Integrating BiOI/g-C3N4/Bi2WO6 Derived Dual S-Scheme Photocatalyst with Biochar for Emerging Adsorption for Photocatalysis: Multicharge Migration and Mechanistic Insights

Photocatalysis for environmental cleanup applications has seen an enormous increase in interest recently. This study aimed to examine the in situ photoactivity of the photocatalyst BiOI/g-C3N4/Bi2WO6/Biochar for the photocatalytic decomposition of the target pollutant methylene blue (MB). During photocatalysis, biochar is utilized as a support material by using light harvesting and electron-conductive qualities to hinder the quick recombination of e–/h+ pairs. The BiOI/g-C3N4/Bi2WO6/Biochar composite showed improved photoactivity and stability after adding biochar. For MB degradation, the attained rate constant K was found to be 0.04102 > 0.02446 > 0.01818 > 0.0119 > 0.00933 > 0.00705 min–1 for g-C3N4/Bi2WO6/BIOI/Biochar > g-C3N4/Bi2WO6/BIOI > g-C3N4/Bi2WO6 > BiOI > Bi2WO6 > g-C3N4, respectively. The degradation efficiencies of BiOI/g-C3N4/Bi2WO6/Biochar photocatalysts for MB were 97.56% within 70 min. Scavenger and electron spin resonance (ESR) studies further demonstrated that h+, •O2–, and •OH are significant reactive species that aid in the photodegradation of dyes. Additionally, the structural analyses of MB using DFT calculations and the examination of the degraded products using GC-MS (gas chromatography–mass spectrometry) allowed for a more insightful deduction of the photodegradation pathways. Results showed that the degradation efficiencies of BiOI/g-C3N4/Bi2WO6 significantly improved the degradation rate with the addition of biochar. The quaternary composite improved light harvesting, absorption capacity, porosity, and pore structure of the photocatalyst. This work suggests possible applications and a novel technique for large-scale photocatalytic degradation. It also suggests a straightforward and inexpensive strategy for creating a stable semiconductor-based photocatalytic system.