Nanostructured (α-Fe2O3 Thin Films for Photoelectrochemical Hydrogen Generation

(alpha-Fe2O3 thin film photoelectrodes were fabricated by aerosol-assisted chemical vapor deposition (AACVD) using a new hexanuclear iron precursor [Fe-6(PhCOO)(10)(acae)(2)(O)(2)(OH)(2)].3C(7)H(8) (1) (where PhCOO = benzoate and acac = 2,4-pentariedionate). The precursor (1) designed for AACVD has a low decomposition temperature and sufficient solubility in organic solvents and was synthesized by simple chemical techniques in high yield. It was characterized by inching point, FT-1R, X-ray crystallography, and thermogravimetry (TGA), The TGA analysis proved that complex (1) undergoes facile thermal decomposition at 475 degrees C to give Iron oxide residue. In-house designed AACVD equipment was used to deposit highly crystalline thin films Of(alpha-Fe2O3 on fluorine-doped SnO2 coated glass Substrates at 475 degrees C in a single step. The material properties were characterized by XRD, XPS, and Raman spectroscopy, and the results confirmed that films were highly crystalline alpha-Fe2O3 and free from other phases of iron oxide. Further anlysis of XRD data of the thin films proved the formation of crystalline hematite with an average diameter of 35 nm. X-ray photoelectron spectroscopy (XPS) confirmed that Fe is present only ill (lie Fe 3 4 oxidation state. Scanning electron microscopy (SEM) showed that the needle-like particles having length in the range of 100 to 160 nm with a diameter of 30-50 rim are sintered together to form a compact structure Of the 80-nm-thick alpha-Fe2O3 A layer. Optical, electrical, and photoelectrochemical studies were conducted by UV-vis, electrochemical impedance spectroscopy, and steady-state current-voltage plots. The optical bandgap was estimated, and it is about 2.13 eV. The dollor density of the alpha-Fe2O3 was 2.914 X 10(23) m(-3), and the flatband potential is approximately -0.86 V vs V-Ag/AgCl. The Photoelectrochemical characteristics recorded under ANI 1.5 illumination indicated that the photocurrent density of 600 mu A cm(-2) at, 1.23 V vs RHE, which is among the highest reported for all undoped alpha-Fe2O3 photoelectrode to date.