Effect of Crystal Structure and Tunnel K⁺ on the Sintering Resistance of Rod-like MnO₂ Catalysts for Catalytic Combustion of Toluene

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 MnO₂ polymorphs with different crystal structures (α-, β-, and γ-MnO₂) were synthesized to reveal the structure-performance relationship. A fresh γ-MnO₂ catalyst exhibits better catalytic activity than α- and β-MnO₂ catalysts, while the decay of <i>T</i>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 MnO₂, 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-MnO₂ tunnel for enhancing catalytic activity and stabilizing material structure was elucidated by a series of characterization and DFT calculation findings.