Selectively Etching Lanthanum to Engineer Surface Cobalt-Enriched LaCoO3 Perovskite Catalysts for Toluene Combustion

As appropriate alternatives to precious metals in volatile organic compound (VOC) combustion, La-based perovskites have attracted increasing attention due to their tunable structure and sintering-resistance capacity. Herein, chemically tailored surface Co-enriched LaCoO3 perovskite oxides (LCO) with abundant surface defects were successfully constructed via a facile selective acid-etching method, in which lanthanum located at the A-site was preferentially dissolved and exsolved cobalt opportunely dispersed on the surface of the perovskite. The unique LCO catalysts could enhance the electron transfer and facilitate the activation of oxygen molecules through the interface Co2+/Co3+ redox cycles. Among all as-synthesized LCO catalysts, the LCO-20 sample (LaCoO3 treated with 1 M HNO3 for 20 min) revealed the optimum catalytic performance (T-50 and T-90 of 184 and 206 degrees C at a space velocity of 15 000 mL/(g h) with 1000 ppm toluene, respectively), stability, and durability (5 vol % water). The excellent activity of LCO-20 might be mainly ascribed to the accelerated activation and circulation of the oxygen species initiated by the surface defects and Co2+/Co3+ redox cycles.