Razzaghi Fatemeh, Debiemme-Chouvy Catherine, Pillier Françoise, Perrot Hubert, Sel Ozlem
Sorbonne Universités, UPMC Univ Paris 06, UMR 8235, Laboratoire Interfaces et Systèmes Electrochimiques, F-75005, Paris, France.
Phys Chem Chem Phys. 2015 Jun 14;17(22):14773-87. doi: 10.1039/c5cp00336a.
Mesoporous WO3 thin films were prepared electrochemically by using an ionic surfactant during the synthesis, and the electrochemical properties are investigated in comparison with their dense analogues. This report specifically highlights the suitability of a time resolved coupled electrogravimetric method to follow meticulously the ion intercalation/extraction phenomena which revealed the enhanced ion intercalation/extraction behavior of electrodeposited mesoporous WO3 thin films for diverse applications in energy storage and electrochromism. This methodology (electrochemical impedance spectroscopy (EIS) and its coupling with a fast quartz crystal microbalance (QCM)) has the ability to detect the contribution of the charged or uncharged species during the electrochemical processes, and to deconvolute the global EQCM responses into the anionic, cationic, and the free solvent contributions. Our study identifies the involvement of several charged species (Li(+), Li(+)·H2O) in the compensation of charge, and H2O molecules indirectly contribute to the process in both dense and mesoporous WO3 thin films. Even a slight contribution of ClO4(-) ions was detected in the case of mesoporous analogues. The results of the study indicate that the transfer resistances of Li(+) and Li(+)·H2O are decreased when the WO3 films are mesoporous. A more significant difference is observed for the larger and partially dehydrated Li(+)·H2O ions, suggesting that increased surface area and pore volume created by mesoporous morphology facilitate the transfer of larger charged species. The relative concentration changes of cations are also magnified in the mesoporous films. The final concentration variations are higher in mesoporous films than that in the dense analogues; ∼4 times and ∼10 times higher for Li(+) and for Li(+)·H2O, respectively. To the best of our knowledge, an unambiguous identification of species other than desolvated cations (e.g. Li(+) ions), the information on their transfer dynamics and quantification of the transferred species have never been reported in the literature to describe the charge compensation process in WO3 based electrodes.
在合成过程中使用离子表面活性剂通过电化学方法制备了介孔WO₃薄膜，并将其电化学性质与其致密类似物进行了比较研究。本报告特别强调了时间分辨耦合电重量法对于精确跟踪离子嵌入/脱出现象的适用性，该现象揭示了电沉积介孔WO₃薄膜在能量存储和电致变色等多种应用中增强的离子嵌入/脱出行为。这种方法（电化学阻抗谱（EIS）及其与快速石英晶体微天平（QCM）的耦合）能够检测电化学过程中带电或不带电物种的贡献，并将整体EQCM响应解卷积为阴离子、阳离子和自由溶剂的贡献。我们的研究确定了几种带电物种（Li⁺、Li⁺·H₂O）参与电荷补偿，并且H₂O分子在致密和介孔WO₃薄膜中均间接对该过程有贡献。在介孔类似物的情况下甚至检测到了ClO₄⁻离子的轻微贡献。研究结果表明，当WO₃薄膜为介孔时，Li⁺和Li⁺·H₂O的转移电阻降低。对于更大且部分脱水的Li⁺·H₂O离子观察到了更显著的差异，这表明介孔形态产生的增加的表面积和孔体积促进了更大带电物种的转移。阳离子的相对浓度变化在介孔薄膜中也被放大。介孔薄膜中的最终浓度变化比致密类似物中的更高；Li⁺和Li⁺·H₂O分别高出约4倍和约10倍。据我们所知，文献中从未报道过除去溶剂化阳离子（例如Li⁺离子）以外的物种的明确鉴定、它们的转移动力学信息以及转移物种的定量，以描述基于WO₃的电极中的电荷补偿过程。
