Thermal sulfidation of α-Fe2O3 hematite to FeS2 pyrite thin electrodes: Correlation between surface morphology and photoelectrochemical functionality

The pyrite iron disulfide thin films are regarded as suitable candidates for construction of low-cost photoelectrochemical (PEC) solar cells. Iron oxide hematite has attracted much attention as possibly convenient material for hydrogen production via PEC water splitting. We refer on preparation of pyrite thin films via thermal sulfidation of hematite films synthetized by a physical methodology of high power impulse magnetron sputtering (HiPIMS) and purely chemical approach of sol-gel. We studied for the first time the correlation between PEC functionality of hematite films and after their sulfidation into pyrite. The highest PEC activity of hematite films of 560 μA cm−2 at 700 mV vs. Ag/AgCl was achieved with the HiPIMS photoelectrodes. The photoefficiency dropped dramatically to 4 μA cm−2 at 600 mV vs. Ag/AgCl after the sulfidation. A significant increase of grains‘ size, residual unreacted hematite, surface defects were the main reasons for the poor photoactivity. The sol-gel produced hematite yielded photocurrent of 30 μA cm−2 and a slight increase to 40 μA cm−2 (recorded at 500 mV vs. Ag/AgCl) of the corresponding pyrite version. Both these electrodes showed also similar morphological characteristics. The structural, electronic and optical properties of the deposited films were determined using various methods e.g. Raman spectroscopy, SEM, and PDS.