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

Abstract

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.