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Nano-scale Electrode of Magnet-photo Fuel Cell

出版	University of Toledo, 2013
URL	http://books.google.com.hk/books?id=XO-xAQAACAAJ&hl=&source=gbs_api

註釋Nowadays, it is necessary to find a new energy conversion method to solve the energy crisis. Environmental pollution is another critical problem which needs to be solved. In addition, solar energy is a clean, abundant, reproducible energy source in the world. Photoelectrochemical fuel cell (PEC) is an energy conversion and pollutant-clean system using solar energy. The significant characteristics of PEC are the generation of electric energy, the splitting of the water, and degraded contaminative solutions. Nowadays, the PEC field is still short of intensive research because this is an interdiscipline which includes physics, chemistry, electrology, and mechanics. The efficiency of the PEC is still too low in terms of the practical application in industry. With the nano technology's development, researchers found that nano-structured photovoltaic materials can enhance the performance of PEC. There are multiple choices of materials which can be SiO, GaAs, GaAlAs, InP, CdS, CdTe, etc. Researchers are focusing on choices and fabrications of materials. In my study, I concentrate on TiO2 nano-structured materials-based photo anode of PEC. Firstly, I studied the mechanical and photoelectrochemical response of titanium dioxide nanotube on pure titanium. Self-organized high aspect ratio TiO2 nanotubular array structures were prepared through electrochemical oxidation of pure titanium or titanium alloys. To test the mechanical response of the nanotube, damping characteristics of three types of specimens were investigated using the logarithmic decrement method. The damping ratios and fundamental natural frequencies of TiO2 nanotube were obtained. The mechanical properties of TiO2 nanotube is important because it is relative with the stability of anode and piezoelectric behavior in the PEC. Secondly, I investigated the temperature effect on PEC. The temperature is an important factor on PEC, and there is no study on this aspect yet. The temperatures' range is very broad, and is selected from 20°C to 100°C. Finding the appropriate operation temperature is important for the maximization of the power of PEC. I used glycerol and urea as fuels. The concentrations are 10%, 20%, 30% of glycerol, and 0.25 M, 0.5 M, 1 M of urea, respectively. Open circuit voltages were tested at different temperatures, fuels and concentrates in order to verify temperature effect. I found the higher temperature will decrease the performance of PEC; for example, the photo voltage of PEC is 0.18V at 24°C, but the photo voltage of PEC only is 0.05V at 73°C in 1M urea. Time-dependent behavior also was modeled. Thirdly, in order to improve the photo catalysis of the PEC, I studied Fe2O3, CuO, NiO, Ag@CuO, Ag@NiO, and Fe2O3@CuO@NiO doped TiO2 nanotubes as the photo anodes. Polyaniline (PANi) is a conducting polymer with conjugated structures, also doped into TiO2 nanotube. TEM and EDX spectrum analysis was performed to reveal the structure and composition of the anodes. In order to measure the current response, linear sweep scan in the voltage range from 0-2 V and at the constant bias voltages of 0.5, 1.0, 1.5, 2.0 V were applied to the PEC. The applied bias effect in PEC system of urea solution is noticeable. Visible light (Vis), ultraviolet (UV) light and UV+Vis light were used in the test. Current densities and photo current densities of the PEC with different doped photo anodes were tested on a CHI 400A workstation. I found that NiO doped nanotube had maximum photo current density which was 54.5 mA/m2 under Vis light compared with others. Fe2O3 doped nanotube had maximum photo current density which was 178.54 mA/m2, and 201.85 mA/m2 under UV light, and UV+Vis light compared with others. Fourthly, I investigated the photoelectrochemical responses of TiO2 nanotube anode in ethylene glycol (EG), glycerol, ammonia, ethanol, urea, and Na2S electrolytes with different concentrations. Compared with other researches, the type of solutions and concentrations' range was comprehensive. Finding the appropriate fuel concentration is significant because the power of PEC is effected by it. The range I selected is from 0 to saturated, but no one did this before. The TiO2 nanotube anode was highly efficient in photoelectrocatalysis in these solutions under UV light illumination. The photocurrent density is obviously affected by the concentration change. Na2S generated the highest photocurrent density which is 450 mA/m2, but its concentration does not significantly affect the photocurrent density. Urea shows high photo voltage, which is 0.3V at proper concentration and low photocurrent at different concentrations. Externally applied bias voltage is also an important factor that changes the photoelectrochemical reaction process. In view of the open circuit voltage, EG, ammonia and ethanol fuel cells show the trend that the open circuit voltage (OCV) increases with the increase of the concentration of the solutions. Glycerol has the highest OCV compared with others and it decreases with the increasing of the concentration because of the high viscosity. The OCV of the urea and Na2S solutions didn't show an obvious concentration effect. Finally, I designed and developed a magnet-PEC based on the Hall Effect. The magnetic field enhanced the photoelectrochemical response of a nanostructured titanium dioxide anode PEC. I developed a concept of permanent-magnet photo electrochemical fuel cell. The fuel cell container was made out of stainless steel. The responses of the anode to visible and ultraviolet lights were measured, along with the permanent magnetic field effect on the fuel cell. The increasing of open circuit voltage was 0.0564, 0.1625, 0.1898 and 0.376 V, under Vis, UV, magnet and magnet+UV excitation, respectively. Current density was measured under bias potential linear scan. The maximum magnet current density was 5.23 mA/m2 at 2 V bias and the maximum photo current density was 296.05 mA/m2 at 2V bias. The magnet response is even higher than UV and Vis light responses on open circuit voltage. The maximum value of photo voltage is 0.25 using pure water under a magnetic field. Magnetic field enhances the PEC is my unique finding.