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Blue Energy and Desalination with Nanoporous Carbon Electrodes: Capacitance from Molecular Simulations to Continuous Models

Simoncelli, ichele and Ganfoud, Nidhal and Sene, Assane and Haefele, Matthieu and Daffos, Barbara and Taberna, Pierre-Louis and Salanne, Mathieu and Simon, Patrice and Rotenberg, Benjamin Blue Energy and Desalination with Nanoporous Carbon Electrodes: Capacitance from Molecular Simulations to Continuous Models. (2018) Physical Review X, 8 (2). 1-13. ISSN 2160-3308

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Official URL: https://doi.org/10.1103/PhysRevX.8.021024

Abstract

Capacitive mixing (CapMix) and capacitive deionization (CDI) are currently developed as alternatives to membrane-based processes to harvest blue energy—from salinity gradients between river and sea water— and to desalinate water—using charge-discharge cycles of capacitors. Nanoporous electrodes increase the contact area with the electrolyte and hence, in principle, also the performance of the process. However, models to design and optimize devices should be used with caution when the size of the pores becomes comparable to that of ions and water molecules. Here, we address this issue by simulating realistic capacitors based on aqueous electrolytes and nanoporous carbide-derived carbon (CDC) electrodes, accounting for both their complex structure and their polarization by the electrolyte under applied voltage. We compute the capacitance for two salt concentrations and validate our simulations by comparison with cyclic voltammetry experiments. We discuss the predictions of Debye-Hückel and Poisson-Boltzmann theories, as well as modified Donnan models, and we show that the latter can be parametrized using the molecular simulation results at high concentration. This then allows us to extrapolate the capacitance and salt adsorption capacity at lower concentrations, which cannot be simulated, finding a reasonable agreement with the experimental capacitance. We analyze the solvation of ions and their confinement within the electrodes—microscopic properties that are much more difficult to obtain experimentally than the electrochemical response but very important to understand the mechanisms at play. We finally discuss the implications of our findings for CapMix and CDI, both from the modeling point of view and from the use of CDCs in these contexts.

Item Type:Article
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Commissariat à l'Energie Atomique et aux énergies alternatives - CEA (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > Collège de France (FRANCE)
Other partners > Ecole Nationale Supérieure de Chimie de Paris - ENSCP (FRANCE)
Other partners > Ecole Nationale Supérieure de Chimie de Montpellier - ENSCM (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Other partners > Institut polytechnique de Grenoble (FRANCE)
French research institutions > Institut National de la Recherche en Informatique et en Automatique - INRIA (FRANCE)
Other partners > Sorbonne Université (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Other partners > Université de Versailles Saint-Quentin-en-Yvelines -UVSQ (FRANCE)
Other partners > Université de Nantes (FRANCE)
Other partners > Université de Picardie Jules Verne (FRANCE)
Other partners > Université de Pau et des Pays de l'Adour - UPPA (FRANCE)
Other partners > Université de Haute Alsace - UHA (FRANCE)
Other partners > Université de Montpellier (FRANCE)
Other partners > Université Paris-Sud 11 (FRANCE)
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Deposited By: cirimat webmestre
Deposited On:15 Feb 2019 13:25

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