The electrochemical reactivity of amorphous hydrogenated carbon nitrides for varying nitrogen contents: The role of the substrate

A series of hydrogenated carbon nitride films have been deposited on titanium and n-type highly doped (1 0 0) silicon substrates by the integrated distributed electron cyclotron resonance reactor from acetylene and nitrogen gas mixtures. It has been found that for nitrogen content between 5 and 25% the electrical conductivity and the electrochemical reactivity, for an outer sphere reaction such as that due to the ferri-ferrocyanide system, varies in opposite directions. In addition the overall kinetic behaviour of the same system, looking similar to that of a simple electron transfer with a partial mass transfer in solution, contains another contribution. This can be explained by the presence of a more resistive layer within the carbon film and close to the solution, where electronic transport would occur by hopping between a large number of localised states. Finally, in contrast to the silicon substrate which introduces a resistive layer resulting in an additional potential drop, titanium seems to be a more promising substrate because of the negligibility of the latter effect.