Ion-Selective Surface Electroconvection in Conjunction with Buoyancy and Polymer Additive Effects

Abstract

In advanced electrochemical systems, salinity gradients are widespread and profoundly affect the energy distribution and stabilities of the system. In our research, we thoroughly investigated the ion-selective surface electroconvection flow coupling with buoyancy effects and polymer additives. The variation in mass transfer properties and energy budgets are also investigated in detail. Our results show that polymer additives act as a destabilising factor in an unstable configuration when Rayleigh number Ra ≤ 1000. When Ra > 1000, polymer additives play a stabilizing role. For ion transport, viscoelasticity decreases the overlimiting current by up to 41% for no buoyancy effects. However, the overlimiting current drops by only 27% at large Ra number. Finally, details of the energy budgets reveal a marked salinity and elasticity dependency. The polymer additives can act as either kinetic energy (KE) sinks or KE sources. For small Weissenberg number Wi, polymer as KE sinks leading to ion transport reduction. For large Wi, the role of polymer changes to EK sources. The nonlinear ion transport can be attributed to role change of polymer in energy analysis. These mechanisms provide greater insight into the role of polymer in prevent premature cell failure and stabilizing electrodeposition.

Keywords: ion-selective surface electroconvection, buoyancy effect, viscoelastic, ion transport, polymer additives