A hydrogen peroxide microelectrode to use in bioelectrochemical systems
By Erhan Atci and Jerome T. Babauta and Haluk Beyenal
Published in Sensors and Actuators B: Chemical
2016
Abstract
Polarized electrodes are used in bioelectrochemical systems (BES) in which the electrodes are used to grow biofilms or remove biofilms. In either case \H2O2\ is generated as an intermittent product of oxygen reduction. Traditionally, a \H2O2\ microelectrode (HPM) consists of a sealed platinum wire with a tip a few ?m in diameter. This microelectrode is connected to an external reference electrode (which is also used as the counter electrode) and polarized to +0.8 VAg/AgCl to measure \H2O2\ concentration. This traditional \H2O2\ microelectrode (tHPM) works well for measuring \H2O2\ concentrations in biofilms growing on non-polarized surfaces. It is a common misconception that this tHPM will work correctly in an electric field. We observed experimentally that the tHPM produces artifacts in measurements when it is used in BES. This has not been noticed before. These undesired effects needed to be resolved before \H2O2\ concentration could be measured in BES. The goals of this work were to (1) describe the artifacts related to the use of tHPM in BES, (2) develop a \H2O2\ microelectrode which does not suffer from these artifacts, (3) verify the operation of the new microelectrode in BES, and (4) improve the sensitivity of the microelectrode. In this work, we built an all-in-one \HPM\ (aHPM) in which the reference electrode and the working electrode were placed a few 100 ?m away from each other in a sealed configuration. We verified that our aHPM, unlike the tHPM, is not affected by an interfering electric field and generates reproducible, correct measurements in BES. We compared \H2O2\ flux measurements from the electrode in a \BES\ with depth profiles measured using aHPM and tHPM to identify artifacts and reliability. Finally, after proving the reliability of the aHPM in BES, we improved its sensitivity. The aHPM demonstrated a linear calibration in the range of 0.87 ?M to 166.8 ?M \H2O2\ concentration with a 1.69 ?M limit of detection (S/N = 2). Although our goal was to develop an \HPM\ which can operate in an electric field, the developed microelectrode can be used in many other applications requiring ?M resolution.