Facet selectively exposed α-MnO2 for complete photocatalytic oxidation of carcinogenic HCHO at ambient temperature

Formaldehyde (HCHO) causes increasing concerns due to its ubiquitously found in the indoor environment and being irritative and carcinogenic to humans. Therefore, the complete removal of HCHO at room temperature is meaningful. Crystal facet engineering has appeared as a significant strategy for designing efficient catalysts. It is an effective way to improve the catalytic activity by selectively exposing the highly reactive crystal facets. Herein, the {1 0 0}, {1 1 0}, and {3 1 0} facets in alpha-MnO2 were selectively exposed, and the differences in the properties and photocatalytic activity of crystal facets have been carefully compared. Specifically, alpha-MnO2 with exposed {3 1 0} facets exhibited superior photocatalytic activity, achieving 100% conversion of carcinogenic airborne HCHO under the solar-light irradiation and even 78% removal efficiency under visible light. Interestingly, it is found that the high activity of {310} facet with solar-light irradiation is consistent with the photo catalysis mechanism, rather than solar-light-driven thermocatalysis mechanism. Furthermore, it is confirmed that the {3 1 0} facet can not only promote the effective separation of electron and hole, but also benefit the activation of O-2, which leads to substantially improved photocatalytic activity. This is the first report on engineering surface structures and facets control in the preparation of alpha-MnO2 as highly efficient photocatalysts.

Automated summary

This study compared the properties and photocatalytic activity of different crystal facets of α-MnO2 by selectively exposing them. The α-MnO2 with exposed {3 1 0} facets exhibited superior photocatalytic activity under solar-light irradiation and visible light.