Photocatalytic destruction of Congo red dye in wastewater using a novel Ag2WO4/Bi2S3 nanocomposite decorated g-C3N4 nanosheet as ternary S-scheme heterojunction: Improving the charge transfer efficiency

Herein, a novel S-scheme g-C3N4/Ag2WO4/Bi2S3 (CN/AW/BS) heterojunction was fabricated using multistep approaches. The successful construction of CN/AW/BS was verified using XRD, XPS, HRTEM technologies. The g-C3N4 support demonstrated its vital contribution for improving the surface characteristics of CN/AW/BS by inhibiting the aggregation impacts of immobilized Ag2WO4/Bi2S3 nanorods. The DRS, photocurrent, EIS, and PL spectra stated that the coupling of g-C3N4 nanosheets with Ag2WO4/Bi2S3 exhibited a dramatic improvement in the optical and photoelectrochemical properties as compared with bare g-C3N4 nanosheets. The photo-degradation activity was examined by degrading Congo red under 140 W of LED illumination. The ternary photocatalyst exhibited the best degradation performance (98 % in 60 min), which is about 2.86, 4.09, 6.19, and 1.67 times greater than g-C3N4, Ag2WO4, Bi2S3, CN/AW/BS, respectively. The environmental parameters that affect the photoreaction, such as CN/AW/BS loading, Congo red concentration, and solution pH, were also evaluated. The photostability of the CN/AW/BS composite was demonstrated by maintaining 85 % of its original efficiency after five subsequent Cong red degradation cycles. The suggested dual-S-scheme electron pathway was justified by trapping and ESR results, which certify that (OH)-O-center dot, O-center dot(2),(-) and h(+) played a vital role in Congo red oxidation. In addition, the Congo red degradation pathways were well explained, and the degraded intermediates were also identified. According to comparison studies, efficient Congo red degradation can be achieved in a short period of time and with a lower power consumption. The dual-S-scheme heterojunction proved its superiority by providing a perfect dual S-scheme path for electrons and holes migration in the ternary system.