La doping of manganese oxide leads to a dramatically promoted catalytic performance for UV-visible-infrared photothermocatalytic ethyl acetate abatement

La-doped manganese oxide catalysts with nanorod morphology, cryptomelane octahedral molecular sieve structure (OMS-2) and La/Mn atomic ratios of 0.0045, 0.0097, and 0.0459 (denoted as La-OMS-2-A, La-OMS-2-B, and La-OMS-2-C) were synthesized with the reaction among KMnO4, La(NO3)3, and Mn(NO3)2 at 90 degrees C. They were used for photothermocatalytic oxidation of ethyl acetate (typical organic pollutant) merely with UV-vi-sible-infrared (UV-vis-IR) illumination. An appropriate amount of La doping was found to dramatically enhance photothermocatalytic activity and diminish the selectivity of more toxic by-product acetaldehyde. The optimal La-OMS-2-B demonstrated exceptionally large photothermocatalytic activity, low acetaldehyde selectivity, and good catalytic stability. Within initial five minutes, its CO2 formation rate (rCO2) was exceptionally high (1362.0 mu mol g-1 min-1), a 67-fold increase as compared to pure OMS-2, while its acetaldehyde selectivity was very low (1.9%), a 37-fold decrease as compared to pure OMS-2. Even with lambda > 830 nm IR illumination, it still possessed good photothermocatalytic performance. The photothermocatalytic oxidation abided by a light-driven thermo-catalysis mechanism. The dramatic catalytic enhancement by the La-doping arose from a considerable promoted thermocatalytic activity due to the oxygen activity of OMS-2 being substantially improved with La-doping. A photoactivation on La-OMS-2-B, quite unlike photocatalysis on semiconductor photocatalysts, was discovered that further substantially improved catalytic activity and decreased acetaldehyde selectivity due to the oxygen activity of OMS-2 being considerably promoted with UV-vis-IR illumination.

Automated summary

La-doped manganese oxide catalysts with nanorod morphology and cryptomelane octahedral molecular sieve structure showed significantly enhanced photothermocatalytic activity and reduced acetaldehyde selectivity for the oxidation of ethyl acetate. Among the catalysts, La-OMS-2-B exhibited the highest activity and selectivity, even under infrared illumination. The enhancement in catalytic performance was attributed to the promotion of thermocatalytic activity and improved oxygen activity of OMS-2 by La doping.