Electrochemical synthesis of layered manganese oxides intercalated with tetraalkylammonium ions
Electrochemical synthesis of layered manganese oxides intercalated with tetraalkylammonium ions
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DOI：
10.1021/la048173f
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发表时间：
2005-01-04
期刊：
影响因子：
3.9
通讯作者：
Ogura, K
中科院分区：
文献类型：
--
作者：
Nakayama, M;Konishi, S;Ogura, K
用一步电化学方法在铂电极上制备了具有不同层间距的水钠锰矿型层状锰氧化物薄膜。该过程涉及在具有不同烷基链长度的四烷基铵阳离子存在下在约+1.0 V（Ag/AgCl）下恒电位氧化水性Mn 2+离子。X-射线衍射表明，四丁基铵（TBA），四丙基铵（TPA），和四乙基铵（TEA）离子沉积的薄膜是由一个单一的相，其中未水合的四烷基铵离子被容纳作为一个单层之间的锰氧化物层。产物的层间距按TEA < TPA < TBA的顺序增大。与四甲基铵（TMA）沉积的膜是两个相的混合物有关的水合和未水合的客体阳离子，前者是主要的可能是由于较低的疏水性能的TMA相比，其他四烷基铵离子。TBA（+）-插层的Mn氧化物膜涂覆的电极在0和+0.8V之间的KCl溶液中表现出良好的充电/放电性能。在这种情况下，Mn氧化物层之间的TBA（+）离子通过离子交换被溶液中的K+迅速取代，伴随着中间层的收缩。结合的K+离子以及质子在氧化物层中Mn 4+和Mn 3+之间的电化学转化中起重要作用。在TBACl溶液中，层间TBA（+）离子可以在正向扫描期间被电化学排除，伴随着Mn 3+位点的氧化。这导致阳极电流和伴随的中间层收缩。然而，在反向扫描中，压缩的夹层不允许从电解质中掺入大体积的TBA（+）离子，几乎没有观察到阴极电流。两种电解质之间的电化学行为的这种明显差异可以通过考虑大部分Mn氧化物表面存在于层状结构内部而不是外表面上来识别。这表明在整个膜上形成了层状结构。
Thin films of birnessite-type layered manganese oxides with various interlayer spacings have been prepared on a platinum electrode by a one-step electrochemical procedure. The process involves a potentiostatic oxidation of aqueous Mn2+ ions at around +1.0 V (Ag/AgCl) in the presence of tetraalkylammonium cations with different alkyl chain lengths. X-ray diffraction indicates that the films deposited with tetrabutylammonium (TBA), tetrapropylammonium (TPA), and tetraethylammonium (TEA) ions are composed of a single phase where unhydrated tetraalkylammonium ions are accommodated as a monolayer between manganese oxide layers. The interlayer spacing of the products increases in an order of TEA < TPA < TBA. The film deposited with tetramethylammonium (TMA) is a mixture of two phases relating to hydrated and unhydrated guest cations, the former being predominant probably as a result of less hydrophobic property of TMA compared to that of other tetraalkylammonium ions. The TBA(+)-intercalated Mn oxide film-coated electrode exhibits a good charge/discharge property in a KCl solution between 0 and +0.8 V. In this case, TBA(+) ions between the Mn oxide layers are rapidly replaced with K+ in solution by ion exchange, accompanying a shrinkage of the interlayer. The incorporated K+ ions as well as protons play an important role in the electrochemical conversion between Mn4+ and Mn3+ in the oxide layer. In the TBACl solution, the interlayer TBA(+) ions can be excluded electrochemically during the positive-going scan, concomitant with the oxidation of Mn3+ Sites. This causes an anodic current and the accompanying shrinkage of the interlayer. On the reverse scan, however, the compressed interlayer does not allow the incorporation of bulky TBA(+) ions from the electrolyte, with virtually no cathodic current observed. Such an obvious difference in electrochemical behavior between the two electrolytes can be recognized by considering that most of the Mn oxide surface is present inside the layered structure, not on the external surface. This indicates that the layered structure is formed over the entire film.