Dynamic Electrochemistry of Polyaniline Nanoparticle Dispersions

Solid electroactive nanoparticles could be electrochemically oxidized/reduced at solid electrodes, transferring large amounts of charge. Therefore, concentrated dispersions of particles could be used in flow batteries. [1] While an extensive experimental and theoretical work has been made on the electrochemistry of single small nanoparticles (nanoimpact regime)[2], the dynamic electrochemical behavior of large ensembles of electroactive nanoparticles has not been studied. In the present work we describe the experimental study of different dispersions of polyaniline nanoparticles. Polyaniline is a well-known material for conventional batteries.[3] It is shown that nanoparticle adsorption occurs in glassy carbon electrodes. Besides, the charging/discharging of the nanoparticle dispersion is controlled by the combined effect of the nanoparticle diffusion in the electrolyte (which controls the residence time in contact with the electrode) and the charge diffusion inside the nanoparticle (which control the single particle charging/discharging). While small nanoparticles can be changed in a short time, the residence time is also limited due to the larger diffusion coefficient. Therefore, a maximum efficiency of conversion is observed. Moreover, the conversion efficiency could be increased by increasing the viscosity of the electrolytes. On the other hand, the efficiency could be largely increased by introducing a redox mediator which shuttle the charge between the dispersed nanoparticles and the solid electrode. The relevance of the rate of charging/discharging towards the flow battery applications will be discussed. References Z. Qi and G.M. Koenig, J. Vac. Sci. Technol. B. 35, 40801:1-27, 2017. E. Katelhon, et al, J. Phys. Chem. C. 120, 17029-17034, 2016 and refs therein. C. Barbero, et al, J. Mater. Chem., 4, 1775-1783, 1994.