| Seeking for sustainable energy is one of the most significant challenges in our modern society. The use of fossil energy resources has produced massive amount of pollution, destroys our environment and reduces the natural resources in the earth. Thus, it is necessary to find an alternative energy to the fossil fuel. Solar energy is recognized to be an ideal choice for the convenient, green and sustainable energy for the future. In the past decades, in addition to the Si photovoltaic cell, dye-sensitized solar cells (DSSC) have attracted much attention due to their advantages of efficiency, price and technological simplicity. However, solar energy is hardly to store because of its dispersity and intermittency, which limits its application in our daily life. Innovative solar storage technologies are urgently needed to meet the fast-growing demand for solar energy usage. In this thesis, we tried to explore an innovative light-electric-chemic conversion and storage system based on DSSC. In this system, solar energy could be directly converted to chemical energy, which could also be stored as redox-active electrolytes. In addition, we tried to design a photo-assisted fuel cell (PFC) based on photooxidation of organic pollutants, which can realize the sewage purification and power generation at the same time. The main results in this work are summarized as follows:1. A novel solar-rechargeable battery (SRB) was proposed and constructed by combining a bi-functional photo-electrode and an electron-storage counter electrode together. The bi-functional photo-electrode was fabricated by hybridizing a dye-sensitized TiO2photo-anode with a hole-storage electrode (poly (3,4-ethylenedioxythiophene), PEDOT), which can convert solar energy to electrical energy and store holes as well. And the counter electrode was consisted of ClO4-doped polypyrrole (PPy). The SRB cell can be photocharged at illumination for120s, and then electrochemically discharged at a constant current of8μA cm-2in the dark. After10cycles of charge-discharge, the discharging capacity maintained at5mAh g-1without decay. The results indicate that the SRB can realize a direct conversion and storage of solar energy into chemical energy.2. A solar-rechargeable redox flow battery (SRFB) was fabricated, which integrates solar sorption, photo-induced charge separation, and simultaneous regeneration of redox couples in a two-chambered cell, enabling solar energy to be stored as cathode-and anode-active solutions (chemical energy) separately in a controlled fashion for deferral redox flow battery applications. Here, I3-/I and DMFc+/DMFc (Decamethylferrocene) was used as the active electrolytes. The SRFB was photo charged for2400s. and then discharged at a constant current of30μAcm-2to0.1V in the dark, after10cycles of charge-discharge, the discharging capacity maintains at19.5mAh g-1with acceptable decay. The TEMPO+/TEMPO (2,2,6,6-TetramethylpiperidinE) and BQ/BQ-(1,4-benzoquinone) redox couples can also realize the solar-electric-chemical energy conversion and storage. This device has realized direct conversion of solar energy to electrical energy and made the large scale solar-chemical energy storage possible if the electrolytes are stored in large tanks.3. A photo-assisted fuel cell (PFC) was constructed by a dye-sensitized TiO2photo-anode and an air-cathode using a methyl orange (MO) aqueous solution as the target pollutant. In our experiment, under40mW cm-2light intensity,20mg L-1MO aqueous solution was used as the electrolyte. The PFC discharge at a constant current of50μA cm-2at0.1V. After120mins of illumination, the degradation ratio of MO reached up to98%. The dye-sensitized TiO2photo-anode made the pollutant degradation more efficiently and durably ascompared with the conventional TiO2power catalyst because of the wide absorption range of the dye and the confirm structure of the device. The air-electrode ensures the fast consumption of the electrons from the photo-anode, which also enhance the overall efficiency. In this device, we realized the sewage purification and power generation at the same time. |
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