Photocatalytic mineralization of indoor VOC mixtures over unique ternary TiO2/C/MnO2 with high adsorption selectivity

Formaldehyde (CH2O) and toluene (C7H8) are typical indoor air pollutants that have high harm to people's health. Photocatalytic oxidation is a feasible approach, but still remains the problem of incomplete degradation to form refractory intermediates and uncertainty of interaction between multivariant components. This paper used natural proteins from waste shell as the carbon source and template to synthesize the ternary TiO2/C/MnO2 photocatalysts. It exhibited high adsorption selectivity and excellent photocatalytic performance for CH2O and C7H8 mixture mineralization under visible light irradiation. The optimal candidate achieved near completely mineralization within 60 min in the simulated indoor environment and exhibited remarkable stability after 5 cycles. Large amounts of oxygen vacancies, lattice distortions of TiO2, and tailored bandgap structure contributed to these excellent behaviors. Besides, carbon existence as an electron transfer channel dropped the interfacial charge-transfer resistance, thus prolonging the lifetime of charge carriers and making them rapidly go through the surface photo-oxidation reactions. In-situ DRIFTs results indicated that CH2O and C7H8 mixtures possessed the same reaction pathway and rate-determining step with single component. Above all, this paper offered a facile, sustainable, and green approach to synthesize efficient photocatalysts for treating indoor CH2O/C7H8 pollution with visible light irradiation.