Effects of A-site cations (Sm, Y, Gd) on methanol oxidation over AMn2O5 mullite catalysts

• AMO catalysts doped with different rare-earth elements (Sm, Y, Gd) at the A-site were synthesized via a facile hydrothermal method. • GMO exhibited the best catalytic performance with methanol conversion outperforming 98 % in 150-450 °C. • GMO catalyst exhibited a higher Mn 4+ /Mn 3+ ratio (0.33), greater O ads /O lat ratio (1.07), and enhanced surface oxygen mobility. • In situ DRIFTS results strongly suggested that formate species were likely the key intermediates in methanol oxidation pathway over GMO catalyst. Manganese-based mullite-type oxides are widely used in VOCs oxidation, and their catalytic performance can be effectively regulated by modifying the A-site elements. Here, a series of Mn-based mullite catalysts (AMn 2 O 5 , A = Sm, Y, Gd) with different rare-earth elements at the A-site were synthesized via hydrothermal method and applied for methanol catalytic oxidation. The GdMn 2 O 5 catalyst demonstrated optimal low-temperature activity, achieving 98 % CH 3 OH conversion at 150 °C. Comprehensive characterization results revealed that the largest specific surface area (40.08 m 2 /g), highest Mn 4+ /Mn 3+ ratio (0.33), maximum O ads /O lat ratio (1.07), highest concentration of oxygen vacancy and enhanced surface oxygen mobility collectively contributed to the superior catalytic performance of GdMn 2 O 5 . In situ DRIFTS was employed to investigate the intermediate species and catalytic mechanism of GdMn 2 O 5 during methanol oxidation. This study provides an important theoretical basis for the rational design of AMn 2 O 5 catalysts and the catalytic oxidation of methanol by fully leveraging the rare earth cation effect, modification, and optimization.