g-C3N4@CPP/BiOClBr-OV biomimetic fractal heterojunction synergistically enhance carrier dynamics for boosted CO2 photoreduction activity.

This study employed carbonized pomelo peel (CPP), a waste biomass material, to successfully craft a CN@CPP/BOCB-OV ternary heterojunction abundant in N/O vacancy defects. Compared with the pristine single material the photocatalytic activity of the heterojunction system was increased by 55.0 times and 35.6 times respectively. Importantly, the heterojunction demonstrated the ability to reduce CO 2 even under infrared light excitation, a crucial step for cascade sunlight utilization. Through a series of characterizations, experiments and DFT calculations, we revealed the coupling effect of CPP as a multi-site cooperative center with the double defects and built-in electric field in the heterojunction system. Subsequently, the photocatalytic activity enhancement mechanism has been elucidated. This work combines the strategies of waste biomass utilization, heterostructure construction and defect engineering, achieves the multi-site synergistic enhancement for CO 2 photoreduction, and offers a promising approach in designing efficient heterostructure photocatalysts. [Display omitted] • The synthesized heterojunction exhibits the capacity to reduce CO 2 under infrared light irradiation. • The g-C 3 N 4 @CPP/BiOClBr-OV shows high yield and selectivity of CO production in photocatalytic CO 2 reduction. • The introduction of CPP enhances the interface electric field within the initial heterojunction. • g-C 3 N 4 @CPP/BiOClBr-OV achieves the three-in-one combination of photothermal sites, electron concentration sites, and CO 2 adsorption active sites. • The electron transfer mechanism at the heterojunction interface has been elucidated. In recent years, there has been significant interest in generating high-value solar fuels via the photocatalytic reduction of CO 2. Nonetheless, its large-scale application is impeded by low energy utilization efficiency and limited photocatalytic activity. This study employed carbonized pomelo peel (CPP), a waste biomass material, to successfully craft a CN@CPP/BOCB-OV ternary heterojunction abundant in N/O vacancy defects through secondary calcination and in-situ growth. The construction of the heterojunction and the emergence of defect-induced donor energy levels create a built-in interface electric field (IEF) and an interfacial electron transmission channel respectively, fortifying the separation and transport of photogenerated electrons. Crucially, following the incorporation of CPP, its distinctive 3D porous and heterojunction bionic flower structures expand the spectral absorption range. Acting as a superior electron acceptor, CPP reinforces the IEF, notably boosting carrier transport efficiency. Simultaneously, it operates as a hub for photothermal synergy and CO 2 adsorption activation, achieving multi-site synergistic enhancement of photoreduction CO 2 activity. Hence, the CN@CPP/BOCB-OV heterojunction demonstrates a substantial quantitative enhancement in CO 2 photoreduction activity. Remarkably, it exhibits the capability to catalyze CO 2 reduction even under infrared light excitation, which is of great significance for the cascade utilization of solar energy. Furthermore, employing DFT calculations, we elucidate the electron transfer mechanism at the heterojunction interface and outline potential pathways for photocatalytic CO 2 reduction. The combination of waste biomass utilization, heterostructure construction and defect engineering provides a promising strategy for developing efficient heterostructure photocatalysts. [ABSTRACT FROM AUTHOR]