| Hydrogen is envisioned as a viable fuel of the future. Photoelectrochemical (PEC) hydrogen generation by water splitting reaction is the most promising method to obtain renewable hydrogen. The U.S. Department of Energy has determined that for PEC hydrogen to be economically feasible, and competitive with steam reforming hydrogen production, a solar-to-hydrogen efficiency of 10% maintained for 1,000 hours of operation is required. Selection of durable photo-electrodes capable of withstanding the harsh aqueous environment in PEC hydrogen generation is an important factor. Semiconductor nanostructured metal oxides, such as titanium dioxide, are generally more stable in such environments, making them suitable candidate materials.;In the present investigation, self-organizing nanotubular titanium dioxide synthesized by electrochemical anodization and heterostructures thereof were examined for PEC hydrogen generation. In the first part, new synthesis methods were explored such as light-assisted anodization, surface treatment prior to anodization to achieve hierarchical nanotubular titanium dioxide, and binary acid anodization for in situ metal doping. A mechanism for pore nucleation and nanotube wall separation has also been proposed. In the second part, titania nanotubes were sensitized with nanocrystalline CdO, CdS, and Mn2+ or Co2+ doped CdS as visible light absorber layers. The material properties were examined using different characterization techniques such as scanning electron microscopy (SEM), x-ray diffraction (XRD), ultra violet-visible (UV-vis) photospectroscopy, x-ray photon spectroscopy (XPS), and Raman spectroscopy. The PEC activity of the photoanodes was examined under simulated air mass (AM) 1.5 irradiation. Electrochemical impedance spectroscopy and Mott-Schotty analysis were also used to ascertain the PEC results and correlate with material properties. |
