Fabrication and characterization of composite TiO2 nanotubes/boron-doped diamond electrodes towards enhanced supercapacitors

The composite TiO2 nanotubes/boron-doped diamond electrodes were deposited using Microwave Plasma Enhanced Chemical Vapor Deposition resulting in the improved electrochemical performance. This composite electrode can deliver high specific capacitance of 7.46 mF cm(-2) comparing to boron-doped diamond (BDD) deposited onto flat Ti plate (0.11 mF cm(-2)). The morphology and composition of composite electrode were characterized by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. According to XPS and Raman analyses, the structure of TiO2 was greatly changed during Chemical Vapor Deposition process: formation of Ti3+ sites, partial anatase to rutile transformation and titanium carbide phase formation. This effect is attributed to the simultaneous presence of activated hydrogen and carbon in the plasma leading to enhanced dehydration of NTs (nanotubes) followed by carbon bonding. The enhanced capacitive effect of TiO2 NT/BDD could be recognized as: (1) the unique synergistic morphology of NTs and BDD providing more efficient conducting pathway for the diffusion of ions and (2) partial decomposition of NTs and transformation towards to TiC and Ti2O3 fractions. Finally, highly ordered titania nanotubes produced via simply, quick and controllable method - anodization, could act as promising substrate for conductive BDD layer deposition and further application of such composites for supercapacitor construction. (C) 2015 Elsevier B.V. All rights reserved.