Voltage polarity relay-optimal control of electrochemical urea oxidation (hemodialysis application)

Voltage polarity relay (VPR) is shown to optimize the urea oxidation rate and urea current utilization under constant current conditions in direct electrochemical urea oxidation. Direct electrochemical urea oxidation is characterized by reversible deactivation of the working electrode due to oxidation products remaining on the surface and the requirement that the working electrode potential remain below about 1.1 V relative to Ag/AgCl to prevent undesirable secondary electrochemical oxidations. The VPR method monitors the potential of the working electrode relative to a suitable reference and changes system polarity when the upper potential set limit is reached. Thus. what was the working electrode becomes the counter electrode and vice versa. Since urea oxidation products are desorbed from the counter electrode when its potential drops below about -0.6 V relative to Ag/AgCl, alternating electrode functions between working and counter provides cyclic electrode regeneration and continuous urea oxidation.