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 H 2 with high selectivity, fast response, and good sensitivity at high temperatures remains a challenge. In this work, MoO 3 ‐decorated three‐dimensional hollow α‐Fe 2 O 3 nanoboxes were obtained using a simple wet‐chemical method, which evolved from Prussian blue as a template. Phase and structure analyses confirmed that MoO 3 was successfully scattered on the α‐Fe 2 O 3 nanoboxes surface. The gas sensor fabricated using the MoO 3 /α‐Fe 2 O 3 ‐1 hollow nanoboxes shows exclusive H 2 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 MoO 3 and α‐Fe 2 O 3 . 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.