Effect of Crystal Structure and Tunnel K<sup>+</sup> on the Sintering Resistance of Rod-like MnO<sub>2</sub> Catalysts for Catalytic Combustion of Toluene
Chi Zhang, Ye Feng, Shengwei Tang, Yunfa Chen, Wenxiang Tang
Abstract
Rational design of the catalyst structure was urgently required to break the activity-stability trade-off, but it remains a daunting challenge. Herein, rod-like MnO 2 polymorphs with different crystal structures (α-, β-, and γ-MnO 2 ) were synthesized to reveal the structure–performance relationship. A fresh γ-MnO 2 catalyst exhibits better catalytic activity than α- and β-MnO 2 catalysts, while the decay of T 10 after the thermal aging operation is the most severe due to its poor structural stability. Particle rearrangement during the phase transformation would accelerate the sintering of MnO 2, resulting in structural collapse, reduction in specific surface area and amount of active oxygen species, and weakened reducibility, thereby significantly affecting the catalytic performance. More importantly, the crucial role of K + ions in the α-MnO 2 tunnel for enhancing catalytic activity and stabilizing material structure was elucidated by a series of characterization and DFT calculation findings.