Synthesis Of Biomorphic Fiber Cerium Oxide And Its Artificial Photosynthesis

The evolution of nature has bred a variety of unique structure, configuration and properties, which provides a great impetus for the social civilization and the progress of history. Bionic technology is the imitation of human nature, so that artificial materials can possess the properties or structures of natural organism. Biological materials with hierarchical porous structure can be combined with inorganic functional materials through biomimetic synthesis, which can get the superior performance of non-polar porous materials. Part of the biological template synthetic materials with large specific surface area and high porosity, which can not only effectively increase reaction contact surface, but also keep biomass nitrogen source of the biological materials, thus photocatalytic performance has been greatly improved. From the initial petals, pollen, leaves to the subsequent virus, bacteria, proteins, biological templates have formed from the macro to micro, and finally extended to the whole nature. These special materials are shown to have excellent properties in the fields of artificial photosynthesis, automobile tail gas treatment, sensors manufacturing and biomedical science.Artificial photosynthesis which imitates the photosynthesis of green plants in nature, which can not only split water molecules to generate hydrogen for use as a clean fuel for vehicles, but also fix CO₂ to Reduce organic matter. Hydrogen is a kind of high energy fuel, which has the advantages of clean, pollution-free and resistant to storage and transportation. It can be converted into heat or electricity through burning. With the revolutionary potential as energy carrier, it can meet the scale of the world’s energy needs. However, the cost of hydrogen production is generally higher and the yield is lower. Facilitating the simple and inexpensive method of hydrogen production has become a common pursuit of a wide range of energy and environmental research workers. For the moment, the photocatalytic decomposition of water to hydrogen is mainly carried out in the UV range. In order to improve the solar energy utilization, it is necessary to develop a catalyst for photocatalytic decomposition of water in the visible region. On this view, ceria has received the greatest attentions as promising semiconductor photocatalyst. Bionic structure of CeO₂ has a higher catalytic performance both in the UV range and visible region. Therefore, hydrogen production by water splitting should also have high conversion efficiency. On this account, numerous solution-based efforts have been developed to design and fabricate particles CeO₂ photocatalyst with highly photocatalytic efficiency.Biomimetic nano CeO₂ materials were prepared by using loofah, cotton pads and bean sprouts as bio-templates through impregnation and thermal decomposition. For characterization of structure, fluorescence microscope, X-ray diffraction spectroscopy（XRD）, field emission scanning electron microscopy（FESEM）, transmission electron microscopy（TEM）, and nitrogen adsorption-desorption measurements were adopted. The results demonstrated that the samples not only completely removed the original bio-template, but also retained the morphology and microstructure of bean sprouts original templates. Then the biomorphic structure of fluorite structure CeO₂ material was obtained. Materials with cubic fluorite structure which can exactly copy the morphology of biological templates are composed of particles below 10 nm. The specific surface area of nano oxide cerium materials which are synthesized by template of loofah, cotton pads and bean sprouts are 148 m2/g, 118 m2/g and 168 m2/g, respectively.XPS and EDS were employed for detecting nitrogen-doped levels in hierarchical ceria,and possible chemical environments of the nitrogen in bionic ceria were discussed. The results show that it is successful biological nitrogen doping that the synthesized materials have retained the original biological nitrogen source of the templates. Nitrogen doping increases the oxygen defect ratio and the oxygen storage capacity of materials, thus the band gap material is reduced effectively, which enhances the absorption of visible light. The materials exhibit good photocatalytic activity in degradation of methylene blue and water photolysis experiments. The nano cerium oxide materials which are synthesized by template of bean sprouts on the degradation efficiency of methylene blue can almost reach 100% after 100 min, the product of hydrogen content can also reach 400μmol / g after 360 min.