Revisiting the natural convection effects at ultra-low redox concentration solutions: The influence of viscosity and diameter of wire electrode

Natural convection could arise even at ultra-low redox concentration solutions (1–10 mM). Models such as convection–diffusion layer model and spontaneous convection model have been established to describe this phenomenon. However, the driving forces as well as the parameters that influence this natural convection effects are still not clear. Herein we investigated the effects of viscosity on natural convection by introducing sodium alginate (SA), which enhanced viscosity without changing the diffusion coefficient of the redox couple. Resultantly, it allowed us to obtain the relationship between microscopic flow of solutions and the thickness of natural convection layer. Moreover, wire electrodes with various diameters were also tested to reveal the natural convection effects on mass transfer. An empirical equation was established to describing the influences of solution viscosity and diameter of wire electrode on the thickness of natural convection layer in ultra-low redox concentration solutions.