Visible-light-activated TiO2 photocatalysis regionally modified by SiO2 for lignin depolymerization

Abstract

In the high-value utilization of lignin, the photocatalytic technology to break β-O-4 linkages is a green strategy to obtain small molecular oxygenated polycyclic aromatic hydrocarbons. TiO2 is regarded as a promising photocatalyst for breaking β-O-4 linkages, whose band gap width is up to 3.2 eV, unfortunately inhibiting the activity in the visible region. Surface engineering is an effective strategy that can shorten the bandgap width of TiO2 and modulate its photocatalytic performance via impurity-free introduction of oxygen defect sites. Herein, we report a TiO2 micrometer spheres with surface oxygen-deficient structures obtained directly by hydrogenated TiO2, whose regionalized surface is modified by amorphous SiO2. The oxygen vacancies prolong the carrier separation time on the TiO2 surface and transfer electrons through Ti–O–Si bonds to the lignin models bound to Si–OH thereby generating radicals. The surface modification of SiO2 not only enhances the adsorption capacity to the lignin models but also achieves the effective utilization of PV illumination per unit area by refracting the incident light. Simultaneously, the catalyst performance is reasonably optimized by the regional distribution of SiO2 when combined with lignin models in a point-to-point manner. The TiO2 photocatalysis regionally modified by SiO2 is designed as an ingenious model for the direct photocatalytic oxidation of target through a directional integrated avenue.