Pourbaix (E–pH-M) Diagrams in Three Dimensions

Abstract

E–pH (Pourbaix) diagrams provide an important graphical link between the thermodynamic calculations of potential, pH, equilibrium constant, concentration, and changes in Gibbs energy and the experimentally observed behavior of species in aqueous solutions. The utility of E–pH diagrams is extended with the introduction of an additional variable, X, which is a property of one of the pertinent species such as concentration. By allowing an investigator to visualize the interdependence of three variables, these three-dimensional E–pH–X plots increase interpretive capabilities. The full usefulness of such three-dimensional diagrams is realized when the image is freely rotatable. The reader is taken through the historical development, use, and construction of two-dimensional E–pH diagrams and is then introduced to the methodology for producing the three-dimensional diagrams in detail for magnesium, aluminum, and iron. Supporting information is supplied such that readers can access and use the freely rotatable diagrams.

Operando Characterization of Iron Phthalocyanine Deactivation during Oxygen Reduction Reaction Using Electrochemical Tip-Enhanced Raman Spectroscopy

“…The irreversible demetalation of FePc during ORR can be rationalized considering the large degree of molecular distortion and the thermodynamic driving force that favors solvated Fe 2+ formation, most likely a hexaaquairon­(II) complex. One consequence of FePc adopting a nonplanar geometry is an outward displacement of the Fe ion, which leads to an increase in the Fe–N bond length. ,,, Moreover, a solvated Fe 2+ is the thermodynamically stable Fe species under the ORR condition based on the Pourbaix diagram of Fe . Lastly, a smaller Pc cavity is necessary to accommodate the smaller Fe 3+/4+ ions that can form during ORR, which can induce further ring deformation .…”

Novel Reaction Media of Na2CO3–CaO for Silicon Extraction and Aluminum Removal from Diamond Wire Saw Silicon Powder by Roasting–Smelting Process

“…In order to prejudge which reactions could occur during the silicon recovery process with the addition of Na 2 CO 3 and CaO, it is necessary to investigate the standard Gibbs free energy values for the possible reactions. The Al containing phase in DWSSP can be regarded as Al 2 O 3 or Al 2 O 3 ·3H 2 O. ,− The possible reactions during the DWSSP smelting process in the presence of Na 2 CO 3 and CaO are shown in reactions –, − and the state of matter for each substance is selected as the most stable state. The Gibbs free energy values were calculated at different temperatures and 1 atm using software Factsage 7.2 , with the results shown in Figure . …”

Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities

“…Abbreviations: bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, ppy = 2-phenylpyridinato- A sample Pourbaix diagram of magnesium in water; the dashed blue lines represent the potentials at which water is oxidized (top line) and reduced (bottom line). Reprinted with permission from [43]. Copyright 2012 American Chemical Society.…”