Hydrogen Evolution in a Photoelectrochemical Cell with Ti-Doped Pyrite As Photoanode
Ti-FeS2 thin films have been grown by sulphuration of Fe layers (100 nm) thermally evaporated on discs in a vacuum sealed ampoule at 300 ºC. Film morphology and crystallinity were investigated by Scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Cubic FeS2 was identified as the unique phase at 300ºC (Fig1).
Electro- and photoelectrochemical measurements have been carried out using a conventional three-electrode glass cell with a quartz window (PEC) to illuminate the photoanode, i.e. the Ti-FeS2 samples used as working electrode. As counter electrode a platinum sheet was used and the reference one was a Ag/AgCl reference electrode. 0.5M Na2SO3 aqueous solution was used as electrolyte, which serves both, to increase the conductivity and as sacrificial agent. An halogen lamp (200 W) was utilized as white light source. Photocurrents show positive values, as expected from the doping with titanium, because as far as we know, pure pyrite thin films always present p-type conductivity3, but Ti doped pyrite show n-type behavior4,5.
A mass spectrometer connected to the PEC is used to measure the evolved H2 from the photoelectrochemical water splitting. Results show that Ti-FeS2 exhibit a high flow of photogenerated hydrogen from bias potential such low as 0.5V (vs. Ag/AgCl). In fact, strong bubbling hydrogen was experimentally observed in our photoelectrochemical cell and quantified with the mass spectrometer (Fig. 2).
In conclusion, the hydrogen photogeneration by using Ti-FeS2in a PEC under bias potential has been demonstrated. Quantitative results will be exposed in the oral communication.
Financial support from MINECO (MAT2011-22780) is acknowledged. Authors thank to F. Moreno for his technical assistance.
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