Fabrication of SiW9Co3–Bi4O5Br2 photocatalysts with improved charge separation for visible-light-driven hydrogen evolution and metronidazole degradation: Characterization, mechanism, and toxicity assessment
Rahila Batul, Waqed H. Hassan, Dheyaa J. Jasim, Pradeep Kumar Singh, Shatha A. Aldaghfag, Mohamed Ayadi, Ibrahm Mahariq, Mukhtorjon Karimov, Otabek Mukhitdinov, Alisher Abduvokhidov, Reda A. Haggam
Abstract
The rational design of efficient photocatalysts for clean energy generation and environmental remediation remains a significant challenge. In this study, a novel SiW 9 Co 3 –Bi 4 O 5 Br 2 heterostructure photocatalyst was successfully synthesized using a simple hydrothermal–self-assembly method. The structural, morphological, and optical properties were thoroughly investigated using techniques such as XRD, FTIR, Raman, XPS, SEM, TEM, and UV–Vis DRS. SiW 9 Co 3 clusters were uniformly anchored on the surface of Bi 4 O 5 Br 2 nanosheets, forming heterojunction interfaces that facilitated charge transfer and suppressed electron–hole recombination. Under visible light, the optimized SiW 9 Co 3 –Bi 4 O 5 Br 2 (20 wt%) composite exhibited superior photocatalytic performance, achieving H 2 evolution rate of 570 μmol·g −1 ·h −1 , significantly higher than that of pristine Bi 4 O 5 Br 2 . Simultaneously, 98.05 % of metronidazole (25 mg·L −1 ) was degraded within 80 min. Radical scavenging and ESR results confirmed that •O 2 − and •OH were the dominant species responsible for H 2 generation and pollutant degradation. The Z -scheme mechanism was proposed, where photogenerated electrons in SiW 9 Co 3 reduce H + to H 2 , while holes in Bi 4 O 5 Br 2 oxidize metronidazole. Additionally, the photocatalyst demonstrated high stability, with minimal performance degradation after five cycles, and XRD confirmed its structural integrity after cycling, supporting its potential for long-term, sustainable applications in both energy and environmental fields.