Crystalline Nanodiamond-Induced Formation of Carbon Nanotubes for Stable Hydrogen Sensing

Herein, multiwalled carbon nanotubes (MWCNTs) were synthesized through a two-step chemical vapor deposition process via an ultra-nanocrystalline diamond (ND) as a carbon source for the first time, and no gaseous carbon molecules were used during CNT growth. A unique core–shell-like morphology was revealed from the high-resolution transmission electron microscopy (HRTEM) microstructure in which the CNT is covered by nanodiamond grain boundaries. The NDCNT is then fabricated with a metal interdigitated electrode to form hydrogen sensors. The as-fabricated NCDNT exhibits a higher gas sensor response toward H2 gas than the as-fabricated ND films. Moreover, the present NDCNT sensor shows rapid response/recovery during the H2 adsorption/desorption process and shows high selectivity. It also exhibits long-term stability and repeatability over 2 months without perceptible degradation. This can be attributed to the present NDCNT structure that has defect sites from nanodiamond grains and contributes numerous binding sites for the H2 gas molecules. The present sensor shows rapid recovery compared with previously reported studies due to the H2 spillover mechanism. This strategy allows the facile synthesis of ND-induced CNT growth and achieves high H2 sensing performance via a scalable method.