Dynamics of two-metal codeposition inside a flow-through porous electrode at a high solution flow rate

Using the expanded dynamic model of a liquid flow-through porous electrode (PE), we studied the effect of the parameters of the polarization curve and the potentiostatic mode of electrolysis on the dynamics and final parameters of the codeposition of two metals (М1 and М2). The direct-flow and circulation operation modes of the equipotential PE are considered at the high solution flow rate and in the absence of the anodic dissolution of the electronegative component М2. It has been shown that the time-constancy of the rates of М1 and М2 deposition averaged over the PE thickness is characteristic of the direct-flow mode. However, this does not mean that the local rates of metal deposition are constant. A general trend is a decrease in the rate of metal deposition with time in the rare part of the PE and its increase in the front region, which is closest to the anode. The transition to the circulation mode and small solution volumes leads, along with the expected consequences (a decrease in the rate of metal deposition with time and an increase in the time within which the porous matrix is filled with the deposit), to a more uniform distribution of the electropositive component М1 and a sharp broadening of the region of deposition of the electronegative component М2. The experimental data on the dynamics of the codeposition of Ag and Cu from dilute thiosulfate solutions are in good agreement with modeling results.

► Dynamics of two-metal codeposition inside a flow-through porous electrode.
► Regularities of the mutual influence of the partial currents of separate components.
► Constant average and variable local deposition rates of metals in the direct-flow mode.
► Much more uniform metal distribution if the circulating solution has a small volume.
► Qualitative agreement between the modeling and experimental results.