Dual-Active-Site Synergy in Metal-Organic Framework-Derived Er:CeO2/ZnO Nanofibers Enabling Humidity-Independent...

The development of gas sensors that combine high sensitivity and selectivity with stable operation at room temperature under high humidity remains a pivotal challenge for reliable breath analysis. This work presents a rational design and facile synthesis of three-dimensional hierarchical beaded Er3+-doped CeO2/ZnO (Er:CeO2-ZnO) heterojunction nanofibers (NFs) via a ZIF-8-templated electrospinning strategy. This integrated approach converges multiple material design principles. It employs a ZIF-8-derived porous ZnO scaffold for enhanced gas accessibility, in situ formed n-n heterojunctions for efficient charge separation, and Er3+-induced oxygen vacancies in CeO2 for optimized surface chemistry. Comprehensive characterization confirms the successful integration of these components and the creation of abundant active sites. The optimized sensor exhibits exceptional room-temperature triethylamine (TEA) sensing performance, including a high response, a low detection limit (56 ppb), fast response/recovery kinetics (16 s/58 s to 10 ppm TEA), and excellent selectivity. Remarkably, the sensor demonstrates outstanding long-term stability (over 120 days) and humidity-independent performance across a wide relative humidity range (25-90% RH). Kinetic analysis of the sensing transients reveals biphasic behavior, providing direct evidence for a dual-active-site synergistic mechanism involving oxygen vacancy-rich regions for gas adsorption/activation and heterojunction interfaces for charge separation. Furthermore, a dynamic self-refreshing mechanism is proposed to elucidate the exceptional humidity tolerance. This work provides fundamental insights into the design of multifunctional sensing materials and presents a highly promising candidate for reliable gas detection in complex, humid environments such as exhaled breath analysis.