Decomposition Potentials of Crystalline Silicon as Related to the Photocurrent Stability of p‐n Junction Silicon Semiconductor Electrodes

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Abstract
The use of highly doped n+‐ or p+‐type silicon layers as electrodes allowed us to measure the onset potentials, , of anodic currents corresponding to the oxidation of Si in aqueous solutions of various pH's. The value obtained is 0.8–1.1V more positive than the thermodynamic redox potential for the Si oxidation, indicating that this electrode reaction has a large activation energy. No definite current peak corresponding to the formation or the re‐oxidation of surface silicon hydride was observed when scanned up to a potential ca. 1V more negative than the thermodynamic redox potential for the Si reduction, or scanned backward, showing that the Si reduction also has a large activation energy. From these results it is concluded that Si electrodes must be stable when used for the reaction of redox systems having the standard redox potentials close to or somewhat more negative than . Since is located at nearly the same level as the thermodynamic hydrogen evolution potential , this leads us to understand that Si electrodes are stable for use in hydrogen evolution either in the dark or by illumination. The values and the flatband potentials for n‐Si were nearly parallel to each other, and showed nonlinear dependence on pH.

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