Fabrication of a hydrogen gas sensor composed of carbon nanotubes and catalytic palladium using dielectrophoresis

摘要

The authors have proposed a novel fabrication method of carbon nanotube (CNT) gas sensor using dielectrophoresis (DEP). One advantage of the DEP fabrication technique is that one can build up interface between the electrode and CNT or CNT and the other nano materials. In this paper, three different types of sensor, Cr electrode/CNT sensor, Pd electrode/CNT sensor and Pd nano particle/CNT sensor were fabricated by using the DEP method aiming to develop a CNT-based hydrogen gas sensor. At the moment of H{sub}2 (diluted with air) exposure, the conductance of Pd electrode/CNT sensor and Pd nano particle/CNT sensor decreased at first, and then turned to increase in the later stage. The conductance decrease just after the H{sub}2 exposure was probably due to reducing CNTs by H atoms, which were produced by dissociative adsorption of H{sub}2 molecules on catalytic Pd surface. In the later stage, the dissociated H atom might react with dissociated oxygen atom to create H{sub}2O accompanying heat generation. The exothermic reaction might increase temperature and the conductance of the semiconducting CNT. On the other hand, the Cr electrode/CNT sensor did not respond to H{sub}2.