Proton activity in Nafion films: Probing exchangeable protons with methylene blue
Proton activity in Nafion films: Probing exchangeable protons with methylene blue
复制标题
DOI：
10.1021/la0636816
复制
发表时间：
2007-05-08
期刊：
影响因子：
3.9
通讯作者：
Kamat, Prashant V.
中科院分区：
文献类型：
--
作者：
Seger, Brian;Vinodgopal, K.;Kamat, Prashant V.
介绍了一种通过引入亚甲基蓝作为指示剂来监测质子交换膜(Nafion)H+活度的简单方法。该染料的特征吸收峰位于665 nm和745 nm，分别对应于其单质子化形式和双质子化形式。从双质子化亚甲基蓝吸收的出现监测到的Nafion的表观质子活度相当于1.2M H_2SO_4。通过监测与染料质子化平衡相关的光谱变化，可以探测Nafion膜中的速率和可交换的质子位置。对于Nafion 117薄膜，我们估计总的可交换质子位置为2.5×10(19)位/厘米(2)或4.2×10(-5)摩尔/厘米(2)。结合位的H+/Na+交换平衡常数为2.2。探讨了用亚甲基蓝作为探针监测直接甲醇燃料电池运行中质子活度的可行性。
A simple approach to monitor the H+ activity of a proton-exchange membrane (Nafion) is introduced by incorporating methylene blue as an indicator dye. The dye exhibits characteristics absorption maxima at 665 and 745 nm corresponding to its singly and doubly protonated forms, respectively. The apparent proton activity of Nafion as monitored from the appearance of doubly protonated methylene blue absorption is equivalent to 1.2 M H2SO4. By monitoring the spectral changes associated with the protonation equilibrium of the dye, it is possible to probe the rate and the exchangeable proton sites within the Nafion film. For the Nafion 117 film, we estimate the total exchangeable proton sites to be 2.5 x 10(19) sites/cm(2) or 4.2 x 10(-5) mols/cm(2). The equilibrium constant for the H+/Na+ exchange for the bound sites is determined to be 2.2. The feasibility of methylene blue as a probe to monitor proton activity during the operation of a direct methanol fuel cell has been explored.