could completely oxidize 150 ppm HCHO to CO2 and H2O at 70 degrees C. Multiple characterization results illustrated that hydrogen reduction contributed to the production of more oxygen vacancies. The oxygen vacancies on the catalyst surface enhanced the adsorption, activation and mobility of O 2 molecules, and thereby en-hanced HCHO catalytic oxidation. This study provides novel insight into the design of outstanding MnOx catalysts for HCHO oxidation at low temperature.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.