Abstract
This study successfully synthesized aligned carbon nanotube/ manganese dioxide (CNT/MnO2) composite material by rapid heating and cooling chemical vapor deposition followed by electrochemical deposition. Different lengths of CNT/MnO2 composites can be easily obtained by controlling CNT growth durations. The longer CNTs with a length of 250 μm show higher specific capacitance because they possessed higher conductivity as compared with shorter CNTs with a length of 20 μm. The content of MnO2 in the composite, simply controlled by electrochemical deposition time, affected the morphology, microstructure and the capacitive behavior of CNT/MnO2. It is found that the specific capacitance increased with MnO2 amount and decreased when longer MnO2 deposition time was used. Compared with the longer CNT/MnO2, the shorter one exhibits better capacitive behavior; the specific capacitance of short-CNT/MnO2 (240 s) reached 148 F/g which is much higher than 69 F/g of long-CNT/MnO2 (160 s). In order to increase the contact area between CNT and the electrolyte, this study prepared patterned Si substrate using photolithography and reactive ion etching and synthesized patterned-CNT/MnO2. Higher specific capacitance of patterned-CNT/MnO2 was obtained indicating that increasing the contact area could effectively improve the capacitive performance of the electrode; in addition, the patterned-CNT/MnO2 (80 s) demonstrates a high specific capacitance of 168 F/g.