Electric Double Layer at the Polycrystalline Platinum–Electrolyte Interface Probed by the Electrokinetic Streaming Current Method
Electric Double Layer at the Polycrystalline Platinum–Electrolyte Interface Probed by the Electrokinetic Streaming Current Method
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DOI：
10.1021/acs.jpcc.1c04666
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
Prantik Saha;I. Zenyuk
中科院分区：
文献类型：
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作者：
Prantik Saha;I. Zenyuk
用电化学-电动力学方法研究了多晶铂（poly-Pt）-非吸附电解质界面扩散层的界面电荷和离子电导率。假设没有特定的离子吸附，金属上的电子电荷（金属电荷）被发现单调增加的酸性，中性和碱性pH值，与所施加的电位高达0.95 V相对于SHE。没有观察到非单调的金属充电，但是，金属电荷被发现饱和到一个接近恒定的正值在较高的施加电位，可能是由于离子拥挤的扩散层。相对于Pt的零自由电荷的电位，在zeta电位为0的电位被发现是在酸性pH值较低，较高的碱性pH值，几乎相等的中性pH值。此外，氧化物覆盖率计算从循环伏安法，和H-覆盖率计算从Frumkin吸附等温线。将它们添加到金属电荷中以计算“总电荷”，并与文献中Pt（111）的CO置换结果进行比较。这两种方法的结果显示出良好的一致性，电动法适用于更大的电位窗口（V> 0.75 V）。在扩散层中的离子电导率被发现是最小的zeta电位为0时，在所施加的电位，其值是等于电解质的体积离子电导率。对于所有其他施加的电位，扩散层离子电导率较高。
Interfacial charging and ionic conductivity in the diffuse layer of polycrystalline platinum (poly-Pt)– nonadsorbing electrolyte interface were studied using a combined electrochemical–electrokinetic method. Assuming no specific adsorption of ions, the electronic charge on the metal (metal charge) was found to increase monotonically for acidic, neutral, and basic pH, with the applied potential up to 0.95 V versus SHE. Nonmonotonic metal charging was not observed; however, the metal charge was found to saturate to a near-constant positive value at higher applied potentials, possibly due to ion crowding in the diffuse layer. With respect to the potential of zero free charge of Pt, the potential at which the zeta potential was 0 was found to be lower in acidic pH, higher in basic pH, and almost equal in neutral pH. In addition, oxide coverage was calculated from cyclic voltammetry, and H-coverage was calculated from Frumkin adsorption isotherms. They were added to the metal charge to calculate the “total charge” and were compared with the CO displacement results for Pt(111) from the literature. The results from these two methods showed good agreement, with the electrokinetic method being applicable for a larger potential window (V> 0.75 V). Ionic conductivity in the diffuse layer was found to be minimum at applied potentials where the zeta potential is 0, and its value was equal to the bulk ionic conductivity of the electrolyte. For all the other applied potentials, diffuse layer ionic conductivity was higher.