Influences of Fe-Mn ratio on the photocatalytic performance of wolframite (FexMn1-xWO4)
Influences of Fe-Mn ratio on the photocatalytic performance of wolframite (FexMn1-xWO4)
复制标题
Fe-Mn配比对黑钨矿(FexMn1-xWO4)光催化性能的影响
DOI：
10.1016/j.chemgeo.2021.120253
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发表时间：
2021
期刊：
影响因子：
3.9
通讯作者：
Xiang Ji
中科院分区：
文献类型：
--
作者：
Linghui Li;Yanzhang Li;Yan Li;Huan Ye;Anhuai Lu;Hongrui Ding;Changqiu Wang;Qiming Zhou;Juanxian Shi;Xiang Ji
天然半导体矿物广泛分布于表生环境中，并以其太阳驱动的氧化还原活动而闻名，其中黑钨矿（FexMn1-xWO4）作为一个有趣的成员却很少受到关注。在这项工作中，研究了 FexMn1-xWO4 系列样品 (x = 1, 0.74, 0.48, 0.24, 0) 受其晶体化学性质影响的半导体光催化活性。通过紫外-可见漫反射（DRS）测量，MnWO4、Fe0.24Mn0.76WO4、Fe0.48Mn0.52WO4、Fe0.74Mn0.26WO4 和 FeWO4 的带隙分别为 2.7、2.4、2.3、2.2 和 2 eV，当 x 从 0 增加时，这些带隙线性减小（R2= 0.971） 1.密度泛函理论（DFT）计算进一步表明，随着Fe含量的增加，价带最大值（VBM）的贡献逐步被Fe 3d轨道占据，带隙因此逐渐减小。研究了 FexMn1-xWO4 样品对亚甲基蓝（MB，5 mg/L）降解的光催化活性。 Fe0.74Mn0.26WO4体系的MB去除率最高，分别比MnWO4、Fe0.24Mn0.76WO4、Fe0.48Mn0.52WO4和FeWO4快3.2、1.9、1.2和1.5倍。电子顺磁共振(EPR)测量检测到FexMn1-xWO4产生的羟基自由基(·OH)浓度与MB的降解率呈正相关。当•OH被去除后，降解速率减慢，表明•OH是MB光催化氧化降解中的主要活性氧。 X射线光电子能谱（XPS）和光致发光（PL）光谱表明，性能最好的Fe0.74Mn0.26WO4光催化产生最多的·OH，这与其最丰富的氧空位缺陷密切相关。由此可见，窄带隙和适当的氧空位可以对光催化性能的提高产生协同效应。该研究有助于深入了解晶体化学在黑钨矿半导体性能和光催化活性中的作用，也为利用天然矿物控制环境污染提出了新策略。
Natural semiconducting minerals are widely distributed in supergene environments and are famous for their solar-driven redox activities, in which wolframite (FexMn1-xWO4) as a fascinating member got less attention. In this work, the semiconducting photocatalytic activities of FexMn1-xWO4series samples (x = 1, 0.74, 0.48, 0.24, 0) influenced by their crystal chemistry were investigated. The bandgaps of MnWO4, Fe0.24Mn0.76WO4, Fe0.48Mn0.52WO4, Fe0.74Mn0.26WO4and FeWO4as measured by UV–vis diffuse reflection (DRS), were 2.7, 2.4, 2.3, 2.2, and 2 eV, respectively, which were linearly decreased (R2= 0.971) when x increased from 0 to 1. The density functional theory (DFT) calculations further indicated with the increasing content of Fe, the contribution of valence-band maximum (VBM) was stepwise occupied by Fe 3d orbits and the bandgap was thus gradually decreased. The photocatalytic activities of FexMn1-xWO4samples were examined on the degradation of methylene blue (MB, 5 mg/L). The MB removal rate was the highest in Fe0.74Mn0.26WO4system, which was 3.2, 1.9, 1.2, and 1.5 times faster than that of MnWO4, Fe0.24Mn0.76WO4, Fe0.48Mn0.52WO4, and FeWO4, respectively. The concentration of produced hydroxyl radical (•OH) by FexMn1-xWO4, detected in electron paramagnetic resonance (EPR) measurement, had a positive correlation with the degradation rate of MB. The degradation rate slowed down when •OH was removed, demonstrating that •OH was the major reactive oxygen species in the photocatalytic oxidative degradation of MB. The best-performing Fe0.74Mn0.26WO4photocatalytically produced the most •OH, which was closely linked with its most abundant oxygen-vacancy defects, revealed by X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. It thus can be concluded that narrow bandgap and appropriate oxygen vacancies can give rise to synergistic effect on the improvement of photocatalytic performance. This study helps get insight into the role of crystal chemistry in semiconducting properties and photocatalytic activities of wolframite, which also puts forward a new strategy to control environmental pollution by using natural minerals.