title: Electrolyte diodes with weak acids and bases. I. Theory and an approximate analytical solution.
abstract: Until now acid-base diodes and transistors applied strong mineral acids and bases exclusively. In this work properties of electrolyte diodes with weak electrolytes are studied and compared with those of diodes with strong ones to show the advantages of weak acids and bases in these applications. The theoretical model is a one dimensional piece of gel containing fixed ionizable groups and connecting reservoirs of an acid and a base. The electric current flowing through the gel is measured as a function of the applied voltage. The steady-state current-voltage characteristic (CVC) of such a gel looks like that of a diode under these conditions. Results of our theoretical, numerical, and experimental investigations are reported in two parts. In this first, theoretical part governing equations necessary to calculate the steady-state CVC of a reverse-biased electrolyte diode are presented together with an approximate analytical solution of this reaction-diffusion-ionic migration problem. The applied approximations are quasielectroneutrality and quasiequilibrium. It is shown that the gel can be divided into an alkaline and an acidic zone separated by a middle weakly acidic region. As a further approximation it is assumed that the ionization of the fixed acidic groups is complete in the alkaline zone and that it is completely suppressed in the acidic one. The general solution given here describes the CVC and the potential and ionic concentration profiles of diodes applying either strong or weak electrolytes. It is proven that previous formulas valid for a strong acid-strong base diode can be regarded as a special case of the more general formulas presented here.
authors.affiliation: Center for Complex and Nonlinear Systems and the Department of Chemical Physics, Budapest University of Technology and Economics, Budapest H-1521, Hungary.
authors.forename: Kristóf
authors.initials: K
authors.lastname: Iván
authors.forename: Péter L
authors.initials: PL
authors.lastname: Simon
authors.forename: Mária
authors.initials: M
authors.lastname: Wittmann
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Noszticzius
mesh_terms: D000143:Acids; D002623:Chemistry Techniques, Analytical / Q000379:methods; D002627:Chemistry, Physical / Q000379:methods*; D004058:Diffusion; D004573:Electrolytes; D004581:Electronics; D004867:Equipment Design; D007477:Ions; D008956:Models, Chemical; D015233:Models, Statistical; D008962:Models, Theoretical; D008968:Molecular Conformation; D016012:Poisson Distribution; D013816:Thermodynamics
chemical_list: D000143:Acids; D004573:Electrolytes; D007477:Ions