Effect of Strong Acid Functional Groups on Electrode Rise Potential in Capacitive Mixing by Double Layer Expansion
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- 作者：Marta C. Hatzell ; Muralikrishna Raju ; Valerie J. Watson ; Andrew G. Stack ; Adri C. T. van Duin ; Bruce E. Logan
- 刊名：Environmental Science & Technology
- 出版年：2014
- 出版时间：December 2, 2014
- 年：2014
- 卷：48
- 期：23
- 页码：14041-14048
- 全文大小：448K
- ISSN：1520-5851
文摘
The amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10鈥?) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g鈥?) had a positive rise potential of 59 卤 4 mV in the LC solution, whereas the carbon with the highest concentration (0.36 mmol g鈥?) had a negative rise potential (鈭?1 卤 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 卤 2 mV (unaltered) to 鈭? 卤 0.5 mV (oxidized), producing a whole cell potential (53 卤 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 卤 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. These results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons.