One-dimensional TiO₂ And G-C₃N₄ Photocatalysts Forphotoelectrochemical Application

With the increasing of populaiton and development of social economy,It's foreseeable that the limited fossil energy will be depleted.Besides,some negative effects of COx,NOx,SOx and soot which come from the fossil fuel burning have brought a series of problems,such as greenhouse effect,acid rain corrosion and air pollution.All of this problems not only make a threat to human's survival,but becoming a problem that we have to be solved.Therefor,It's our duty and a great challenge for us to solve the issue of pollution and energy depletion as well as exploiting some green new energy to replace the fossil energy that we lived on.However,hydrogen as a kind of clean and environmentally friendly energy which is no doubt becoming people's first choice.It's common recognized that hydrogen as the final clean energy carrier will play an important role in our furture production and Life.So,how to effectly convert solar energy into power and use the power to split water into hydrogen has become a hotspot for the scientist to research.In 1972,the pioneer work for Fujishima and Honda who used TiO₂ as an electrode to photocatalitic decomposition of water has creating a new path.In the process of photocatalytic,several low cost materials can be used as electrode.In this paper,we make some research about titanium dioxide and carbon nitride,especially their utilization of photoelectrochemcial water splitting.This thesis can divide into three parts,details are as follows:1.The photocatalytic performance research of phosphorus doped carbon nitride/titanium dioxide heterojunctionFirst,we prapared rutile TiO₂ by the method of hydrothermal synthesis and made an optimization of the synthetic conditions as well as annealing conditions.In order to improve the visible light activity and widen the spectral range,a modified method has been utilized to increase the activity by using a stable organic semiconductor materials carbon nitride.The electron injection of this material which has large conjugate ? bond enable them have the visible light activity,then surface hybridization facilitates the migration of hole and inhibits recombination of photogenerated carriers.In this case,we used phosphorus element doping our photocatalytic materials to improve its performance.It's found that doping with non-metallic phosphorus element can effectively change the original band of our materials and narrow the band gap.So,this method greatly improved titanium dioxide's visible light activity and provide a new idea for us to widen some UV-responsive semiconductor materials.2.3D Bi₂MoO₆ nanosheet/W-doped TiO₂ nanowires heterostructure: enhanced photocatalytic activities and photoelectochemistry performanceHydrothermal method was also used to prepare vertically aligned rutile TiO₂ nanorod arrays and then synthesized W-doped TiO₂ nanowires using a simultaneous hydrothermal etching and doping in a weakly alkaline condition.A serious of photoelectrochemical characterization,testing show that the method can introduce a impurity level in the band gap of TiO₂ which decreased the recombination probability of photogenerated electron-hole and improved the photocatalytic activity of it.Inspired by the natural plant photosynthesis,3D heterojunction materials have been constructed by electrophoretic deposition bismuth molybdate nanosheet on the surface of 1D TiO₂ nanowires.The advantage of high visible light activity for bismuth molybdate and unique morphological structure of composites can widen the absorbance range as well as facilitate the electron transfer rate,so,an excellent photocatalytic efficiency can be achieved.3.Plasmonic-metal Au nanorods/carbon nitride composites' photocatalytic activity for photoelectrochemcial water splittingIn this section,we synthesized precious metal gold nanorods by seed-mediated growth method,then Au/g-C₃N₄ nanocomposites has been prepared through one pot way.SEM,XRD and FT-IR are utilized to characterize our materials,afterwards,a series of electrochemical characterization are conducted by I-t curve,EIS,etc.We discovered that the Au/g-C₃N₄ composites exhibited excellent photocurrent.This is mainly attributed to the SPR effect on the surface of Au nanorods and the good electronic capture capability.So,the photocatalytic activity of carbon nitride under visible light presents a great promotion.Calculation shows that combine Au nanorods with carbon nitride can effectly decrease the band gap of the semiconductor materials and widen the absorbance range.Therefor,this experiment has a profound significance for researching the relationship between Co-catalyst and catalytic activity.