Vitalizing Perovskite Oxide-Based Acetone Sensors with Metal-Organic Framework-Derived Heterogeneous Oxide Catalysts

Perovskite oxides are promising candidates for chemiresistive-type gas sensors owing to their exceptional thermal and chemical stability during solid-gas reactions. However, perovskites suffer from critical issues such as low surface area and poor surface activity, which negatively influence the sensing characteristics. While metal nanoparticles can be incorporated in perovskites to improve their reactivity, the fundamental incompatibility between catalytic metals and perovskite oxides often leads to substantial structural degradation as well as phase instability. Herein, we overcome this challenge through the introduction of an intermediary phase that forms coherent interfaces with both the perovskite phase and catalyst metals. Specifically, we present the case study of p-type La_0.8Ca_0.2Fe_0.98Pt_0.02O₃ perovskite, whose hole accumulation layer was modulated by the incorporation of metal-organic framework (MOF)-derived n-type α-Fe₂O₃ nanoparticles decorated with highly dispersed Pt catalysts. The resulting composite exhibited significantly improved surface activity over the nonmodified La_0.8Ca_0.2FeO₃ perovskite, leading to exceptional chemiresistive sensing performance toward acetone gas (R_g/R_a = 39.8 toward 10 ppm of acetone at 250 °C) with high cross-sensitivity against interfering gases. Importantly, our findings reaffirm the critical influence of interfacial engineering in facilitating surface chemical reactions on perovskite oxides and, by doing so, effectively provide a general synthetic guideline to the design of perovskite-based chemiresistors.