Enhancement Of Photo-Generated Charge Separation At Photoanodes Based On Defect/Synergy Strategy

Photoelectrochemistry（PEC）is not only an effective method to generate clean energy,but also an effective way to solve the current global energy and environmental crisis.Photoelectrocatalytic water splitting is an important part of solar energy applications,but it faces major bottlenecks,such as the severe compounding of photogenerated carriers that limits the performance of semiconductor photoelectrocatalysis.Among them,the transfer of holes is a relatively slow kinetic process compared with the photogenerated electron transfer process,so the transfer of holes plays a crucial role in charge separation.Therefore,it is necessary to effectively regulate the photogenerated holes in semiconductor photoelectrodes,and we realize the effective regulation of hole transfer by developing a new regulation strategy,and then realize the efficient separation of carriers to enhance the photoelectrocatalytic performance of photoelectrodes.The main research of this thesis is as follows:1.A new phosphorus vacancy modulation strategy was proposed for BiVO₄photoanodes.The phosphorus vacancy significantly inhibited the interfacial complexation of photogenerated carriers and enhanced the charge separation,thus greatly enhancing the photoelectrocatalytic performance of the composite photoanode.By modifying the cobalt phosphide derivative X-CDs-CoP（X=F,Cl）on the surface of BiVO₄,it was found that the electronic structure and catalytic activity of X-CoP were modulated after the introduction of phosphorus vacancies by NaBH₄reduction,which accelerated the transfer of holes to the co-catalyst CoP and inhibited the interfacial complexation of carriers.The prepared BV/X-CoP-Vp photoanode exhibited excellent water splitting performance,and the photocurrent reached 3.0 mA/cm²at 1.23 V_RHE.This work provides a new idea and method for the development of high solar energy conversion efficiency materials by defect engineering.2.Polymer related materials have been considered as ideal scaffolds for water splitting,providing more possibilities for developing the diversity of materials for photoelectrochemical（PEC）water splitting.Unfortunately,compared with other photoanode,the performance of polymer-based materials is far from satisfactory,so the development of new photoelectric materials is urgently needed.In this paper,a porphyrin phosphazene polymer（THPP-HCCP）was synthesized with a large conjugated structure,and Ag was modified on its surface to accelerate hole transfer and achieve efficient electron hole separation.Composites were deposited on the surface of BiVO₄（BV）to achieve effective PEC performance.We have deeply demonstrated the advantages of Ag-THPP-HCCP/BV heterostructures in a PEC water splitting system.Ag-THPP-HCCP accelerated the transfer of holes to the semiconductor surface to participate in the oxidation of water.This experiment provides a new method for designing novel photoelectrodes.3.Severe charge complexation and slow surface water oxidation kinetics severely limit the photoelectrochemical hydrolysis efficiency of ZnIn₂S₄photoanodes.In this paper,a composite photoanode with the introduction of sulfur vacancies（Vs）and Bi₂S₃in the ZnIn₂S₄photoanode was developed.Sulfur vacancies and Bisignificantly enhanced the PEC performance of the photoanode through a synergistic strategy,achieving a photocurrent density of 3.52 mA/cm²at 1.23 V compared to the reversible hydrogen electrode(V_RHE).an ABPE value of 0.7%was achieved.Kinetic and contact angle tests showed that the sulfur vacancies enhanced the kinetics of the oxygen precipitation reaction,which in turn improved the carrier separation.This work provides a new idea to enhance the performance of PEC water splitting by vacancy engineering.