USE OF MULTIPLE ELECTRODES TO PROVIDE UNIFORM POTENTIAL DISTRIBUTION DURING CONTROLLED POTENTIAL ELECTROLYSIS

In practice, the size of a single working electrode in controlled pote ntial electrolysis cells can be extended in only two dimensions while maintaining uniform potential distribution. A previously published the oretical model predicted that working electrode dimensions in controll ed potential electrolysis cells could be effectively extended in three directions while maintaining uniform potential distribution by utiliz ing several working electrodes interconnected with appropriately chose n external resistors. A controlled potential electrolysis cell utilizi ng three working electrodes placed at successively increasing distance s along the current path from the counter electrode has been designed and tested. The electrodes were connected in either series or parallel with external compensating resistors calculated according to theory. Nearly identical interfacial potentials were observed for all three el ectrodes, with dramatic reduction of the potential errors observed wit hout the use of the external resistors. It was further demonstrated th at if optimum placement of the reference electrode did not pertain, th en the multiple electrode/external resistance network behaved as a sin gle electrode operating with a single uncompensated solution resistanc e. This should facilitate the use of conventional positive feedback te chniques to minimize. potential control errors. Because changes in cel l geometry or solution require different sets of compensating resistor s, two operational amplifier-based circuits which eliminate this incon venience were designed and tested. The circuits employ comparison of e ither individual electrode currents or potentials and feedback control to maintain these at identical values.