Hierarchically nanostructured Ag/ZnO/nBC for VOC photocatalytic degradation: Dynamic adsorption and enhanced charge transfer

The adsorption-photodegradation strategy can achieve continuous enrichment and efficient oxidation of volatile organic compounds (VOCs), but it requires a trade-off among adsorption, mass transfer, and charge transfer in this dynamic process. Therefore, the construction of an effective and stable catalytic system remains an immense challenge. Here, we report a strategy for constructing a hierarchically structured photocatalyst for efficiently degrading VOCs by assembling nanobiochar (nBC, ∼ 6.25 µm), the active center of ZnO (∼ 460 nm), and plasmonic-Ag nanoparticles (Ag NPs, ∼ 10 nm). Benefiting from its abundant surface functional groups (–OH, –CO, and –CO) and hierarchical structure-induced mesopores and macropores, VOCs can be quickly captured and dynamically diffused. Furthermore, Ag NPs build a charge transfer bridge and accumulate electrons to nBC from both the photogenerated electrons that are induced by ZnO and hot electrons from the local surface plasmon resonance (LSPR) effect of Ag NPs. Afterward, a desirable spatial separation of charge carriers and visible-light response can be achieved. Therefore, Ag/ZnO/nBC maximizes the reactive oxygen species (e.g., ·OH and ·O2−) and shows a 7.8 times higher degradation rate of formaldehyde than ZnO, and it also displays universality and stability with high photocatalytic efficiency. The photocatalytic performance was comprehensively determined based on the relative humidity, initial concentration, catalyst dose, and mass ratio of Ag NPs. This facile and universal strategy for architecting hierarchically structured photocatalysts provides an approach for enhancing photocatalytic performance for VOC degradation and environmental pollution treatment.