Controlled Assembly of Bimetallic PtRh-Modified Tin Oxide Hollow Nanotubes with High Sensing Activity for Ultrasensitive Formaldehyde Detection

Gas sensors for rapid identification of formaldehyde (HCHO) exposure risks are of great significance, given the volatility, toxicity, and near-imperceptibility of HCHO. However, the precise design of highly reactive sensing materials remains a substantial challenge that limits the application of gas sensors. Here, PtRh-modified tin oxide (PtRh/SnO₂) hollow nanotubes with an open hollow nanostructure and bimetallic sensitization are proposed for regulating the reactivity to achieve ideal improvement in HCHO-sensing performance. The prepared 1.5% PtRh/SnO₂ hollow nanotube-based sensor achieves a high sensing response (R_a/R_g = 265.8-25 ppm of HCHO), fast response and recovery rate (2.6 and 6.1 s), good selectivity, and strong anti-interference toward HCHO at 200 °C. Based on the ex/in situ characterizations and density functional theory (DFT) calculations, the enhanced sensing properties are mainly attributed to the construction of hierarchical hollow nanostructures providing sufficient active sites for gas absorption, as well as the oxygen spillover effect from Pt, the catalytic property of Rh, and their synergistic effects. Hence, the architecture demonstrates enhanced adsorption capacity and interfacial reactivity toward HCHO, thereby improving the sensing response and selectivity. In addition, the PtRh/SnO₂ sensor was used to monitor the HCHO in oysters, providing promising applications in real-time aquatic product HCHO monitoring.