Biochar (BC) is a carbon-rich material produced from pyrolysis of biomass. In addition to its low toxicity, environmental compatibility, and low cost, BC has the desired advantages of well-developed mesoporous structure and abundant surface functional groups. In recent years, BC-based photocatalysts (BCPs) have played a significant role in many environmental fields. In this paper, we highlight the current progress and several exciting results of BCPs by focusing on their synthesis, characterization, mechanisms, and applications in wastewater treatment. Details on various preparation methods include sol–gel, hydrothermal/solvothermal, ultrasound, calcination, and in situ methods are summarized and discussed. The underlying mechanisms and the applications of BCPs for different semiconductors are reviewed. Furthermore, some future trends and potentials are outlined.

Through cyclic voltammetry (CV) curve, electron spin resonance spectroscopy (ESR) characterization and free radical competitive trapping experiment, an analysis was performed on the mechanism of persulfate (PDS) electro-synthesis by sulfate at boron-doped diamond (BDD) anode.

HNO3-modified activated carbon was used to make electrodes for single-pass capacitive deionization for removing F- from drinking water. The optimal operating conditions for F¯ removal were studied, and the F¯ removal performance, cycle stability, and charge efficiency of the electrode were investigated. Based on these results, an optimization scheme was proposed for practical applications. After HNO3 modification, the proportion of micropores, specific surface area, and number of oxygen-containing functional groups on the activated-carbon surface increased, resulting in a significant increase in the specific capacitance of the electrode. Under optimal operating conditions, the adsorption capacity of the modified electrode was 13% higher than that of the unmodified electrode, while the charge efficiency increased by 25% and reached a peak value after about 1,100 s. The HNO3-modified electrode had good cycle stability, and maintained 83% of the original adsorption capacity after 5 cycles. Optimizing the adsorption time (1,500 s) and desorption time (900 s), 80% of the specific adsorption capacity was maintained after 5 cycles. In addition, the cycle time was reduced by 32%, and the utilization rate of electric-double-layer adsorption sites was optimized, resulting in a reduction in the energy consumption per unit F¯ removal.

Low-concentration antibiotic wastewater is difficult to treat rapidly using conventional photocatalysts. For this reason, this paper simplified the traditional sol–gel method to prepare Fe³⁺-TiO₂/AC composites and characterized the properties of the composites using FT-IR, XRD, SEM, BET, and TEM. The results demonstrated that iron was uniformly dispersed on the surface of the composites, and the activated carbon (AC) was successfully loaded with iron-doped titanium dioxide. Afterward, ciprofloxacin (CIP) was used as the target degradant, and the effects of different activated carbon loadings, iron-doping, pH, initial concentrations, and UV light intensities on the removal of ciprofloxacin were investigated. The repetitive photocatalytic stability of the composites was studied, and the reaction mechanism was explored by using free radical quenching experiments. The results demonstrated that while iron doping reduced the rate at which photogenerated electrons and holes could combine, loading AC increased the usage efficiency of the composites’ adsorption and catalytic active sites. According to the parameter tests, the circumstances that led to the highest CIP degradation efficiency (94.59%) were as follows: 10 mg/L CIP, 0.5 g/L 0.2%Fe³⁺-TiO₂/20%AC, and solution pH of 7 under 40 min of UV light irradiation. In addition, the Fe³⁺-TiO₂/AC composite material has excellent cyclic stability, the degradation rate of CIP can still reach 87.73% at 60 min after four repeated degradation tests under the same conditions. The applicability of this method could be expanded to the treatment of various industrial organic pollutants in water.

High-quality, all-inorganic CsPbBr₃/Cs₄PbBr₆ composite perovskite nanocrystals (NCs) were obtained with all-solution-processing at room temperature, and a photodetector (PD) with high detectivity was realized based on CsPbBr₃/Cs₄PbBr₆ NCs. The detectivity (D*) of the proposed PD is 4.24 × 10¹² Jones under 532 nm illumination, which is among the highest levels for PDs based on all-inorganic perovskite NCs. In addition, a high linear dynamic range (LDR) of 115 dB under 1 V bias was also realized. Furthermore, the underlying mechanism for the enhanced performance of the proposed PD was discussed. Our work might promote the preparation of high-performance PDs based on dual-phase all-inorganic perovskite nanocrystals.