Enhancement of toluene removal over α@δ-MnO2 composites prepared via one-pot by modifying the molar ratio of KMnO4 to MnSO4·H2O.

[Display omitted] • α@δ MnO 2 with α and δ phase are in situ synthesized via one-pot. • α@δ MnO 2 exhibits better catalytic performance compared to pure α-MnO 2 and δ-MnO 2. • α@δ-2 with the closest two-phase proportion owns the best catalytic activity. • α@δ-2 has excellent physicochemical properties compared to other prepared catalysts. The construction of composite crystal structure is an effective strategy for developing enhanced functionality and can generally be constructed via two steps. Herein, a series of α@δ-MnO 2 catalysts with different α/δ phase ratios are one-pot synthesized using a hydrothermal method; their molar ratio of KMnO 4 to MnSO 4 ·H 2 O was accurately controlled from 2.9 to 3.7. The catalytic results show that all α@δ-MnO 2 catalysts exhibit significantly better catalytic performance in oxidizing toluene than single α-MnO 2 and δ-MnO 2 due to a synergistic effect, in which α@δ-2 with the closest two-phase proportion has the highest activity (T 90 = 238 °C under a WHSV of 60,000 mL·g−1·h−1). Various characterization results indicate that α@δ-2 has the largest specific surface area, highest defects, oxygen vacancies, and best low-temperature reducibility among α-MnO 2 , δ-MnO 2 , and α@δ-2. Also, the possible reaction pathway for oxidizing toluene over the prepared catalysts is speculated using both TD/GC–MS and in-situ DRIFTS experiments. [ABSTRACT FROM AUTHOR]