de Andrade Neto Nivaldo Freire, da Silva Joyce Marina Paiva, da Cunha João Marcelo Soares, Teodoro Marcio Daldin, Corrêa Marcio Assolin, Bomio Mauricio R D, da Motta Fabiana Villela
LSQMLaboratory of Chemical Synthesis of MaterialsDepartment of Materials Engineering, Federal University of Rio Grande do NorteUFRN, P.O. Box 1524, 59078-970 Natal, RN, Brazil.
Department of Physics, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil.
ACS Omega. 2025 Aug 27;10(35):40364-40378. doi: 10.1021/acsomega.5c05699. eCollection 2025 Sep 9.
This study investigated the sonochemical synthesis of bismuth ferrite (BFO) systems, focusing on how varying EDTA concentrations influence crystalline phases and photocatalytic performance. X-ray diffraction (XRD) analysis showed that 33EDTA uniquely formed single-phase BiFeO, while other EDTA concentrations resulted in secondary phases like BiFeO and BiFeO. EDTA concentration was crucial for phase control, with higher concentrations favoring the BiFeO phase (67.8% phase for 100EDTA sample). All samples exhibited consistent band gap energies (2.25-2.28 eV), indicating visible light absorption. X-ray photoelectron spectroscopy (XPS) revealed increased oxygen vacancy concentrations in multiphase samples due to secondary phases and heterojunctions. Magnetic characterization showed an almost magnetic behavior in 33EDTA and 100EDTA ( of 0.0002 and 0.001 emu/g), with higher BiFeO content contributing to increased magnetism in 100EDTA. Photoluminescence (PL) measurements indicated higher electron-hole recombination in single-phase 33EDTA compared to multiphase samples with heterojunctions. Photocatalytic tests with methylene blue (MB) showed that at neutral pH, multiphase samples generally had higher, though still low, efficiency due to heterojunctions, degrading approximately 46% for the 100EDTA sample. Despite poor performance at neutral pH (32%), single-phase 33EDTA exhibited significantly improved photocatalytic activity at pH 3, achieving complete MB degradation after 120 min. This was attributed to the positive surface charge at lower pH, minimizing adsorptive effects. Mechanistic studies confirmed both electrons and holes are active in pure BiFeO photocatalysis, while heterojunctions primarily limited the mechanism to superoxide formation in multiphase samples.
本研究调查了铁酸铋（BFO）体系的声化学合成，重点关注不同乙二胺四乙酸（EDTA）浓度如何影响晶相和光催化性能。X射线衍射（XRD）分析表明，33EDTA独特地形成了单相BiFeO，而其他EDTA浓度则导致了诸如BiFeO和BiFeO等次生相。EDTA浓度对于相控制至关重要，较高浓度有利于BiFeO相（100EDTA样品的相含量为67.8%）。所有样品均表现出一致的带隙能量（2.25 - 2.28电子伏特），表明具有可见光吸收能力。X射线光电子能谱（XPS）显示，由于次生相和异质结，多相样品中的氧空位浓度增加。磁性表征表明，33EDTA和100EDTA呈现出几乎磁性的行为（分别为0.0002和0.001emu/g），100EDTA中较高的BiFeO含量导致磁性增强。光致发光（PL）测量表明，与具有异质结的多相样品相比，单相33EDTA中的电子 - 空穴复合更高。用亚甲基蓝（MB）进行的光催化测试表明，在中性pH值下，由于异质结，多相样品的效率通常较高，尽管仍然较低，100EDTA样品的降解率约为46%。尽管在中性pH值下性能较差（32%），但单相33EDTA在pH为3时表现出显著提高的光催化活性，在120分钟后实现了MB的完全降解。这归因于较低pH值下的正表面电荷，使吸附效应最小化。机理研究证实，在纯BiFeO光催化中电子和空穴均具有活性，而异质结主要将多相样品中的机理限制为超氧化物的形成。
