Rare Earth Dopants Enhance Thermocatalytic Activity of Manganese Oxides on Corrugated Silica Carriers for Formaldehyde Degradation

Abstract

The development of high efficiency thermocatalysts remains a great challenge for gaseous formaldehyde elimination. Herein, rare earth‐doped manganese dioxide (RE‐MnO2) particles with sizes of approximately 200 nm were deposited on corrugated silica carrier (CSC) by using cerium or samarium as dopants. One part of rare earth ions in RE‐MnO2/CSC were substituted for the manganese ions in α‐MnO2, and the other part existed in the form of cerium oxide or samarium oxide. RE‐MnO2/CSC exhibited better thermocatalytic activity than MnO2/CSC. The formaldehyde removal efficiency over RE‐MnO2/CSC reached nearly 100 % even after cycle tests of 5 times. Both the cerium and samarium doping accelerated HCHO oxidation via increasing lattice oxygen and Mn4+ amounts, improving low‐temperature redox properties, and reducing apparent activation energy. Notably, the RE oxides in the catalysts played different roles in HCHO degradation. Samarium oxide did not possess thermocatalytic activity, while cerium oxide in RE‐MnO2/CSC participated directly in the formaldehyde degradation via the CeO2↔Ce2O3 redox reaction and facilitated the oxidation of Mn2O3 into MnO2. This work revealed the effect mechanisms of RE doping and RE oxide on the enhanced thermocatalytic activity, and provided a novel viewpoint to develop RE‐doped catalysts for formaldehyde removal.