Manipulation On The Charge Transfer Kinetics Of Photoelectrochemical Cells

Photoelectrochemical cells(PEC cells)can directly convert solar energy into chemical or electrical energy through photoelectric catalytic oxidation-reduction reactions,and become a key means to solve the intermittentness of solar energy.Artificial photosynthesis cells can convert solar energy into chemical materials by splitting water and reducing carbon dioxide.The solar powered PEC cells can directly convert solar energy into electric energy through photocatalytic conversion of renewable redox couples,which can convert,storage and distrute solar energy in a single device.In the PEC process,the excition of electron and holes,the separation and transporation of charge,and the redox reaction on the surface was finished by the charge transfer such as a relay race.However,how to effectively control the charge transfer kinetics is a difficult problem for the further development of photoelectrochemical cells.Toward this end,this paper proposes to optimize the charge transfer dynamics to control the performance of photoelectrochemical cells to achieve higher solar energy conversion efficiency.Works in this paper can be mainly divided into the following parts:1.During the preparation of TiO2,adjusting of the TiO2 nano rod micro-structure is achieved by the way of the "salt-treated",tunning the hydrothermal time and the calcination temperature.The PEC water splitting performance of the optimized TiO2 photoelectrode was optimized.Under AM 1.5 G illumination,the photocurrent density of the optimized TiO2 photoanode(TNa22-550)under 1.23 V vs.RHE is 1.87 mA cm-2.Through in-situ TPV measurement,the charge transfer kinetics of the TiO2 photoelectrode and the photoelectrode-electrolyte interface are unmasked.In addition,using the in-situ TPV combined with the logic tree algorithm,the influence of the micro structure regulation on the TiO2 photoelectrode with the charge transport and recombination and the effection of the charge transport and recombination kinetics on the PEC performance of the TiO2 photoelectrode were explored.2.The C,N and S co-doped TiO2 photoanode is prepared through a simple thermal diffusion method.The PEC performance of doped TiO2 photoanode was optimized.Under AM 1.5 G illumination,the photocurrent density of the C,N and S co-doped TiO2 photoanode(TTCNS-125)under 1.23 V vs.RHE bias is 3.95 mA cm-2.On the view of photophysics,the co-doping of non-metallic C,N,and S improves the light absorption performance of the TiO2 photoanode;on the view of charge transport dynamics,the codoping of non-metallic C,N,and S optimizes the TiO2 photoanode-electrolyte charge transfer kinetics.In addition,combined with physical characterization,PEC performance and in-situ TPV measurement,the analyzes of the relationship of light absorption,separation and transporation of charges,and the redox reaction was unmasked.3.Adjust the performance of photoelectrochemical cells by constructing p-n heterojunction interface.In the iodine-based SPEC system,the p-type semiconductor bismuth oxyiodide wrapped n-type titanium dioxide TiO2(FTO/TiO2@BiOI)is used as a photoanode,and lithium iodide is used as a renewable redox active material.From the perspective of interface charge transfer kinetics,the p-n heterojunction interface can effectively control the unidirectional charge transfer,and prevent photo-generated electrons from being oxidized by the cathodic redox mediator and being captured at the"electrode-electrolyte" interface,resulting in back electron transfer and darkening.Current.In addition,the oxidative active medium I-/I3’ exhibits p-type characteristics,which plays an important role in reducing the dark current caused by interface trapping.Under AM 1.5 G illumination,the photocurrent density can reach 3.4 mA cm-2.Further use the in-situ TPV measurement to reveal the charge transport kinetics at the photoanodeelectrolyte interface.4.Comstructing the unbiased Z-scheme SPEC by combining BiVO4 photoanode with Cu2O photocathode(conduction band position is about-1.1 eV).At the same time,Fc-bipy3+is used as the bipolar electrolyte to achieve a discharge voltage of 0.67 V while preventing cross-contamination of the electrolyte in Z-scheme SPEC.Systematically optimize the charge transfer kinetics of the photoelectrode and the photoelectrodeelectrolyte interface to achieve higher photoelectric conversion efficiency.The initial photocurrent density is 2.4 mA cm-2,and maintained at 1.8 mA cm-2.5.The final work was focused on the control the side reaction of photo-excited charge injection by optimizing the solid-state interface,it is the first time to design and construct an all-in one,solid-state SPEC.Bismuth vanadate was used as the photoanode,LiBr/PAM hydrogel was used as the electrolyte,cathode-active mediator and separator,and Prussian blue was used as the negative electrode material.As an electrolyte,LiBr/PAM hydrogel contains both the positive electrode active material and the electrolyte.Importantly,the performance of SPEC is effectively improved by optimizing the interface charge transfer kinetics.