Silver nitrate doped chitosan acetate films and electrochemical cell performance

Chitosan acetate-silver nitrate (AgNO3) complexes were prepared in thin film form by the solution cast technique. The electrical conductivity sigma of the films was measured by impedance spectroscopy. The plot of sigma vs. dopant content indicates that sigma increases with increasing dopant content up to a dopant amount of 0.25 g where sigma reaches a maximum. The plot of ln sigma T vs. 10(3)/T (278 K less than or equal to T less than or equal to 313 K) for each film sample seems to obey the Arrhenius rule. Here sigma is the electrical conductivity and T is temperature in Kelvin. From these plots the activation energy, E-A was obtained and the graph of activation energy versus dopant content was plotted. From these plots the increase in sigma can be explained in terms of the decrease in E-A. The shape of the Cole-Cole plots seem to imply that the transport mechanism of Ag+ ions occurs by way of diffusion. The film with the highest ionic conductivity of 2.6 x 10(-5) S cm(-1) was used to fabricate Ag/AgNO3 -- chitosan/I-2 electrochemical cells. The average open circuit voltage of these cells is 0.672 V justifying the material to be an Ag+ ion conductor. By the electromotive force method, the ionic transference number of the film is 0.98 implying the low electronic conductivity of the material and its suitability as an electrolyte for electrochemical cell fabrication. Characteristics of such cells are presented and discussed. (C) 1997 Elsevier Science S.A.