Aqueous Solar-charged Redox Flow Cell Based On TiO₂ Photoanode

Using photochemeical cell to realize water splitting to provide energy is still faced with many problems.One is the storage and transportation of hydrogen,and another one is the low conversion efficiency.Solar-charged redox flow cell via direct integration of a photoanode can be a possible approach to achieve dual function of conversion and storage of solar energy.TiO₂ has been widely used as photoanode in the field of photochemeical water splitting with stable performance.Also,different redox active materials can provide the space for the design of solar-charged redox cell.In this thesis,we successfully designed and fabricated an solar-charged redox cell device with the dual function of conversion and storage of solar energy via direct integration of a photoanode into a redox flow cell using highly water-soluble Br₂/Br^-and I₃^-/I^-redox couples as the energy carriers.In the second section of this thesis,we adopted the hydrothermal method to prepare the TiO₂ photoanode with one-dimentional nanostructure,and then investigated the properties of photochemeical water splitting.The results showed that the TiO₂ nanoarry was rutile phase and saturated photocurrent density could reach to 0.6 mA·cm^-2,corresponded to the value reported.Then in the third section of this thesis,we invesitigated the electrochemical properties of the redox couples of Br^-/Br₂、I^-/I₃^-、Cu²⁺/Cu and[Fe（EDTA）]²⁺/[Fe（EDTA）]³⁺.The redox potential、diffusion coefficient and reaction rate constant were the same as the values reported.The we tested the cycle performance of the halfcell using[Fe（EDTA）]²⁺/[Fe（EDTA）]³⁺与Li/Li⁺as the redox couples.In the 50 cycles,the capacity of the cell didn’t show any decrease.Then we used Br^-/Br₂ as the cathode material and I^-/I₃^-、Cu²⁺/Cu and[Fe（EDTA）]²⁺/[Fe（EDTA）]³⁺as the anode materials separately to compose the full batteries.All the cells showed stable cycle performance.Then we studied the performance of the solar-charged redox cell using TiO₂ as the photoanode.The cells were charged under 1 sun illumination and discharged by the electrochemical way.The current density-potential curve was similar with the photochemical water splitting.During the ten cycles,the cell maintained stable photocurrent density and discharge capacity.Solar–chemical–electricity energy conversion efficiency of the cell using Br^-/Br₂和I^-/I₃^-as the cathode and anode redox couples was calculated to be ca.0.16%.In the fifth section of this thesis,we adopted the solvothermal method to prepare the Bi₂WO₆ electrode assembled with microflower arrays and further synthetized nanoporous Bi VO₄/WO₃ electrode.The photocurrent density was 5 mA·cm^-22 when BiVO₄/WO₃ electrode was adopted to oxidize sulfite.When BiVO₄/WO₃ electrode was used to oxidize Br^-and reduce I₃^-,the solar conversion efficiency can reach to 2.63%。...