Adjustable p‐n transition behavior based on MoO3‐decorated hollow α‐Fe2O3 for highly hydrogen‐selective sensors

Summary Hydrogen sensing is very important in terms of its explosive and flammable effects on human health and industrial production. However, achieving trace level detection of H2 with high selectivity, fast response, and good sensitivity at high temperatures remains a challenge. In this work, MoO3‐decorated three‐dimensional hollow α‐Fe2O3 nanoboxes were obtained using a simple wet‐chemical method, which evolved from Prussian blue as a template. Phase and structure analyses confirmed that MoO3 was successfully scattered on the α‐Fe2O3 nanoboxes surface. The gas sensor fabricated using the MoO3/α‐Fe2O3‐1 hollow nanoboxes shows exclusive H2 sensing properties with n‐type and p‐type sensing response to CO, together with a fast response/recovery time at 300°C. The abnormal sensing characteristic is associated with the change in the potential barrier height due to the heterojunction‐structure formation of MoO3 and α‐Fe2O3. This work provides a general approach for tuning the sensing selectivity of gas sensors via the modulation of potential barrier heights in p‐n heterojunctions. The synthesis process of MoO3/α‐Fe2O3‐1 and its response value towards 5 ppm H2 and CO.