Strategies to boost chemiresistive sensing performance of In₂O₃-based gas sensors: an overview

The development of effective and efficient materials for the selective and sensitive detection of toxic gases and volatile organic compounds is crucial for protecting human health and the environment. In this respect, a well-known n-type semiconducting material, namely indium oxide (In2O3), has attracted significant attention because of its gas-sensing applications. The rapid advances in various synthesis techniques have enabled researchers to explore numerous novel nanostructures and their integration into smart gas-sensing devices. Despite sustainable development, the application of In2O3 in gas sensing is limited by its poor selectivity, high working temperature, and response deterioration under humid conditions. This review outlines various strategies, such as morphology and interface engineering, catalytic functionalization, shell structure and thickness, and doping, for improving the gas detection performance of In2O3-based chemiresistive gas sensors. The significant influence of the nanostructures with different morphologies on the gas-sensing performance of In2O3-based sensors is also demonstrated. Pristine In2O3 nanomaterials with zero-dimensional (0D) to three-dimensional (3D) morphologies are reviewed. Different composites of In2O3, including In2O3/metal oxides (p-type and n-type), In2O3/noble metal loading and encapsulation, In2O3/elemental doping, In2O3/conducting polymers, and In2O3/carbonaceous materials, were evaluated to improve their sensing performances. Finally, a future outlook on the further progress of the In2O3 gas sensors is suggested.