Crystal facet engineering induced robust and sinter-resistant Au/α-MnO2 catalyst for efficient oxidation of propane: indispensable role of oxygen vacancies and Auδ+ species

Abstract

Optimizing the interaction between metal active centers and supports by tuning crystal facets is an effective strategy to improve the activity and stability of catalysts. Herein, α-MnO₂ nanowires with different exposed crystal facets (respectively (310), (110) and (100)) were synthesized via a facile hydrothermal method to promote the activity of an Au/α-MnO₂ catalyst for propane combustion. Results reveal that Au/α-MnO₂-110 exhibits the highest catalytic activity, achieving 90% propane (2500 ppm) conversion at just 216 °C (apparent activation energy as low as 50.2 kJ mol⁻¹). Compared with Au/α-MnO₂-310 and Au/α-MnO₂-100, Au/α-MnO₂-110 with the largest quantity of oxygen vacancies, strong reducibility, and high surface oxygen mobility possesses the best capability for adsorbing and activating oxygen molecules. DFT results reveal that the (110) facet of α-MnO₂ has the lowest formation energy of oxygen vacancies (E_vo(110) = 0.6 eV), suggesting the presence of weak surface Mn–O bonds, facilitating the formation of Au^δ+ species and therefore promoting C–H bond breaking in propane. This work highlights a new strategy for the design of efficient catalysts for stable light alkane low-temperature decomposition by surface exposed facet engineering.