VARIATIONAL PRINCIPLE FOR ENTROPY IN ELECTROCHEMICAL TRANSPORT PHENOMENA

Transport of energy, matter and electric charge is analyzed in the fra mework of a quasilinear variational formalism. A new extremum principl e extending that of Onsager to a nonstationary quasilinear regime is a pplied to electrochemical transport. The principle is set in physical space-time rather than in three-dimensional space and, as such, it sub stantiates the role of the entropy rather than the entropy production. For the prescribed state and/or fluxes at the system boundary the pri nciple implies a least possible growth of entropy under the constraint s imposed by conservation laws, which proves that the entropy plays a role in thermodynamics similar to that of action in mechanics. One can use the principle to derive nontruncated sets of the phenomenological equations, equations of change and bulk overvoltage properties in com plex systems. The paper prepares a background to dynamical formulation s for electrochemical processes. The nonequilibrium temperatures and c hemical potentials are interpreted in terms of the Lagrangian multipli ers of the variational principle for the entropy. These quantities con verge to the classical thermodynamic intensities when the local equili brium is attained in the system. (C) 1996 Elsevier Science Ltd