Energy Extraction from Capacitive Mixing. Experimental and Computational Analysis of Chemical Aspects

CABRERA, JORGE NICOLAS; GONZALEZ, GRACIELA; LIZARRAGA, LEONARDO; NEGRI, R. MARTÍN

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

ELECTROCHEMICAL SOC INC

Año: 2022 vol. 169 p. 40506 - 40514

0013-4651

AbstractThe double-layer expansion at the interfaces of charged electrodes when a concentrated salt solution (molar concentration Csalt) is replaced by a diluted solution (Cfresh), produces an increase of the cell voltage. Experiments and simulations were performed in order to study the effect of several variables on the obtained transient voltage, V(t), and the rising of voltage at equilibrium, Δφeq. Carbon electrodes were prepared and characterized by cyclic voltammetry, amperometry, and N2-adsorption isotherms. The experimental results and finite elements simulations show that the shape of V(t) is influenced by the diffusion coefficients of the ions. On the other hand, experiments and simulations indicate that Δφeq present a Nernstian-like dependence with the dilution coefficient, Cdil = Csalt/Cfresh, while is independent of the initial charge and charging time. Quantitative features are interpreted by proposing a partial blocking of the electrodes for the dilution process, associated to irreversible incorporation of solution into the porous, presenting a model to estimate the blocking degree. Finally, cycles of charging-dilution-work-concentration were performed, extracting energies in the order of 100 μJ cm−2, which are in agreement with the model equations as function of Csalt and Cfresh.