Bi ₁₃ S ₁₈ X ₂ (X = Br, I) Nanoneedles with Piezoelectric Effect for Efficient Photocatalytic Marine Antifouling

The beneficial impact of the piezoelectric effect, arising from internal polarization, on the photocatalytic performance has been extensively documented. In this study, Bi 13 S 18 Br 2 and Bi 13 S 18 I 2 nanoneedle-like photocatalysts with piezoelectric effect were successfully synthesized via a coprecipitation method, and their potential as antibacterial agents for marine antifouling applications was investigated. The experimental results showed that under simultaneous exposure to light and simulated wave-induced mechanical stimulation, the piezo-photocatalytic antibacterial rates of Bi 13 S 18 Br 2 and Bi 13 S 18 I 2 against Pseudomonas aeruginosa could reach 100% and 97.9%, respectively, and against Staphylococcus aureus could reach 95.5% and 91.7%, respectively. Moreover, radical trapping experiments and electron spin resonance (ESR) results revealed that superoxide radicals (•O 2 – ) and photogenerated holes (h + ) were the primary reactive species during the piezo-photocatalytic antibacterial process. Density functional theory (DFT) calculation results elucidated the structural and electronic differences between Bi 13 S 18 Br 2 and Bi 13 S 18 I 2, revealing that the halogen atoms indirectly modulate the band structure of the Bi–S framework by influencing the orbital hybridization, which, in turn, affects light absorption. In addition, due to the low electron localization function (ELF) localization of Br, it optimized the electron–phonon coupling and carrier migration efficiency of Bi 13 S 18 Br 2, thereby endowing it with superior piezoelectric performance compared to Bi 13 S 18 I 2 . This work provided insights into the in-depth structural understanding of Bi 13 S 18 Br 2 and Bi 13 S 18 I 2 and also offered suggestions for developing high-efficiency marine antifouling piezo-photocatalysts through rational structural design.