The Construction Of One - Dimensional Nanometer Materials And Its Application In Energy Conversion

Nowadays, the world is facing serious energy and environmental problems, so it is very urgent to produce a clean and sustainable energy using renewable energy source to solve such problems. The burning of fossil fuels is detrimental both to non-renewable resources and environment. Solar energy as a kind of inexhaustible energy can provide enough power for the human society. But low utilization efficiency and high cost limit the wide application of solar energy, thus, producing clean energy from solar energy based on semiconductors is an effective way to solve energy issue and environmental degradation. Among all the alternative energy, hydrogen energy has been regarded as the most promising alternative energy resource in 21 st century by the majority of scholars around the world.Semiconductor-based photochemical technology can utilized to transfer solar energy to chemical or electrical energy. TiO₂, as a classic semiconductor material with non-toxic, low price and photochemical stability, has been widely used to produce hydrogen. Nevertheless, the intrinsic defects of TiO₂, such as narrow absorption spectra, low utilization efficiency of solar light, high recombination rate of photo-induced electrons and holes, severely limited their practical application for energy and environmental remediation. Various strategies have been explored to solve these problems via full-band absorption TiO₂, noble metal modification and combination of photocatalytic and electro-chemistry for achieving photoelectrocatalysis. Thus, the present thesis focused on the following parts:（1） TiO₂ nanorods arrays were synthesized via hydrothermal method. The research focus on the performance of storage and transfer solar energy to hydrogen through water splitting. The results indicated that TiO₂ nanorods arrays film can realize the transfer of solar energy to electricity for storage, and such storage electricity can be further utilized to drive the water splitting. The main principle for the above energy transfer-storage relies the reversible conversion of Ti⁴⁺/Ti³⁺ through the electronic reduction ability for storage photogenerated electrons. And then, by convert Ti³⁺ to Ti⁴⁺ the electron can be released to reduce H2 on the platinum electrode. The as-prepared electrodes were characterized by X-ray photoelectron spectroscopy（XPS）, electrochemical methods and so on. The water splitting reaction provides a feasible way for solar energy storage with good photochemical stability.（2） Free-standing rutile TiO₂ single-crystal films with ordered nanostructures were prepared by solvothermal treatment. Based on the first part research, the TiO₂ film can be stripped from FTO glass through prolonging the time of hydrothermal process. Meanwhile, the conductive layer on FTO glass can be peeled off to form a conductive and free-standing film with orderly 1-D nanorod array structure. The as-prepared samples were characterized by X-ray powder diffraction（XRD）, field emission scanning electron microscopy（FESEM）, transmission electron microscopy（TEM）, Xray photoelectron spectroscopy（XPS） and photocurrent response. These results show that the conductive film can transfer electron faster owing to the heat stability and excellent performance in water splitting for hydrogen evolution.（3） MOFs（ZIF-8） modified TiO₂ photoelectrode was prepared by hydrothermal treatment. The sample of MOFs modified TiO₂ photoelectrode improve the absorption of CO₂, attributed to the open-framework structure of MOFs with excellent specific surface area. The modified photoelectrode exhibited a higher activity than pure sample for reducing carbon dioxide to organic fuels through photo-reduction.（4） A ternary composite in nanocones was synthesized by loading CdS nanorods on the reduced graphene oxide（RGO） grafted with C₆₀ clusters was prepared by solvothermal treatment for improving both the photo-stability and catalytic activity. Carbon materials(such as C₆₀ and graphene) has good capability for electron collection, effectively inhibiting the combination of photo-induced carriers. The introduction of unique hybrid structure facilitated the collection and transfer of photo-generated charges on CdS semi-conductor through the 2D planar surface of RGO to the vertex of C₆₀, leading to the diminished photoelectron-hole recombination and enrichment of photoelectrons onto C₆₀ active sites. As a result, the C₆₀-RGO/CdS hybrid displayed high H2 evolution efficiency. More importantly, this C₆₀-RGO/CdS photo-catalyst displayed excellent durability since the strong interaction of CdS with C₆₀-RGO and rapid consumption of photo-generated charges on CdS could efficiently enhance the stability of CdS against either the leaching or the photocorrosion. Adjusting p H value and introducing C₆₀ molecule, the position of valence band and conduction band be charged, which contribution to overall water splitting to produce hydrogen and oxygen based on CdS.