Enhanced visible-light degradation performance toward gaseous formaldehyde using oxygen vacancy-rich TiO2-x/TiO2 supported by natural diatomite

Abstract

Natural mineral-based composites with outstanding photocatalytic performance have attracted much attention because of their great potential applications in environmental remediation. Herein, we report a natural diatomite supported oxygen vacancy-rich TiO2-x-TiO2 homojunction (TOV-TD composite) photocatalyst for indoor gaseous formaldehyde (HCHO) purification. The designed composite exhibits superior sustainability and mineralization efficiency of HCHO under visible light illumination, which is attributed to the constructed high-efficient adsorption-photocatalysis collaborative system composed of TiO2, TiO2-x and diatomite. In addition, according to the variation of the CO2 concentration in real time, the calculated HCHO mineralization rate constant of TOV-TD-1:3 composite (optimal sample) is up to around 4.42 times that of bare TiO2-x (TOV) and 1.74 times that of TiO2-x-TiO2 (TOV-T) composite, respectively. It is indicated that the introduction of the natural diatomite significantly promotes the content of oxygen vacancies in the composite and provides more adsorption-photocatalysis active centers. Moreover, the hydroxyl radicals (•OH) are proved to be the major active species for HCHO mineralization. This work provides a new composite for constructing adsorption-photocatalysis systems with enhanced visible-light properties for indoor HCHO removal.