Reorganization Energy of a Solvent

Using the results presented above, one can suggest a method of determining the reorganization energy from data on photoemission of electrons from solutions into the vapor phase (see review ). 

The quantity Wph can be found from the dependence of the photoemission current on the light quantum energy by extrapolating it to the zero current. Reference 27 reports the work function as 5.95 eV for photoemission from aqueous solutions of FeCCN) . Using the standard potential of the system Fe(CN)6 /Fe(CN)6 as +0.36 V (relative to the normal hydrogen electrode), we obtain for the reorganization energy of water around ferrocyanide/fer-ricyanide ions 5.95 - 4.4 - 0.36 — 1.2 eV. For the system considered, the electron transfer reaction is an outer-sphere one, so one can take = R,red = Er. 

It is of interest that Reference 28 reports for the system Fe(CN)6 /Fe(CN)6 the homogeneous value 1.24 eV obtained by model calculation, which agrees well with the value presented above. As for the heterogeneous reorganization energy, the same paper reports, as it might be expected, a much lower value (0.4 eV) obtained from tunnel currents measured on heavily doped Sn02 electrodes. 

SPECIFIC FEATURES OF THE STRUCTURE OF THE SEMICONDUCTOR/ELECTROLYTE INTERFACE 

An electrical double layer arises at the semiconductor elec-trode/electrolyte solution interface, as in the case of the metal/sol-ution interface. The double layer consists of the plates carrying charges of opposite sign, each plate being located in one of the phases in contact. In the near-surface region of the semiconductor the charge is formed as a result of redistribution of electrons and holes, while in the solution it is formed as a result of ion redistribution. Under equilibrium conditions, the absolute values of these charges are the same. 

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