Simulation studies on a rotating ring disk electrode system: Role of supporting electrolyte in determination of relevance of ionic migration

Abstract

Most of the past theoretical works with the rotating ring disk electrode (RRDE) system have been restricted to situations where supporting electrolyte concentration is large enough so that the effects of migration of ionic species in the solution becomes negligible. In this work, effects of ionic migration have been investigated for a RRDE system by solving the differential equations describing mass transfer in presence of ionic migration using numerical technique. Two cases were considered for simulation, presence and absence of migration of ionic species. Results indicate that in presence of migration, collection efficiency of a RRDE system increases for all electrode geometries and concentration boundary layer thickness reduces. Results also indicate that collection efficiency is dependent on electrode geometries. The system chosen for simulation is copper sulfate solution of 0.1 (M) concentration with little supporting electrolyte. It is also noticed that migration effect remains important for supporting electrolyte concentration as high as 0.1 (M). Limiting current condition was assumed.

Simulation studies on a rotating ring disk electrode: Effects of ionic migration with kinetic complication‐disk results

“…In this work, he showed that in presence as well as in absence of ionic migration cases, the collection efficiency rises with rising ring thickness. 3 He also stated that collection efficiency falls with increasing gap thickness for both presence and absence of ionic migration cases. 3 Parikh et al 6 used orthogonal collocation numerical technique to solve the "partial differential equations describing the mass transfer to a RRDE" 6 in absence of any ionic migration.…”

“…3 He also stated that collection efficiency falls with increasing gap thickness for both presence and absence of ionic migration cases. 3 Parikh et al 6 used orthogonal collocation numerical technique to solve the "partial differential equations describing the mass transfer to a RRDE" 6 in absence of any ionic migration. Newman 7 evaluated the effect of ionic migration on limiting currents for a RDE system, a growing mercury drop system, a semi-infinite stagnant fluid system, and a Nernst diffusion layer system.…”

“…Collection efficiency is defined as the "ratio of amount of material detected at the ring to the amount produced at the disk. 3 " The transit time indicates the average time required for material produced at the disk electrode to travel across the gap between the disk and the ring electrode. 4 The transit time depends on the radius of the disk electrode, inner radius of the ring electrode, angular velocity of rotation of the RRDE, kinematic viscosity of the solution and diffusivity of the species generated at the disk electrode.…”

Quantitative Kinetic Analysis of a PdAu3Alloy Catalyst for Oxygen Electro-Reduction

“…It becomes apparent that the overpotential of the oxygen reduction at larger current densities is rather high. The hydrogen peroxide current efficiency H PC E is calculated using the following equation taken from the dissertation of I. Herrmann (FU Berlin) 40 H PC E = 100 × 2I r I r + N ex p I d [28] with the HC P E values obtained in percent.…”

“…In a more recent work on RRDE simulations, Guha investigated the effect of the supporting electrolyte. 28 Moreover, micro-turbulences due to surface roughness of the catalyst layer on the disk electrode can also affect the system. The instability to the steady-state solution for the flow velocity field introduced by roughness was analyzed in Ref.…”