Electrochemical Processes of InP in HNO 3 and HCl in the Dark

Abstract

Electrochemical polarization studies were performed on in and solutions without illumination to determine the effect of potential and pH (in the range 0–6) on the anodic and cathodic reactions. Products on the surface were identified by x‐ray diffraction and x‐ray photoelectron spectroscopy. In the dark, the electrochemical behavior of was shown to be independent of pH and electrolyte concentration. The dissolution of in and is strongly inhibited, even at the lowest pH values, by the formation of a coherent film of . The formation of this phase is predicted from thermodynamic data. The reduction of holes in the valence band is suggested as the main reduction process under open‐circuit conditions. Evolution of hydrogen gas does not take place until the second Tafel region on the cathodic branch appears. The anodic polarization of shows two characteristic passive regions, the first of which is likely due to the completion of the lateral growth of oxide islands along the surface; this film is protective and leads to an effective suppression of the charge transfer. As the potential increases to more positive values, a second passive region is reached. Here, the existence of a multiphase oxide layer was revealed by x‐ray diffraction.