Optimization Of Titanium Dioxide Photoanode System And Application In Hydrogen Production By Solar Energy Photoelectrochemical Water Splitting

With a ceaselessly increasing attention toward solar-to-hydrogen?STH?conversion,photoelectrochemical?PEC?device for hydrogen production technology have made huge step forward for address energy resource shortage and energy consumption.Research and development of efficient and stable photoelectrodes that are capable of harvesting visible light for an optimized use of solar energy are very prerequisite in hydrogen production process by PEC water splitting.As a good candidate of semiconductor photoelectrode materials,Titanium Dioxide?TiO₂?has many advantages,such as their high photocatalytic activity,long-term stability,low cost and easy accessibility.Simultaneously,the most pronounced disadvantage of TiO₂ of its poor response to ultraviolet?UV?light?only about 5% of sunlight?and recombination of photogenerated electrons and holes,so the poor performance of bare TiO₂ photoelectrodes has limit its industrial applications.Numerous methods have been employed to enhance theoverall PEC efficiency of TiO₂ photoeletrode,which was resolved by depressing the recombination of photogenerated electrons and holes in the hydrogen production process by PEC water splitting.The above methods can be best exemplified by optimizing the anode with noble metal modification,defect implantation,loaded polymer materials and element doping.Based on above research background,this thesis presents the following three kinds of TiO 2 photoelectrode optimization plan to achieve novel high-performance PEC system:?1?Au@CdS/RGO/TiO₂ photoelectrode were synthesized via various methods.The unique heterostructures of the Au@CdS/RGO/TiO₂ photoelectrode were confirmed by SEM,TEM,Raman and XPS characterization methods.Au@CdS nanoparticles with core–shell structure were introduced into the TiO₂ photoelectrode for the first time,and the Au@CdS nanoparticles could endow the TiO₂ photoelectrode with both visible light response ability and the plasmonic property.Moreover,the RGO thin film sandwiched between TiO₂ nanorod and Au@CdS core–shell nanoparticles played an important role in the fast transport of photogenerated charges.?2?We deposited the plasmonic Bi nanoparticles on BiOCl nanosheets?Bi/BiOCl?via insitu photoelectroreduction,and Bi/BiOCl as the photocathode enabled solar water splitting in a TiO₂–Bi/BiOCl PEC system.Meanwhile,we explored to understand the relationship between the PEC performance and the composite ratio of Bi/BiOCl,and the density functional theory calculation results show that charges obviously transfer from the Bi cluster to the BiOCl?001?surface.The structure of Bi/BiOCl photocathode has been successful y optimized,according to the current–potential curves and charge injection efficiency.The highly enhanced PEC water splitting activity could be attributed to the dual roles of Bi nanoparticles in enhancing the charge transfer and surface plasmon resonance?SPR?effect.?3?In order to improve the utilization ratio of sunlight and stability of photoelectrode,the organic polymer?poly-dopamine: PDA?was further applied to sensitize TiO₂ electrode.In this system,the Bi-AgIn5S8 is first loaded on TiO₂ photoelectrode to achieve a visible light responsibility.The TiO₂/TiO₂/Bi-AgIn5S8/PDA heterostructure photoelectrode was further prepared by hydrothermal method.The mechanism of PECwater splitting over heterostructure photoelectrode was investigated,and some factors that affected the PEC conversion efficiency were also analyzed.