Voltammetry of azobenzene microcrystals

Azobenzene solid particles have been mechanically attached to a graphite electrode and measured by cyclic staircase voltammetry. Well-developed and widely separated cathodic and anodic peaks were observed. Redox reaction is controlled by both the heterogeneous charge transfer kinetics and the mass transfer. Its mechanism is explained by the surface diffusion model. Reaction starts at the three-phase boundary, where electrons are transferred from the electrode surface to the attached azobenzene molecules. The electrons are then propagated over the surface of microcrystals by a series of exchange reactions between hydrazobenzene and azobenzene molecules, with the participation of proton donors from the solution. The apparent mass transfer occurs in this way. In the crystal lattice the transmission of protons is not possible, and consequently there is no propagation of electrons.