Year-end Sale % OFF 
Abstract
Capacitive deionization (CDI) has become an important research topic in terms of water purification as it is a cost- and energy efficient approach for the desalination of brackish water. Carbon- based materials are often used as electrodes in this process due to a variety of morphologies and their suitable performance in this field. In recent studies it has been already shown that a conscientiously chosen set of electrode properties has an enormous effect on the performance behavior of CDI cells. However, most of the studies focus on the optimization of the electrosorption capacity, while the question on how material properties influence the kinetic behavior of a CDI setup has been less intensively studied so far. Here we show that the kinetic effects of electrode materials can be studied in great detail by using electrochemical impedance spectroscopy (EIS). EIS studies of CDI electrodes have been reported before, however, in contrast to these we introduce a method of presenting and analyzing EIS results. This is especially suitable for extracting the frequency ranges in which different rate limiting mechanisms dominate. The new Nyquist Incline Frequency plot (NIF) shows the local slope of the Nyquist plot in dependency of the applied frequency. By this, electron transfer and mass transfer mechanisms which show a characteristic slope in the classical Nyquist plot can be directly visualized together with the information in which time domain they occur. The data derived from the new EIS plot show a clear correlation to pore size distributions from BET measurements, as well as effective capacities and electrosorption kinetics, extracted from CDI experiments. Therefore, we think that by using the NIF plot electrode materials for CDI processes can be conveniently characterized and compared within a single diagram, helping to standardize CDI material development.
Highlights
The process of capacitive deionization (CDI) is a highly efficient and cost effective process which is based on the potential controlled removal of salt or charged contaminants form aqueous solutions (Anderson et al, 2010; Porada et al, 2012; Biesheuvel et al, 2015; Suss et al, 2015; He et al, 2018; Gupta et al, 2019)
In this paper we investigated how material properties influence the kinetics of Capacitive deionization (CDI) by using a new method to interpret electrochemical impedance spectroscopy (EIS) measurements
That in case of nanoporous carbon fibers, the kinetic properties are determined by the way how these fibers are macroscopically arranged
Summary
The process of capacitive deionization (CDI) is a highly efficient and cost effective process which is based on the potential controlled removal of salt or charged contaminants form aqueous solutions (Anderson et al, 2010; Porada et al, 2012; Biesheuvel et al, 2015; Suss et al, 2015; He et al, 2018; Gupta et al, 2019). Examples are nitrogen-doped mesostructured carbons (Xu et al, 2019a), three dimensional graphene frameworks (Xu et al, 2016a), highly ordered mesoporous carbon nanopolyhedra (Xu et al, 2019c) or carbon spheres with hierarchical micro/mesopores (Xu et al, 2016b) Another approach for CDI electrode materials are carbon-based materials doped by heteroatoms like nitrogen or iron (Xu et al, 2020a). Like the Nyquist plot the NIF plot shows characteristic curve shapes for different rate limiting mechanism, such as exhausted capacity, diffusion, or electrolyte resistance. In contrast to the Nyquist plot, the NIF plot directly shows the frequency range in which these mechanisms dominate
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
