Heterojunction photocatalyst MnO2-CsSnI3 for highly efficient formaldehyde oxidation at room temperature

The effective removal of the low-concentration formaldehyde (HCHO) in the indoor environment is a critical issue affecting the quality of people’s daily lives. In this study, heterojunction catalysts composed of manganese dioxide (MnO 2 ) and cesium tin iodine (CsSnI 3 ) nanocrystals were first synthesized and successfully used for photocatalytic HCHO degradation. After the full band light irradiation (150 mW/cm 2 ) for 3 h, the concentration of HCHO decreased from 7 ppm to a minimum of 0.03 ppm at room temperature (25 °C, 25 % RH, degradation efficiency reaches up to 99.6 %). Subsequent analysis using electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM) revealed that the MnO 2 -CsSnI 3 heterojunction photocatalyst not only offers a Z-scheme charge-transfer pathway but also promotes the generation of a large number of •O 2 − and •OH. Compared to the single-phase material, the concentration of •O 2 − and •OH has increased by 1.5 times. This MnO 2 -based Z-scheme heterojunction photocatalyst provides a novel strategy for the degradation of low-concentration HCHO in practical indoor environments.