Carbon nanotubes (CNTs) which are directly grown on nanoporous alumina templates by chemical vapor deposition are modified by radio frequency nitrogen -plasma at different times. Next, alumina is deposited onto the nanoporous alumina templates with grown CNTs by varying deposition times and pH values. Finally, aluminum oxide is annealed. Higher capacitance (2158.3 mu F/cm(2)) and higher operation voltage (57.10 V) are obtained at a better / superior nitrogen-plasma time (20 min) and better chemical liquid phase deposition conditions (time = 3 h and pH = 3.80). Furthermore, the longer the nitrogen-plasma time, the higher the capacitance. The longer the deposition time, the lower the capacitance, but the higher the operation voltage. The higher the deposition pH, the lower the capacitance, however, the higher the operation voltage. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.011206jes] All rights reserved.