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Abstract Gas sensors based on metal oxides have attracted wide attention, due to their inherent advantages such as low cost, small size, fast response, and easy usage. Recently, much effort have been put into the design of metal oxide‐based sensing materials to further improve the performance of gas sensors. Among them, the fabrication of hierarchical metal oxide‐based sensing materials has become the most attractive strategy. In this article, the authors widely review the last decade of development of hierarchical metal oxide‐based gas sensors, in which several representative gases including formaldehyde, acetone, H 2 S, amines, and water are chosen as the analytes to discuss in depth. The application fields cover indoor air quality monitoring, breath analysis, and food quality and safety. The research advances for each gas is summarized from the perspective of excellent sensing performance in terms of low operating temperature and detection limit, high selectivity, fast responses, and humidity independent responses. Furthermore, the accepted sensing mechanism of metal oxide‐based gas sensors and widely used technology to verify these mechanisms are both included. Finally, the outlook and challenges for future investigations of hierarchical metal oxide‐based gas sensors are also discussed from the perspectives of theory and practice.
Yu et al. (Sun,) studied this question.