An investigation of the factors influencing stability in continuously‐powered screen‐printed amperometric dissolved oxygen sensors

The continuously powered response of dissolved oxygen sensors fabricated as screen printed devices has been investigated. A reduction in the sensitivity of these devices has been observed when they are continuously powered at potentials of –0.6V versus Ag/AgCl reference electrodes. Periodically recorded voltammograms have indicated that the reduction in sensitivity can be attributed to a build up of hydroxyl ions beneath the sensor membrane that inhibits oxygen reduction. It has been found that powering these devices at more negative potentials mitigates against the decrease in sensitivity but results in a slowly increasing sensitivity. This is attributed to an increase in the effective area of the working electrode resulting mainly from leakage through the waterproofing layer covering the electrode interconnects.