Study On The Surface And Interface Regulation Of Electrocatalytic And Photoanode Materials For Oxygen Evolution Reaction And Their Performance For Water Splitting

With the rapid development of society,the demand for energy has become more and more serious.At present,the main energy that we used is non-renewable fossil energy.However,such energy sources are not only have non-renewable nature,but also cause serious environmental pollution after their use.So that they cannot always be the main energy source for human beings.Thus the development of new energy sources has become an urgent task.Among many new energy sources,hydrogen energy is an ideal new energy source due to its high energy density,clean and environmentally friendly combustion products,and diverse storage methods.The two hydrogen production methods,electrocatalytic water splitting and photoelectrochemical(PEC)water splitting have become the most promising hydrogen production methods owing to their cheap and abundant energy sources,clean and pollution-free products.However,the oxygen evolution reaction(OER),which is the half reaction of water splitting,requires a much higher overpotential due to the transfer of multiple electrons and the dynamic slow reaction kinetics,which slows down the whole reaction process and becomes the bottleneck of water splitting.Therefore,research and design of efficient and stable water oxidation catalysts to increase the rate of OER have become an important issue in the promotion of electrocatalytic water splitting and PEC water splittingCatalytic reactions carried out at the surface and interface of the catalysts,so the interface state and properties of catalysts have important effects on the catalytic performance of materials.Therefore,regulating the surface and interface of the catalyst is an important means to optimizing the catalytic performance of the catalysts Therefore,this thesis is starting from the regulation of the surface and interface of the catalysts,which adopts the method of constructing composite materials to effectively improve the catalytic efficiency of electrocatalytic and photoelectrocatalytic materials.The specific research contents are as followsIn the first chapter,the background meaning and preparation methods of hydrogen energy are briefly introduced,and the basic principles and performance parameters of the two most advantageous preparation methods,electrocatalytic water splitting and PEC water splitting,are systematically introduced.Then,the restriction of OER on water splitting reaction is analyzed,and by analyzing the current research status of electrocatalytic and photoelectrocatalytic OER catalysts,the surface and interface strategy of improving catalytic performance of electrocatalytic and photoelectrocatalytic OER catalyst is summarized,and the topic significance.Finally,the research content of this paper are introduced.In chapter 2,the preparation,characterization and electrocatalytic properties of CeCO3OH/NiFe LDHs composites were studied.CeCO3OH/NiFe LDHs composite was synthesized by two-step hydrothermal method.Tests showed that the CeCO3OH/NiFe LDHs electrode had better OER catalytic performance than a single NiFe LDHs or CeCO3OH.We have found that this is because the CeCO3OH/NiFe LDHs composites exist a Ce3+(?)Ce4+conversion process,it can provide a short ion diffusion path to the composite,so that can promote the rapid diffusion of oxygen and electronic transmission.Besides,the ESCA of CeCO3OH/NiFe LDHs composites also increased,indicating that the reactive sites of the composites increased.This is due to the Mosaic structure between CeCO3OH nanosphere and NiFe LDHs nanometer sheet,which effectively reduces the agglomeration of LDHs nanometer sheet and reduces the loss ofactive sites caused by agglomeration.The experimental results show that the synergistic effect of CeCO3OH and NiFe LDHs can effectively improve the properties of the surface and interface of NiFe LDHs,thus improving the OER catalytic performance of NiFe LDHs.In chapter 3,We synthesized a new Ir organic water oxidation catalyst IrL1(Cp*)Cl with strong electron-donating and hydrophobic group,and used it as a catalyst to load it on BiVO4 and Ti/Fe2O3 by simple physical adsorption.Due to its hydrophobicity,this catalyst has quite good stability in water medium.Compared with other water-soluble water oxidation catalysts,it does not need to add a protective layer.The stability test shows that this catalyst has relatively good stability in neutral solution and PH=14 alkali solution.The test shows that the load of the cocatalyst IrL1(Cp*)Cl effectively improves the photoelectrocatalytic performance of the photoanode.When the bias pressure is 1.23v vs RHE,the current density of IrL1(Cp*)Cl/BiVO4 and IrL1(Cp*)Cl/Ti/Fe2O3 can reach 1.58mA/cm2 and 2.26mA/cm2,which are 2.6 times and 1.67 times than that of the original BiVO4 and Ti/Fe2O3 photoanode.Further study shows that the the interfacial separation efficiency of the composite photoanode reached 60%and 91%respectively,which indicated that the load of the cocatalyst greatly reduced the carrier recombination problem at the interface,and thus improved the photoelectric conversion efficiency of the photoanode.In addition,the light stability test of composite photoanode shows that the stability of BiVO4 and Ti/Fe2O3 photoanode has been greatly improved after the supported cocatalyst,which proves that IrL1(Cp*)CI can be used as a protective layer to improve the photocorrosion resistance of the material.In summary,the synergistic effect of composite materials can effectively improve the catalytic efficiency of electrocatalytic and photoelectrocatalytic OER catalysis,improve the reaction efficiency of the water oxidation half reaction in the water splitting,and then promote the efficiency of the electrocatalytic and photoelectrocatalytic water splitting.