PHOTOCORROSION OF POLYCRYSTALLINE CDSE IN AQUEOUS KOH - AN IN-SITU STUDY BY PHOTOCALORIMETRY

Photocalorimetry in conjunction with thermodynamical analysis has been employed to characterize the photocorrosion reaction of a semiconduct or electrode. The potential dependence of the heat-monitoring signal a nd of the photocurrent has been measured at a CdSe electrode (polycrys talline film on Ti) in 0.1 mol l(-1) aqueous KOH under 600 nm illumina tion. From these measurements a characteristic potential (E = -0.21 /- 0.02 V versus SHE) is obtained which connects the reversible potent ial and the Peltier coefficient of the corrosion reaction. These quant ities are specific for a given reaction. Values of E have been calcul ated for thermodynamically possible corrosion reactions of CdSe from t he respective standard potential, standard entropy change and heat of transport. Good agreement between the measured and calculated values o f E and the photocalorimetric detection of a light-absorbing corrosio n film indicate that CdSe + 20H(-) --> Cd(OH)(2) + Se + 2e(-) is the p redominating corrosion reaction under the present conditions. (C) 1998 Elsevier Science S.A. All rights reserved.