Construction of S-scheme Zn0.2Cd0.8S/biochar aerogel architectures for boosting photocatalytic hydrogen production under sunlight irradiation

Developing highly efficient, stable, and full-spectrum responsive non-precious photocatalyst is high desirable due to photocatalytic water splitting is a green technology for hydrogen evolution. In this work, a type of biochar-based composite photocatalysts is fabricated by a facile green microwave-assisted aqueous chemical deposition, which consists of monodispersed Zn0.2Cd0.8S nanoparticles (ZCS NPs) uniformly decorating on three-dimensional (3D) biochar aerogel (BA) derived from the biomass castoff tangerine peel. As-engineered ZCS/BA composite photocatalysts exhibit significantly strengthened photocatalytic activities under solar irradiation, in which the optimal 0.4ZCS/BA sample (0.4 represents the molar of ZCS) achieves the average photocatalytic hydrogen production efficiency of 10.52 mmol g−1∙h−1, being 24.5 folds higher than that of monolithic ZCS alloy. The boosted photocatalytic hydrogen evolution is ascribed to the synergistic effect on the heteroarchitecture with the closely interfacial interaction, which is beneficial for increasing the broad-spectrum sunlight absorption, promoting the photo-induced charge carriers separation efficiency, and accelerating the chemical reaction dynamic rate by the photothermal effect. The step-scheme (S-scheme) electron transfer mechanism for binary ZCS/BA heterojunction is proposed based on the experimental data and density functional theory (DFT) calculation. The study guides a practical approach to developing biochar-based composites for highly efficient utilization of agricultural biomass resources as well as conversion of solar energy to fuel in photocatalysis.