Ultra-small CeO2 nanoparticles supported on SiO2 for indoor formaldehyde oxidation at low temperature

Abstract

Formaldehyde (HCHO) elimination is very important for air cleaning in indoor spaces because it is a human carcinogen. HCHO oxidation over an oxide catalyst is more practical for large-scale applications than using a noble catalyst, but the activity is a big challenge at low temperature. One strategy to improve the activity is to fabricate ultra-small oxide nanocrystals that exhibit a size effect. In this work, ceria nanoparticles with a size of around 2.5 nm were synthesized. The nanoparticles are some of the smallest ceria nanocrystals that have been developed. Compared with ceria aggregates and bulk materials, the ultra-small ceria nanoparticles exhibited excellent performance for HCHO elimination, where HCHO was fully oxidized at 523 K under dry and moist conditions at a high gas hourly space velocity. The superior performance was assigned to the remarkable oxygen vacancies in the ultra-small ceria nanoparticles that have the ability to activate O₂. This work demonstrates the importance of ceria size control for achieving abundant oxygen vacancies for low temperature HCHO oxidation, which might also be applicable to other catalysts for oxidation reactions.