Do Concentration Cells Store Charge in Water? Comment on Can Water Store Charge?

In a recent article, Ovchinnikova and Pollack (O&P)(1) reported that the persistent pH gradients (>100 min after electrolysis) generated upon charging a simple electrolytic cell (Pt electrodes in dilute aqueous NaCl solutions) imply that “water can store charge”, in apparent violation of the principle of electroneutrality in bulk macroscopic fluid phases

Fenómenos de transporte en soluciones concentradas de poliestirensulfonato de forma iónica mixta sodio-cesio

Fil: Corti, Horacio R.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Electrochemistry in supercritical trifluoromethane

The use of trifluoromethane (CHF3) as a solvent for electrochemical studies in supercritical conditions is analyzed. The dielectric and electrical conductivity of supercritical CHF3 was measured at 323.15 K at several densities. The solubility and electrical conductivity of tetrabutylammonium hexafluorophosphate (TBAPF6) and decamethylferrocenium hexafluorophosphate (Fe(Cp*)2PF6) in supercritical CHF3 were measured at 323.15 K as a function of density. It was found that, in spite of the high ion pair formation of the TBAPF6 in the supercritical solvent, this salt is a suitable supporting electrolyte, having a conductivity much higher than that reported for other electrolytes in low dielectric constant supercritical solvents. The limiting currents measured for decamethylferrocene (Fe(Cp*)2) and decamethylferrocenium hexafluorophosphate (Fe(Cp*)2PF6) at a platinum microdisc in supercritical CHF3 at several densities and 323.15 K, show the feasibility of using the proposed supercritical system as a model for electrochemical studies in variable density media. The effect of concentration of the supporting electrolyte on the limiting current at the microelectrode is qualitatively discussed in terms of a recent theory which takes into account the ion association of the supporting and electroactive electrolytes. Keywords: Supercritical trifluoromethane, Electrical conductivity, Decamethylferrocenium hexafluorophosphate, Tetrabutylammonium hexafluorophosphate, Limiting current, Microelectrode