3D flower-like silica@BiOBr photocatalyst with tunable structure for photocatalytic applications

The growth pathway of layered BiOBr nanosheets was investigated through structural regulation, by which a three-dimensional flower-like BiOBr architecture was constructed and subsequently anchored onto a diatomite (DTE) substrate to form a three-dimensional flower-like Silica@BiOBr composite photocatalyst for the degradation of tetracycline hydrochloride (TCH), a persistent antibiotic contaminant. The optimized DTE@BiOBr achieved a degradation efficiency of 98.5%, markedly surpassing that of pristine BiOBr. Electrochemical analyses revealed that the introduction of diatomite significantly reduced the charge-transfer resistance and enhanced the transient photocurrent response by approximately threefold, indicating more efficient charge separation and migration. The hydroxyl and amide oxygen atoms in TCH were identified by Density Functional Theory (DFT) calculations as the principal reactive centers, while the radical-scavenging experiments indicated that h⁺, ·O₂⁻, and ·OH were the dominant oxidative species involved. The degradation followed an electron-transfer-induced radical cleavage mechanism, where ·O₂⁻ preferentially attacked the carbonyl and amino groups, leading to progressive bond cleavage and eventual mineralization into CO₂ and H₂O. Fourier-transform infrared (FTIR) spectra exhibited an overall downward shift after reaction, confirming the decomposition of TCH into smaller molecular intermediates. This work provides mechanistic insight into the interfacial charge regulation and structural optimization of BiOBr-based photocatalysts for efficient antibiotic wastewater treatment.