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A theory relating the electrochemical and solid‐state properties of semiconductors to their photoelectrochemical behavior has been used to predict the electrodes that, when combined, will give the optimum efficiencies for the splitting of water by means of solar light to hydrogen and oxygen. The present paper represents the first application of this theory. A p‐type indium phosphide electrode has been decorated with platinum and combined with an n‐type gallium arsenide electrode which has been protected against photocorrosion by depositing a thin film of Mn‐oxide on it. Examination has been made of the individual photoelectrochemical behavior of these electrodes in aqueous solution. The I‐V curves of these electrodes indicated that, when placed together in a cell, they would spontaneously give rise to hydrogen and oxygen when photoirradiated. X‐ray photoelectron spectroscopic examination of the protected gallium arsenide electrode showed no indication of the substrate, i.e., the Mn‐oxide completely covered the gallium arsenide. Ellipsometric examination showed the thickness of manganese oxide to be ∼200Å. When these two electrodes were used in a photoelectrochemical cell and irradiated at an intensity of ∼1 sun, photoelectrolysis of water took place. Evaluations of the solar conversion efficiency for the production of hydrogen and electricity showed a maximum total conversion efficiency of 8.2%, the conversion being predominantly to hydrogen. The efficiency as a function of time undergoes a decrease of about 10% during the first hour of operation, but then remains constant for at least a further ten hours.

Cadmium selenide and lead selenide films have been deposited by a solution growth technique on single crystal germanium and silicon, glass, mica, and copper substrates. The effect of bath parameters (pH, temperature, and relative concentration of reactants) and the nature of the substrate on the rate of deposition and terminal thickness has been established. The structure of the films has also been studied. Based on the experimental results, a growth model has been proposed.

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Fourier transform ellipsometry (FTE) and XPS techniques are used to characterize spectroscopically the passive film on iron with respect to the relation of the Fe2+/Fe3+ ratio to the water content. The conversion of the passive film from the lower to the higher valency state occurs between -0.3 and -0.2 V/NHE without significant change in its thickness. The presence of oxygen reduces conversion of the film, resulting in the reduction of the thickness of the film. The hydration of the passive layer depends on the degree of the conversion which precedes it and attains 80% at 0.0 V/NHE. The absorption spectra of Fe2+ (2.05 eV) and Fe3+ (2.3 eV) species in the film are due to Fe d-d transitions.Spectroscopic studies have contributed to a better understanding of the nature of the thin passive layer formed on iron. Thus, recently, new evidence for bound water1,2