Grain boundary-induced drastic sensing performance enhancement of Fe₂O₃ gas sensors for acetone

Exploring the structure–activity relationship between the performance of gas sensors and the structure of semiconductor metal oxide (SMO) nanomaterials is crucial for understanding and designing gas-sensing materials and overcoming the application limitations of SMO-based gas sensors. Regulation of a single SMO microstructure provides a promising solution to address this scientific problem due to its controllable composition. In this study, we control the grain boundary (GB) density of Fe₂O₃ nanomaterials using a simple solvothermal method. They have similar chemical compositions and crystal phases, providing an ideal platform for studying the influence of the GB density on the gas-sensing performance. Gas-sensing tests showed that the Fe₂O₃-1 sensor with medium GB density and the Fe₂O₃-2 sensor with high GB density had higher sensitivity and selectivity than the Fe₂O₃-0 sensors with low GB density before reaching the optimal operating temperature. However, when the GB density increased, the response to acetone decreased slightly, whereas the optimal operating temperature decreased. This work highlights the unique performance of the GB density in enhancing the gas sensitivity of a single SMO.