Synthesis of a BiSbS3@BiSbO4/CNH nanocomposite for wastewater treatment and electrochemical application

Abstract

Due to the toxic effects of pentachlorophenol (5-CP), its degradation via photocatalysis is significant because photocatalysis is ecofriendly and cost effective. However, the majority of photocatalysts have a tendency for recombination of fast charge carriers, which limit their efficacy. To combat this issue, a carbon nanohorn (CNH)-modified BiSbS₃/BiSbO₄ (BiSbS₃@BiSbO₄/CNH) nanocomposite was synthesized by hydrothermal method to degrade the endocrine disrupting agent 5-CP. Structural composition, morphology, porosity as well as optical characteristics of the BiSbS₃@BiSbO₄/CNH nanocomposite (B@B/CNH) were analyzed via different characterization techniques. B@B/CNH was observed to have a low band gap of 2.64 eV compared to its counterparts BiSbS₃ (BSbS), BiSbO₄ (BSbO), and BSbO/CNH, which indicated its efficient photocatalytic potential. Various reaction factors like pH, B@B/CNH dosage, 5-CP concentration, and time were optimized, and B@B/CNH exhibited 93% efficiency at pH 6 and a dosage of 0.1 g L⁻¹ for the degradation of 10 ppm 5-CP under visible light irradiation for 140 minutes, exceeding that of their counterparts BSbO/CNH (84%), BSbS (82%) and BSbO (81%). The kinetic study showed that the degradation of 5-CP followed the pseudo-first-order model with R² = 0.975. A scavenger study was performed to gain insights into the mechanistic path, which indicated that all the charge carriers, like holes, electrons, oxide radicals and hydroxyl radicals, are involved in the photodegradation, but among them, oxide radicals played the most prominent role during the photocatalysis process. Further, the effect of other phenolic pollutants on the degradation of 5-CP was evaluated, which indicated that B@B/CNH can be employed for the eradication of other pollutants along with 5-CP. Additionally, the degradation behavior of 5-CP was evaluated by density functional theory (DFT), which was in line with the results obtained from the scavenger study. Additionally, an electrochemical study was performed for B@B/CNH to understand its electrochemical performance for supercapacitor applications.