Recycled polycrystalline CdS film electrodes with enhanced photo-electrochemical characteristics

Waste cadmium sulfide (CdS) film electrodes, originally deposited onto glass/fluorine doped tin oxide (glass/FTO) substrates, were used to prepare recycled CdS film electrodes. The waste glass/FTO/CdS were processed in acidic media to recover the glass/FTO substrates, the Cd2+ ions (in the acidic solutions) and the gaseous H2S (recaptured in basic media). All components of the waste electrodes were thus recovered. The recovered glass/FTO and the Cd2+ ions were then reused to produce new recycled glass/FTO/CdS electrodes by chemical bath deposition. The produced films were then characterized by X-ray diffractometry, scanning electron microscopy, electronic absorption spectroscopy and other techniques. The Cd2+ ions were recovered with efficiency higher than 90% from the waste films, as observed from atomic absorption spectrometry. The recycled films were assessed in photo-electrochemical conversion of light to electricity, and exhibited comparable efficiency to those freshly prepared from authentic starting materials and other literature values. Photoelectrochemical characteristics for the recovered films were further enhanced by avoiding stirring of the chemical deposition bath during preparation. The results manifest the feasibility of recycling CdS electrodes and enhancing their photo-electrochemical characteristics by simple low cost methods. Both environmental protection and economic goals can thus be potentially achieved.