Formaldehyde gas sensors based on SnO2/ZSM-5 zeolite composite nanofibers

Highlights: • Highly dispersed of electrospun SnO₂/ZSM-5 composite nanofibers are synthesized to fabricate formaldehyde sensor. • The SnO₂/ZSM-5 composite nanofibers sensor performs a high selectivity to formaldehyde. • The SnO₂/ZSM-5 sensor shows a strong anti-interference ability. • More oxygen vacancies exist on the surface of the composite which increase the content of adsorbed oxygen. • The heterogeneous structure of SnO₂/zeolite increase the charge transfer between the interfaces. -- Abstract: An additional layer of zeolite on the surface of metal oxides results in an increased selectivity as gas sensors. However, there is insufficient knowledge on how interactions between the zeolite and gas-sensitive materials improve gas sensing properties. To increase the area of the interface between the materials and decrease agglomeration, SnO₂/ZSM-5 composite nanofibers were synthesized via an electrospinning technique. "Bone joints," such as ZSM-5 nanoparticles, were present in the composite nanofibers. Analyses of the gas sensing properties show that the selectivity and sensitivity of the sensors to formaldehyde were improved. Electronic surface states and charge transport properties were measured via X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS), respectively. It was inferred from the XPS results that the adsorbed oxygen on the surface of the composite increased considerably, thus improving the sensitivity of the sensors. The results of the EIS and electrical equivalent circuits indicate that the interface of the two materials plays a significant role. A larger interfacial area between the zeolite and SnO₂ can increase electron transfer and enhance the sensitivity and selectivity of the sensors. This study provides a strategy to improve the sensing properties of semiconducting metal oxide gas sensors.