Electrochemical Preparation Of ZnO,ZnFe₂O₄and α-Fe₂O₃Photoanodes And Their Photoelectrochemical Performance

In recent years, with the sustained and rapid economic development, the problems of energy and environment have been more and more serious. People are trying to find some new energy to replace the traditional energy and new methods to solve environment problems. As a clean, abundant and inexhaustible energy, solar energy will play a crucial role in the sustainable development of human society. In order to meet the demand for energy, the photovoltaic conversion of solar energy and the improvement of conversion efficiency will be important.ZnO, ZnFe2O4and a-Fe2O3semiconductor materials are synthesized by electrodeposition, and then their structure, morphology, and photoelectrochemical performances have been discussed. The content of this thesis are listed as following:(1) ZnO nanoplates film synthesized by pulsed electrodeposition and its photoelectrochemical performance. High-quality nanorods ZnO film has been grown by pulsed electrodeposition in10mM Zn(NO3)2, and then the nanorods ZnO are transformed into nanoplates by the incorporation of Ca2+in the solution. The changes of the morphology and crystal orientation confirm the possible mechanism:face-selective electrostatic. The results of EDS and PL both confirmed that no Ca2+existed in the crystal lattice of ZnO. The constrast of J-E curves indicated better photoelectric performance of nanoplates ZnO than nanorods ZnO photoanode.(2) ZnFe2O4thin film synthesized by electrodeposition and its photoelectrochemical performance. ZnFe2O4films are electrodeposited onto ITO substrates from the87mM Fe3+-30mM Zn2+-TEA-2M NaOH system, and then the films are annealed in Ar and O2atmosphere at500℃for3h, respectively. The samples after annealing are characterized by XRD、SEM、Raman、UV-Vis、XPS. The results both confirm the high degree crystallinity with cubic spinel structure and well-developed octahedral shape ZnFe2O4particles, however, compare the photoelectrochemical performance of the film annealed in Ar atmosphere with the films annealed in O2atmosphere and before annealing, we find that ZnFe2O4film annealed in Ar atmosphere show good potoelectrochemical property, while the others show no potoelectrochemical properties. As EDS analyses in composition shows a higher amount of element carbon which originate from the carbonizing process of TEA in Ar atmosphere than the others, accordingly, we conclude that element carbon existed in Ar annealed ZnFe2O4film helps the electron transference across the sample, and then completing the circuit.(3) α-Fe2O3thin film synthesized by electrodeposition and its photoelectrochemical performance. First, the black Fe3O4film is electrodeposited onto ITO substrate from the87mM Fe3+-100mM TEA-2M NaOH system, and then reddish-brown Fe2O3thin film was obtained by Fe3O4film heating in O2atmosphere at500℃for5h. The characterization results of the annealed film turn out the trigonal system and well-developed polyhedron shape of the α-Fe2O3, and the film also shows good potoelectrochemical property.