Controlling the Crystal Phase Structure of WO₃ Nanosheet-Based Hierarchical Spheres for Enhanced Gas Sensing Performance

The pursuit of high performance is the eternal theme in gas sensor research. Because of the complexity of the response and recovery processes, the selective detection, high response, rapid response, and recovery remain challenging in the atmospheric environment. In this paper, WO3 hierarchical spheres (WO3 HS) with different crystalline phase ratios are successfully synthesized to evaluate the relationship between the phase structure and gas-sensitive properties. The as-prepared WO3-2 HS samples achieve superior gas sensing characteristics including high response (S = 24.2) and fast response and recovery speed (1 and 19 s) to 100 ppm acetone at 300 °C. The superior acetone sensing performance probably originates from the regulation of the phase ratios of nanosheet-based WO3. With the decrease of orthorhombic phase and the increase of monoclinic phase, the specificity detection to acetone is increased significantly. The reasons for such a huge selectivity change are discussed in detail. From the perspective of reaction kinetics, we also compare the contributions of specific surface area and crystalline phase impacting the gas sensing performance.