| Nowadays,environmental pollution and energy shortage are two critical issues facing our planet.Among them,wastewater treatment is an important part for environmental protection.Every year,a huge amount of wastewater containing abundant chemical energy has been directly discharged into the natural environment,which not only does harm to ecological system,but also wastes energy resource.Hence,it is urgent to seek for new and efficient methods to remove pollutants and simultaneously recovery energy stored in wastewater.Photocatalytic fuel cell(PFC)is such a technology to address this issue.PFCs also offer several advantages of low cost,mild reaction conditions and short start-up time.Therefore,PFCs have received ever-increasing attention all over the world.In PFCs,there exists a complex process that involes the photon transport,mass transport,photo-excited electrons and holes transport,separation and recombination,photoelectrochemical reactions and so on.This process is inherently associated with the cell and photoanode designs,which affect the cell performance.However,conventional large-scale PFCs with the ion exchange membrane face the problems low mass transfer efficiency and long light path,which limit the improvement in the cell performance.Aiming at the above-mentioned issues,in this thesis,a membraneless and monolithic micro PFC(?PFC)has been designed.The membraneless and monolithic design can greatly increase the specific surface area,enhancing the photon and mass transport.Meanwhile,such design can make the cell system simple and easy to integrate with other microdevices.Besides,the use of laminar flow enables the separation of the photoanode from the cathode,eliminating the ion exchange membrane.Based on this design,a membraneless monolithic ?PFC with a UV light responsive TiO2 photoanode and oxygen-dissolved platinium cathode was firstly developed.Then,to address the oxygen transfer limitation caused by the oxygen-dissolved mode,a membraneless monolithic ?PFC with a UV light responsive TiO2 photoanode and air-breathing platinium cathode was developed.Furthermore,to address the problems of the low solar energy utilization efficiency,a membraneless monolithic ?PFC with a visible light responsive TiO2-photosenstized photoanode and air-breathing platinium cathode was developed.Finally,using CuO and TiO2-photosenstized as the cathode and photoanode materials,respectively,a membraneless monolithic ?PFC with dual visible light responsive photoelectrodes and air-breathing mode was developed,which not only decreased the capital cost but also further increased solar energy utilization efficiency.With these newly-devloped ?PFCs,the photo-response and durability were investigated.Effects of the operating parameters,including the methanol concentration,KOH concentration,light intensity and liquid flow rate on the cell performance were also studied.The main outcomes are as follows.(1)A membraneless and monolithic ?PFC with a UV light responsive photoanode and an oxygen-dissolved cathode was developed.The photo-response and its durability were studied.Results showed that the developed ?PFC was able to well respond to the illumination and a relatively good durability was attained.Parametric study indicated that the increases of the methanol concentration,KOH concentration and light intensity could improve the cell performance.There existed an optimum liquid flow rate leading to the maximum cell performance.(2)A membraneless and monolithic ?PFC with a UV light responsive photoanode and an air-breathing cathode was developed to enhance the oxygen transport at the cathode.The photo-response and its durability were studied.Results showed that the developed ?PFC exhibited good photo-response to the illumination and a rather stable long-term performance was attained.The effects of the methanol concentration,KOH concentration,light intensity and liquid flow rate on the cell performance were also studied.It was shown that increases of the methanol concentration,KOH concentration and light intensity were beneficial to the improvement of the cell performance.The cell performance firstly increased with increasing the liquid flow rate and then decreased with further increasing the liquid flow rate.More importantly,it was found that compared with the design of the oxygen-dissolved cathode,the achieved power density could be improved by 3~ 4 times.(3)A membraneless and monolithic ?PFC with a visible-light responsive photoanode and an air-breathing cathode was developed to realize the visible light utilization.The photo-response and its durability were studied.It was shown that the developed ?PFC was able to well respond to the illumination and a satisfactory durability was obtained.Parametric study was performed to study the effects of the methanol concentration,KOH concentration,light intensity and liquid flow rate on the cell performance.Results showed that the increases of methanol concentration,KOH concentration and light intensity were able to improve the cell performance.The increase of the liquid flow rate firstly led to the increased cell performance and then caused the cell performance to decrease.There was an optimal liquid flow rate generating the maximum power density.Compared with the UV light responsive anode,the power density of could be improved by 8~9 times.(4)A membraneless,monolithic ?PFC with dual visible-light responsive photoelectrodes and an air-breathing mode was developed to increase the solar energy utilization.The photo-response and its durability were studied.Experimental results showed that the developed ?PFC was able to well respond to the illumination and a rather stable long-term performance was attained.The effects of the methanol concentration,KOH concentration,light intensity and liquid flow rate on the cell performance were also studied.It was found that the increases of the methanol concentration,KOH concentration and light intensity were beneficial to the improvement of cell performance.Similarly,there also existed an optimal liquid flow rate resulting in the maximum power density. |
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