Ultrathin Carbon Film Electrodes from Vacuum-Carbonised Cellulose Nanofibril Composite

A novel way to produce ultrathin transparent carbon layers on tin-doped indium oxide (ITO) substrates is developed. The ITO surface is coated with cellulose nanofibrils (from sisal) via layer-by-layer electrostatic binding with poly(diallyldimethylammonium chloride) or PDDAC acting as the binder. The cellulose nanofibril-PDDAC composite film is then vacuum-carbonised at 500 degrees C. The resulting carbon films are characterised by atomic force microscopy (AFM), small angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and Raman methods. Smooth carbon films with good adhesion to the ITO substrate are formed. The electrochemical characterisation of the carbon films is based on the oxidation of hydroquinone and the reduction of benzoquinone in aqueous phosphate buffer media. A modest effect of the cellulose nanpfibril-PDDAC film on the rate of electron transfer is observed. The effect of the film on the rate of electron transfer after carbonisation is more dramatic. For a 40-layer cellulose nanpfibril-PDDAC film after carbonisation a two-order of magnitude change in the rate of electron transfer occurs presumably due to a better interaction of the hydroquinone/benzoquinone system with the electrode surface.