Enhanced acidity and pH-dependent surface charge characterization of successively oxidized graphite oxides
Enhanced acidity and pH-dependent surface charge characterization of successively oxidized graphite oxides
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DOI：
10.1016/j.carbon.2005.08.005
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发表时间：
2006-03-01
期刊：
影响因子：
10.9
通讯作者：
Dékány, I
中科院分区：
文献类型：
--
作者：
Szabó, T;Tombácz, E;Dékány, I
这项pH-电位法研究探讨了氧化石墨(GO)水分散体经过一系列氧化处理后，影响表面电荷形成的因素。表面电荷曲线表明，在所研究的整个pH范围内，GO的片状表面都带负电荷。虽然这些曲线与GO悬浮液的浓度无关，但它们受溶液条件的影响很大：增加pH和离子强度会促进酸性表面中心的解离，因为较弱的官能团逐渐参与离子交换过程，而电解液为表面电荷提供了有效的屏蔽。解离官能团的表面密度由GO样品的质子结合等温线和比表面积决定。BET表面积为场地密度提供了不合理的高值，而通过几何考虑计算的表面积则提供了可接受的场地密度。红外光谱和元素分析表明，氧化后的氧化过程中形成越来越多的含氧基团，导致氧化石墨的酸性增强。(C)2005爱思唯尔有限公司。保留所有权利。
This pH-potentiometric study explores the factors influencing the surface charge developed in aqueous dispersions of graphite oxide (GO) after a series of oxidation treatments. Surface charging curves demonstrate that lamellar surfaces of GO are negatively charged in the entire pH range studied. While these curves were found to be independent from the concentration of the GO suspensions, they were greatly affected by the solution conditions: increasing the pH and the ionic strength promotes the dissociation of acidic surface sites as weaker functional groups progressively participate in the ion exchange process, and the electrolyte provides an effective shielding for the surface charge. Surface densities of dissociated functional groups were determined by the proton binding isotherms and the specific surface areas of GO samples. BET surface areas provided irrationally high values for site densities, while surface areas calculated by geometrical considerations gave acceptable site densities. Formation of more and more oxygen-containing groups upon the subsequent oxidation steps, detected by IR spectroscopy and elemental analysis, resulted in the enhanced acidity of graphite oxide. (C) 2005 Elsevier Ltd. All rights reserved.