DESIGN OF A WALL-JET ELECTRODE REACTOR AND ITS APPLICATION TO THE STUDY OF ELECTRODE REACTION MECHANIAMS

摘要

For our research into the mechanism of the a.c. electrolytic graining of rolled aluminium substrates, we designed a suitable wall-jet electrode reactor and developed a numerical computational procedure to solve the mass transport problems involved in using the reactor in a quantitative electrochemical study of this controlled corrosion process. The reactor is evaluated by means of mass-transport-limited current measurements using as a model reaction the reduction of ferricyanide ions at a platinum electrode surface from a 0.01 M K_3Fe(CN)_6 - 0.01 M K_4Fe(CN)_6 solution containing 1 M KC1 as supporting electrolyte. The dependence of the mass-transport-limited current on the crucial reactor parameters - volume flow rate Vf, the nozzle diameter a and the radius of the electrode R - is established and verified with theoretical predictions. The reactor is shown to have the desired wall-jet hydrodynamics for: 1.6 X 10~(-6) < = V_f < 4.3 X 10~(-6) m~3 s~(-1),1.5 < = a < = 3 mm and 15 < = R < = 20 mm. The computational method is based on a second-order-correct implicit finite difference approach and the co-ordinate transformation making a simple Cartesian space discretization compatible with efficient computing, thus allowing the computations to be performed on a personal computer. The numerical scheme used, is demonstrated through calculation of a single step chronoamperometric transient for a simple one electron transfer reaction and shown to be accurate by comparing the computed with experimentally determined current transients using the model reaction mentioned above.