Constructing γ-MnO2 with abundant oxygen vacancies by a chelating agent-assistant strategy to achieve high-efficient conversion of NO to NO2

Abstract

To date, the exploitation of non-noble materials of high-efficiency and low-temperature conversion of NO to NO2 still existed as a challenging task due to high cost of current Pt-based commercial catalysts. Herein, we employed a chelating agent-assistant strategy to regulate the content of oxygen vacancy over γ-MnO2 catalysts, which were further used for NO oxidation. Benefiting from the structure-directing effect of tartaric acid, the resultant locus-shaped γ-MnO2 catalyst with abundant oxygen vacancies showed a remarkable low-temperature catalytic activity (T50 and T92 of 127 and 225 °C; respectively), which was superior to unmodified γ-MnO2 sample (T50 at 189 °C) and those recently reported good-performing NO oxidation catalysts. An array of characterization results revealed that an extended capping by means of chelating agents could effectively weaken the MnO bond strength and promote the formation of oxygen vacancy (OVs), thus tremendously increase the amount of surface-active oxygen species. Moreover, theoretical calculation demonstrated that an enriched OVs concentration could enhance the reactivity of surface lattice oxygen by reducing the formation energy of OVs, further accelerating reaction rate of the adsorption/activation of O2 molecules and thus bringing about an outstanding low-temperature catalytic activity. This study highlighted the potential of chelating agents in the design of high-efficient catalysts for environmental remediation and beyond.