Advances in Perovskite Oxides for Chemiresistive Sensors

Perovskite oxides (PO) possess a crystal structure known as ABO3, where rare-earth metal atoms occupy the A sites, transition metal atoms are found at the B sites, and oxygen is the anion. Elements from nearly 90% of the periodic table can occupy A or B sites, resulting in various crystal structures and compositions within the PO family. Due to this flexibility, PO exhibits outstanding physicochemical and electronic properties, such as high oxygen ion conductivity and excellent redox reaction characteristics. Additionally, their ability to be synthesized at high temperatures contributes to their superior thermal and chemical stability, enabling widespread use in applications such as electrocatalysis-based energy storage and chemical looping combustion. Recently, the fourth industrial revolution and advancements in nanomaterials have amplified the importance of gas-sensing technology in environmental monitoring, industrial safety, and healthcare. Therefore, extensive research in gas sensors highlights the development of highly sensitive, selective, and stable sensors.PO-based chemiresistive sensors have attracted significant attention due to their ability to tailor the chemical structures of active sites for selective gas reaction, control the amount of oxygen adsorption, and offer a reliable sensing performance. However, enhancing the sensing performance of PO-based sensors faces challenges due to the low intrinsic surface activity of p-type PO. Various efforts to overcome this limitation include nanostructure engineering to increase the surface area and porosity of PO, compositional modulation, such as partial substitutions, and the formation of heterostructures. Moreover, functionalizing PO as catalysts onto sensing layers can enhance sensing performance by influencing the adsorption/desorption kinetics of the target gas, making it a promising approach.In this Account, we delve into versatile methodologies for maximizing gas sensing performance using the p-type PO, highlighting key advancements within our research group. Beginning with explaining operation mechanisms and essential design factors of chemiresistive sensors based on PO, various strategies are introduced, each tailored to specific roles in chemiresistive sensors, including the sensing layer, reaction promoter, and supports for the catalysts. These include electrospinning to control the PO morphology and the galvanic replacement reaction on PO for simultaneous changes in the morphology and composition of PO sensing layers. Additionally, the enhanced surface activity achieved by loading catalytic PO particles on sensing layers and the latest technologies involving ex-solution and single-atom catalysts on PO are discussed. Finally, this Account concludes with a summary and a discussion of the remaining challenges and future tasks, providing in-depth insights into PO-based chemiresistive sensors.