Facile fabrication of tin-doped hematite photoelectrodes - Effect of doping on magnetic properties and performance for light-induced water splitting

We present a new, easily scalable method for the deposition of nanocrystalline hematite photoelectrodes based on the spin-coating of a mixed solution containing tin(ii) and iron(iii) chlorides followed by thermal treatment. Our facile approach does not require any additional film-forming organic species and allows simple control of the photoelectrochemical performance of the electrode by adjusting the degree of tin doping. When annealed at 650 °C a strong increase in the water oxidation photocurrent is observed with increasing tin concentration. The maximum performance (0.45 mA cm ^-2 at 1.43 V vs. RHE) was found at the highest possible tin loading (20:100, Sn:Fe). The contrasting performance of electrodes annealed at 650 °C and 800 °C suggests different activation processes for dopant diffusion and activation. The doping of tin into the crystal structure of hematite thin films is directly evidenced by X-ray photoelectron spectroscopy and indirectly by changes in the intrinsic magnetic parameters (Morin temperature, Néel temperature) of the hematite films. The magnetization measurements thus represent a potential technique to quantify doping amounts in hematite.