Improved Gas-Sensitive Properties by a Heterojunction of Hollow Porous Carbon Microtubes Derived from Sycamore Fibers

Sycamore villus fibers were used to prepare hollow and porous carbon microtubes (CMTs) and the ZnO/CMT composite with heterojunctions by simple carbonization for the first time. Because the hollow and porous structure provided more channels to facilitate the adsorption and desorption of gas molecules, both CMTs and ZnO/CMT exhibited higher sensitivity and quicker response (<16 s) to and recovery (<2 s) from multiple target analytes. Furthermore, ZnO nanoparticles were uniformly dispersed on the CMTs by zinc acetate-assisted carbonization, which avoided the agglomeration of ZnO and formed a large number of heterojunctions, greatly improving the sensitivity of ZnO/CMT. In comparison to the pure CMTs and ZnO, the response of ZnO/CMT to the four target gases increased by 1.4∼4.3 and 9.9∼18.1 times, respectively. Their limit of detection for NH3 was calculated as 62.5 and 8.8 ppb, respectively. After 30 days, the responses of CMTs and ZnO/CMTs to 500 ppm NH3 decreased by 9.4 and 6.5%, respectively. This indicated that CMTs and ZnO/CMT had high sensitivity and good long-term stability. This study provides a feasible way for the gas-sensing application of biomass carbon materials with heterojunction structures.