Synthesis of Ce-Doped ZIF-8-Derived Core–Shell ZnO Sensors via Double Sintering for Highly Sensitive Formaldehyde Detection at Room Temperature

Formaldehyde, a common indoor air pollutant, poses a serious threat to human health. Therefore, there is an urgent need to develop highly selective and sensitive formaldehyde gas sensors that operate at room temperature. Doping with rare-earth elements is an effectively proven strategy for optimizing the gas-sensing performance at room temperature. This study developed a method to modify ZnO derived from ZIF-8 by doping it with the rare-earth element cerium (Ce). The Ce-doped ZnO (ZCO) series of sensors inherit the shell-and-core architecture derived from the ZIF-8 precursor, featuring a high specific surface area that provides support for gas-sensing reactions. Additionally, Ce doping induces the formation of more oxygen vacancies, thereby enhancing the formaldehyde adsorption. Among these, the ZCO-2 gas sensor exhibits the best formaldehyde sensing properties at room temperature, with a responsiveness of 1006 for 500 ppm formaldehyde (77.4 times that of a pure ZnO gas sensor) and a response/recovery time of 9/3 s. Because of the high response value, fast response/recovery time, excellent selectivity, repeatability, and stability of this gas sensor, it has a very promising prospect in practical applications.