Preparation of Perovskite Cs3Bi2Br9/Biochar Composites and Their Photocatalytic Properties

Halide perovskites have many advantages in environmental remediation. The photocatalytic performance of halide perovskites is often hindered by low specific surface area and rapid photogenerated carrier recombination. The aim of this work is to prepare a green, novel photocatalyst in the form of biochar-anchored Cs3Bi2Br9 perovskite composites. The rose-petal-derived biomass carbon (RC) provides adsorption sites and high electrical conductivity, while the perovskite Cs3Bi2Br9 can efficiently capture visible right and degrade pollutants, and the reciprocal effect can enhance the photocatalytic efficiency of the composite. The results of scanning electron microscopy (SEM) showed the Cs3Bi2Br9 particles were loaded on the surface of RC. Compared with bare Cs3Bi2Br9, Cs3Bi2Br9/RC composite has a more perfect structure, higher specific surface area, enhanced ability to absorb visible light, and reduced bandgap value. As visible-light-driven photocatalysts, the prepared Cs3Bi2Br9/RC composites can enhance the removal efficiency of Rhodamine B. The Cs3Bi2Br9/RC–0.2 composite displays the highest degradation efficiencies for RhB (10 mg/L), reaching 98% within 60 min. And the rate constant (k) is 1.9 times that of bare Cs3Bi2Br9. The results of electrochemical impedance spectroscopy (EIS) show that the interaction between RC and Cs3Bi2Br9 speeds up charge carrier separation and transfer. During photocatalytic process, holes (h+) and superoxide radicals (·O2−) played major roles. The composites also showed excellent stability. It is meaningful to deal with a large number of withered rose petals to make them high-value products. This work not only provides a guideline for the construction of perovskite composites materials but also shows the promising prospects of biochar composites in deep treatment for contaminated water.