Photoelectrochemical cells using polycrystalline and thin film MoS₂ electrodes

Using well-crystallized starting materials, polycrystalline electrodes of MoS₂ are found to give significant photoresponse in aqueous polyiodide. Best results are obtained with multicrystalline lumps affixed to metal substrates; pressed pellets reach about 30% of the output of these former ones. Thin polycrystalline films, prepared by flux annealing of pasted films show some photoresponse, which can be improved by more than an order of mangitude if an organic polymer binder is used in the preparation and retained by low temperature annealing. Such electrodes reach 50% of the output of pressed pellets. The action of the organic polymer seems to be twofold: orientation of crystallites, and some passivation of exposed edges on the electrode surface. While prolonged use of these photoelectrodes, as well as short use at higher temperatures, decreases their output, the original activity can be nearly restored by renewed low temperature annealing. The wavelength dependence of the photoresponse of these electrodes shows that those using a polymer matrix approach that of single crystals most closely.