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Surface conductivity of binary carbonate as a performance-governing parameter of an electrochemical CO2 gas sensor
Bulletin of Materials Science ( IF 1.8 ) Pub Date : 2021-08-26 , DOI: 10.1007/s12034-021-02526-y
Prashant Ambekar 1 , Jasmirkaur Randhawa 2
Affiliation  

In electrochemical CO2 gas sensor, the chemical potential of electrolyte changes on adsorption of CO2 molecules as the process involves catalytic electron transfer. In addition, it is the rate-determining step that decides sensor’s response. In this study, in-situ bulk AC, DC and surface electronic conductivities of CaCO3 + Li2CO3 binary solid electrolyte were investigated at different temperatures and CO2 gas partial pressures using complex impedance spectroscopy, Wagner’s DC polarization technique and four-probe method, respectively. For the four-probe conductivity measurements with crucial requirement of high temperatures and test gas variations, a customized sample holder was designed and fabricated having gold-plated equidistant, spring-loaded electrodes and localized heating system (maximum 593 K). The AC bulk conductivity was found to decrease with rise in CO2 gas concentration (from 0.1 to 100%) by about two orders and one order of magnitudes at lower and higher temperatures, respectively. Similarly, surface conductivity variation with temperature also showed Arrhenius behaviour for both the concentrations of CO2 viz. 0.04 and 10%, giving lower value of activation enthalpy for lower CO2 concentration. The surface conductivity change in the presence of different concentrations of CO2 gas is justified by comparing with AC bulk conductivity measurements at different CO2 partial pressures and DC conductivity along with sensing response. The mechanism is explained using activated charge transfer data. The range of Ea values on adsorption of CO2 gas was found to be in the electronic excitation window, suggesting involvement of a new parameter to be investigated for non-Nernstian response of EC sensors.



中文翻译:

二元碳酸盐的表面电导率作为电化学 CO2 气体传感器的性能控制参数

在电化学 CO 2气体传感器中,电解质的化学势随着 CO 2分子的吸附而变化,因为该过程涉及催化电子转移。此外,决定传感器响应的是速率决定步骤。在本研究中,研究了 CaCO 3 + Li 2 CO 3二元固体电解质在不同温度和 CO 2的原位体 AC、DC 和表面电子电导率分别使用复阻抗谱、Wagner 的直流极化技术和四探针法测量气体分压。对于对高温和测试气体变化有关键要求的四探针电导率测量,设计和制造了一个定制的样品架,具有镀金等距、弹簧加载电极和局部加热系统(最大 593 K)。发现 AC 体电导率随着 CO 2气体浓度(从 0.1% 到 100%)的增加而分别在较低和较高温度下降低约两个数量级和一个数量级。同样,表面电导率随温度的变化也显示出两种 CO 2浓度的阿伦尼乌斯行为即。0.04 和 10%,对于较低的 CO 2浓度给出较低的活化焓值。通过与不同 CO 2分压和直流电导率下的交流电导率测量值以及传感响应进行比较,可以证明在不同浓度 CO 2气体存在下的表面电导率变化是合理的。使用激活的电荷转移数据来解释该机制。发现CO 2气体吸附的E a值的范围在电子激发窗口内,表明涉及要研究EC传感器的非能斯脱响应的新参数。

更新日期:2021-08-26
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