Chemiresistive gas sensors: From novel gas-sensing materials to electrode structure

Gas sensors based on chemiresistive technology are attractive for their small size, low-cost fabrication, predictable electrical properties, and compatibility with electronic circuits. They have various applications from health and safety to energy efficiency and emissions monitoring. Despite exploring many gas-sensing materials to detect different gases for the above-mentioned applications, these sensors have limitations such as poor selectivity, high limit of detection, poor reversibility, high operating temperature, and poor stability that restrict their implementation in real-time applications. To address these limitations and improve the sensing performance toward target gases, various approaches have been developed. In this regard, an important aspect to improve the gas-sensing performance is to optimize the device architecture by selecting the appropriate gas-sensing material, electrode material, and electrode structure design. This review discusses the advancements in the novel gas-sensing materials, such as metal-organic frameworks (MOFs), MXenes, graphitic carbon nitride (g-C3N4), hexagonal boron nitride (h-BN), group III–VI semiconductors, phosphorene, black phosphorus, metal ferrites, and high entropy oxides. In addition, this review discusses the impact of various electrode materials, including platinum (Pt), gold (Au), silver (Ag), chromium (Cr), indium tin oxide (ITO), and aluminum (Al), and its electrode structures and design parameters on the gas-sensing performance. The electrode structures covered in this review are head-to-head, interdigitated, fractal, and laser-induced graphene. Finally, this review highlights the summary, challenges, and future perspectives of novel gas-sensing materials, electrode materials, and their structures to improve the gas-sensing performance of chemiresistive sensors.