Understanding the Mechanisms of Catalytic Enhancement of La-Sr-Co-Fe-O Perovskite-Type Oxides for Efficient Toluene Combustion

The merits of ABO3-type perovskite oxides as catalysts for volatile organic compounds (VOCs) combustion are that the redox capability of transition metal elements in their lattice structure can be well tailored through a facile doping strategy. In particular, La-Sr-Co-Fe-O perovskite-type oxides possess excellent tunable physicochemical properties, making them an ideal platform for promising prospects in VOCs combustion. This work synthesized a series of La1-xSrxCo1-yFeyO3 (x = 0, 0.3, 0.5, 0.8; y = 0, 0.2, 0.5) perovskites and analyzed their reaction kinetics on toluene combustion. Among all the catalysts, La0.5Sr0.5Co0.8Fe0.2O3-δ (LSCF) showed a remarkable catalytic activity towards the toluene oxidation with T90 of 270 °C at a weight hourly space velocity (WSHV) of 30000 mL·g−1·h−1 and apparent activation energy (Ea) of 44.76 kJ·mol−1 and obtained the superior stability. Based on the characterizations and analysis of in-situ DRIFTS, the outstanding catalytic activity of LSCF perovskite is mainly induced by the improvement of the redox ability, the enriched generation of oxygen vacancies, and the activation of the lattice oxygen species. The catalytic mechanism of toluene conversion over the LSCF perovskite was revealed to be consistent with Mars-van Krevelen (MVK) models. The knowledge obtained in this study provides helpful guidance for designing efficient heterogeneous catalysts of La-Sr-Co-Fe-O perovskite-type oxides toward efficient catalytic combustion for VOCs elimination.