Investigation of a Sodium Hypochlorite Catholyte for an Aluminum Aqueous Battery System

摘要

A solution-phase sodium hypochlorite (NaOCl) cathode for use in an aluminum-based seawater battery is presented. This catholyte attains a high power density, a positive redox potential, and a high Faradaic current capacity. NaOCl is also inexpensive, stable, and environmentally safe/friendly. Four aluminum alloys and 99.999% pure aluminum, serving as anodes, were tested in 3.0, 5.0, and 8.0 M NaOH solutions at the temperatures 45, 55, 65, and 80 ℃. The catholyte concentration and temperature effects were optimized and the best electrocatalyst was chosen to carry out the NaOCl reduction. Optimization experiments were carded out on a half-cell basis using a potentiostat in a three-electrode configuration with Ag/AgCl as the reference electrode and a carbon rod as the counter electrode. Full-cell testing incorporating the optimum conditions was performed with a flowing electrolyte apparatus. A catholyte concentration of 0.70 M NaOCl proved optimum in combination with 3.0 M NaOH at the temperature 55 ℃ and 5.0 M NaOH at the temperature 65 ℃ . The temperature 45 ℃ was not high enough for aluminum activation, the 80 ℃ data did not show an improvement over the 65 ℃ data, and polarization was not dramatically enhanced in 8.0 M NaOH. Nickel foil and porous nickel separately electroplated with palladium were found to be the most effective electrocatalysts. Full-cell data demonstrates a successful electrochemical system with current densities approaching 1200 mA/cm↑(2) and voltages above 1.0V.