Editors' Choice - Review - Solid-State Electrochemical Carbon Dioxide Sensors: Fundamentals, Materials and Applications

The recent series of global catastrophic events (e.g., heatwaves, flooding) have again raised the concerns over the greater impact of climate change. The focus has been concentrated towards reducing CO₂ emissions from fossil fuel based energy systems. It is necessary to build a commercially viable CO₂ sensor with high reliability. The gas-sensing field has shifted from using a cumbersome gas-reference electrode to solid-state electrochemical devices because they can be employed to detect CO₂ in real-time overcoming the limits of widely used IR-based CO₂ sensors. Here, solid electrolytes and mixed conducting semiconductor-based gas sensors for various gaseous species including CO₂ are reviewed. The study on semiconducting metal oxides (SMOs) has been pushed forward as a most viable option for commercializing monolithic all-solid-state electrochemical gas sensors. Among SMOs, the perovskite-type metal oxides are considered as one of the promising structures for next-generation greenhouse gas sensors due to their remarkable thermal and chemical stability. This article also includes the fundamental understanding of essential factors that govern the electrical signals in all-solid-state electrochemical gas sensors.