Measured versus Theoretical Redox Potentials

Figure 7 The open-circuit photovoltage plotted versus the difference between the work function of the substrate in vaccum, 8 , v.ac> and the solution redox potential, 4>redox- The work function of the substrate in the solution, 8 , the quantity of interest, is difficult to measure directly, but it is related to 8 , vac see the discussion in Ref. 12. The four types of substrates are, from left to right, ITO, Sn02, Au and Pt the filled diamonds are for 0.5 M Lil solution, the open circles are for 0.05 M ferrocene in 0.1 M LiCI04 solution, and the filled triangles are for 0.05 M hydroquinone in 0.1 M LiCI04 solution. The theoretical line shows the behavior predicted by the junction model. (Data from Ref. 12.)...

Figure 8.18. Measured redox potentials in a deep groundwater. Experimental values of the measured redox potentials (recalculated to the standard hydrogen electrode scale) versus (3pH + log[Fe ]). The concentration of [Fe J has been obtained from the analytical determinations by correction for the complex formation with carbonate. The notation refers to the different test sites. The full-drawn line has been calculated using the selected value of the standard potential E. The straight line has the theoretical Nemstian slope of +0.056 V, at the temperature of measurements. (Adapted from Grenthe et al., 1992.)...

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