Engineering Oxygen Vacancies on Ceria via Vanadium Oxide Dispersion for Selective Photocatalytic Cleavage of Lignin C-C Bonds

Abstract

Lignin, the most abundant natural aromatic polymer on Earth, offers a promising feedstock for the production of value-added aromatic products through selective C-C bond cleavage. However, achieving both high product yield and selectivity under mild conditions, such as under visible-light irradiation, remains a significant challenge. In this study, we address this issue by employing ceria (CeO2) as a support to precisely engineer the dispersion of vanadium oxide through two distinct catalyst pretreatment methods: impregnation–calcination (Im-V/CeO2) and physical mixing–calcination (Pm-V/CeO2). The results demonstrate that the Im-V/CeO2 catalyst exhibits superior performance, converting 1,2-diphenylethanol to benzaldehyde with an impressive 89% yield and 98% selectivity, while CeO2 alone yields 52% and Pm-V/CeO2 yields 45%. This enhanced performance of Im-V/CeO2 is attributed to the introduction of low-polymerized vanadium oxide (VOx) species. Unlike highly polymeric V2O5 crystals, these species facilitate the separation of photogenerated electron-hole pairs and reduce charge transfer resistance, thereby improving photocatalytic efficiency. Additionally, the polar nature of VOx species enhances the activation of lattice oxygen, creating more sites for oxygen adsorption and activation. In-depth mechanistic studies reveal that superoxide radicals play a dominant role in the C-C bond cleavage process. This innovative strategy for achieving high-efficiency photocatalytic C-C bond cleavage through the controlled dispersion of vanadium oxide on a cerium oxide support offers valuable insights for the sustainable valorization of lignin.