Biomorphic WO3@WS2 heterojunction composites for enhanced NO2 gas-sensing performance at room temperature

The fabrication of heterojunction composites with high activity is an effective way to enhance the room tem-perature (RT) gas sensing performance. However, it is still challenging for a well-designed heterojunction interface to obtain more excellent sensitivity and response-recovery rate. Herein, the hemp sticks derived from porous carbon were used as bio-templates. WO3@WS2 heterojunction composites with bio-morphology were synthesized via hydrothermal and sulfur vapor transmission methods. 3D hierarchical structure, exposed the S-termination of WS2, and the "S-W-O" of heterojunction interface WO3@WS2 collectively enhance the WO3@WS2/BC gas sensing performance. The results showed that the WO3@WS2/BC composite sensor exhibited remarkable selectivity to NO2 and reached a response as high as 42.9 toward 100 ppm NO2 at RT, about 3-fold higher than that of pristine WS2 nanosheets, a super-fast response/recovery time (1.6 s/37 s). The WO3@WS2/BC sensor maintained its excellent performance within twelve cycles and three months of storage in air, which has good selectivity for NO2 gas. This study provides a new line of research for developing highly sensitive NO2 detection at RT.