Department of Electrical Engineering and Computer Science , Michigan State University , East Lansing , Michigan 48824 , United States.
ACS Sens. 2018 Jun 22;3(6):1126-1134. doi: 10.1021/acssensors.8b00155. Epub 2018 Jun 4.
Electrochemical amperometric sensors require a constant or varying potential at the working electrode that drives redox reactions of the analyte for detection. The interfacial redox reaction(s) can result in the formation of new chemical products that could change the initial condition of the electrode/electrolyte interface. If the products are not inert and/or cannot be removed from the system such that the initial condition of the electrode/electrolyte interface cannot be restored, the sensor signal baseline would consequently drift, which is problematic for the continuous and real-time sensors. By setting the electrode potential with the periodical ON-OFF mode, electrolysis can be forestalled during the off mode which can minimize the sensor signal baseline drift and reduce the power consumption of the sensor. However, it is known that the relaxation of the structure in the electrical double layer at the ionic liquid/electrode interface to the steps of the electrode potential is slow. This work characterized the electrode/electrolyte interfacial relaxation process of an ionic liquid based electrochemical gas (IL-EG) sensor by performing multiple potential step experiments in which the potential is stepped from an open circuit potential (OCP) to the amperometric sensing potential at various frequencies with different time periods. Our results showed that by shortening the sensing period as well as extending the idle period (i.e., enlarge the ratio of idle period versus sensing period) of the potential step experiments, the electrode/electrolyte interface is prone to relax to its original state, and thus reduces the baseline drift. Additionally, the high viscosity of the ionic liquids is beneficial for electrochemical regeneration via the implementation of a conditioning step at zero volts at the electrode/electrolyte. By setting the working electrode at zero volts instead of OCP, our results showed that it could further minimize the baseline drift, enhance the sensing signal stability, and extend the functioning lifetime of a continuous IL-EG oxygen sensor.
电化学安培传感器需要在工作电极上施加恒定或变化的电势,以驱动分析物的氧化还原反应进行检测。界面氧化还原反应会导致新化学产物的形成,这些产物可能会改变电极/电解质界面的初始状态。如果产物不是惰性的,并且/或者不能从系统中去除,使得电极/电解质界面的初始状态无法恢复,则传感器信号基线会随之漂移,这对连续和实时传感器来说是一个问题。通过周期性地将电极电位设置为 ON-OFF 模式,可以在 OFF 模式下阻止电解,从而最大限度地减少传感器信号基线漂移并降低传感器的功耗。然而,众所周知,在离子液体/电极界面处双电层的结构弛豫到电极电位的步骤是缓慢的。通过在不同频率下以不同的时间段将电位从开路电位(OCP)跃变到安培检测电位,执行多次电位跃变实验,本工作表征了基于离子液体的电化学气体(IL-EG)传感器的电极/电解质界面弛豫过程。我们的结果表明,通过缩短检测周期以及延长电位跃变实验的空闲周期(即增大空闲周期与检测周期的比值),电极/电解质界面更容易恢复到原始状态,从而减少基线漂移。此外,离子液体的高粘度有利于通过在电极/电解质处实施零伏的调理步骤进行电化学再生。通过将工作电极设置为零伏而不是 OCP,我们的结果表明,它还可以进一步最小化基线漂移,增强传感信号稳定性,并延长连续 IL-EG 氧传感器的工作寿命。