期刊
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
卷 870, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jelechem.2020.114243
关键词
Electrical double layer; Double layer capacitance; Potential of zero charge; Poisson-Nernst-Planck theory
资金
- National Natural Science Foundation of China [21802170]
The method of obtaining double-layer capacitance (C-dl) and the potential of zero charge (pzc) from voltammetry is examined numerically using a modified Poisson-Nernst-Planck theory considering ion steric effect and natural convection. A prerequisite of this method is that the pure double-layer charging region is well separated from interfacial reactions (such as hydrogen adsorption/desorption at Pt), if any. An additional tacit assumption is that the double layer reaches equilibrium at each potential during the potential scanning. The equilibrium assumption is violated to a greater extent when the potential scanning is faster because ion transport is more retarded, bringing into greater errors into the results obtained. A key quantity related to the equilibrium assumption is the time constant of double-layer charging which is given by, t(0) = n lambda delta/D (n is a potential-dependent coefficient around 20, lambda. the Debye length, delta the thickness of diffusion layer, D the diffusion coefficient). Also discussed is how interfacial reactions hinder the double layer from achieving equilibrium. Considerations on optimizing the experimental setup for determining C-dl and pm from voltammetry are presented.
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