Review—Recent Advances in Electrochemical Impedance Spectroscopy Based Toxic Gas Sensors Using Semiconducting Metal Oxides

Abstract

Electrochemical Impedance Spectroscopy (EIS) in the past few years has been used to design gas sensors. EIS based gas sensing has been considered as an ultra-sensitive technique to identify and measure different toxic gases. Their sensing performance has been superior when compared to other conventional techniques. Impedance makes it possible to investigate the finer changes occurring on the surface of sensing layers leading to the identification of the target gases such as H2S. The measurements are carried out by scanning the electrode surface with a mixture of frequencies from 1 Hz to 10 MHz and recording the response as Nyquist and Bode plots. From these plots, the results can be used to elucidate the electrochemical phenomena. The acquired impedance data can be fitted into equivalent circuits and this is further modeled to obtain information about the interfacial phenomena like grain bulk resistance, grain boundary resistance, interface between electrode and sensing film resistance. These phenomena support the sensing of toxic gases from ppm - ppb level. This article focuses on impedance spectroscopy and its relevance to sensors, challenges in detecting toxic gases on the electrode surfaces prepared using semiconducting metal oxides, doped metal oxides and graphene based composites along with the research gaps, current innovations and future directions. EIS based gas sensors have high selectivity, sensitivity, reproducibility, long term stability and they also assist prediction of the electrochemical mechanisms for the analyte gases.

Recent advances in cellulose-based membranes for their sensing applications

“…According to different physical, chemical and electronic mechanisms, gas sensors can be divided into semiconductor metal oxide sensors, electrochemical sensors, optical sensors, catalytic combustion sensors, etc. Semiconductor metal oxide materials have become the most promising gas sensors because of their low cost, convenient operation, fast response and high sensitivity for target gases detection (Balasubramani 2020 ). Besides, electrochemical gas sensors work with the measured gas and then output the electrical signal proportional to the gas concentrations.…”

Capacitive-Coupling Impedance Spectroscopy Using a Non-Sinusoidal Oscillator and Discrete-Time Fourier Transform: An Introductory Study

“…In Equations (6) and 8, the negative frequency component (k < 0) is a complex conjugate of the positive frequency component:…”

“…EIS is used to analyze the characteristics of fuel cells, lithium-ion batteries, and photovoltaic cells [1][2][3][4][5]. It is often used to analyze the response mechanism of chemical sensors and detect response signals in them [6][7][8]. In general, the ionic conduction speed differs in electrode interfaces and the electrolytes of fuel cells and lithium-ion batteries.…”

Quality‐Indicator‐Based Preprocessing for the Distribution of Relaxation Times Method

“…It can be used for detailed characterizations because of its non-invasive nature and the ability to detect and distinguish different physicalchemical processes based on their characteristic time constants and therefore finds application in various systems. [1][2][3][4] The impedance behavior of an electrochemical system can be described by an equivalent electrical circuit (EEC), representing the entirety of its physical-chemical processes. [5][6][7] To quantify all processes within the impedance spectrum, this model is fitted to the measured data.…”