Simple Solvothermal Approach to Highly Nanostructured Hematite Thin Films

In this work, we present a solvothermal method for the synthesis of hematite thin films on fluorine-doped tin oxide
substrates. This simple method uses a precursor solution of iron(III) 2,4-pentanedionate dissolved in ethanol with a
microliter-scale amount of water and yields hematite ~ 500-nm thick films after annealing. The synthesised films
were characterised using an array of methods, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, diffuse reflectance, and powder x-ray diffraction. Incorporating water into the precursor solution provides nucleation sites for the reaction and results show that by altering the amount of water used in the synthesis, it is possible to generate nanocrystalline films of different morphologies, nanocrystal size distributions, and surface areas. This synthetic procedure therefore provides control over the films’ physical and electrochemical characteristics. Doping of hematite thin films is also possible using this synthesis, as exemplified by doping with tin by adding tin(II) 2,4-pentanedionate to the precursor solution. To demonstrate utility, we build prototype photoelectrochemical cells using the synthesized hemtatite as the photoanode.