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Dynamic E-ph Diagrams

IP.com Disclosure Number: IPCOM000062229D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

McBride, DG: AUTHOR [+2]

Abstract

When thermodynamic equilibrium conditions are present in aqueous solutions and the equilibrium constant of reaction is known, the stability of various species in the solution can be represented by a Pourbaix diagram, which shows the relationship between electrochemical potential and pH of the solution. When equilibrium conditions exist, Pourbaix diagrams can be used to spe the species present in solution over the ranges of potential and pH. However, Pourbaix diagrams cannot be used to accurately predict the species present in solution under conditions where thermodynamic equilibrium is usually absent due to the effects of chemical transport and reaction rate variations.

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Dynamic E-ph Diagrams

When thermodynamic equilibrium conditions are present in aqueous solutions and the equilibrium constant of reaction is known, the stability of various species in the solution can be represented by a Pourbaix diagram, which shows the relationship between electrochemical potential and pH of the solution. When equilibrium conditions exist, Pourbaix diagrams can be used to spe the species present in solution over the ranges of potential and pH. However, Pourbaix diagrams cannot be used to accurately predict the species present in solution under conditions where thermodynamic equilibrium is usually absent due to the effects of chemical transport and reaction rate variations.

In order to determine the species on a reaction surface when thermodynamic nonequilibrium conditions apply, a procedure for producing dynamic E-ph diagrams has been developed. Cyclic voltammagrams are conducted at various pH and agitation conditions in the desired solution by scanning potential and measu current. As the various species occur, a peak in potential is detected. The relationship between this potential and the pH level is plotted to define zones that indicate the presence of the various species.

Disclosed anonymously.

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