Controllable Construction And Photoelectrochemical Performance Of Highly Efficient Photoelectrode Materials

As the key techniques to utilize solar energy,dye-sensitized solar cells(DSSCs)and photoelectrochemical(PEC)technology can convert the most abundant solar energy into clean energy,such as electric energy and hydrogen energy,which provide the possibility to alleviate the two major problems of environmental pollution and energy crisis.The quality of the semiconductor electrode materials is the key to determine their solar catalysis/conversion performance.Domestic and foreign scholars have done a lot of research work and made great progress in developing and designing semiconductor materials for photoelectric catalysis/conversion with excellent performance.However,the technical methods and theoretical basis for effectively improving photoelectric catalysis/conversion performance still need to be fully explored and deeply revealed,and there is still a long way to go from laboratory to industrial-scale application.Therefore,designing and constructing semiconductor materials with excellent properties is an important research content in the field of photoelectric catalysis/conversion.Titanium dioxide(TiO₂)and tin dioxide(SnO₂)have the characteristics of stable structure and abundant earth reserves,enabling them great potential for photoelectric catalysis/conversion.However,the wide bandgap and slow surface catalytic reaction kinetics limit their performance in photoelectric catalysis/conversion.The present dissertation focuses on the basic scientific issues involving the structural design,controllable preparation,performance and mechanism research of high-performance TiO₂ and SnO₂ based semiconductor materials.The purpose is to enhance the photoelectric catalysis/transformation performance of TiO₂ and SnO₂ based composite semiconductor materials,and to enrich the technical methods and theoretical understanding for improving the photoelectric catalysis/conversion performance.The main nolvelty and conclusions are as follows:(1)Au-decorated TiO₂ hollow submicron spheres were fabricated by a facile template-free solvothermal process in combination with a subsequent in situ reduction.The plasmon-enhanced effect of precious metal Au is beneficial to improve the visible light utilization ability of TiO₂,while the unique hollow structure owns excellent light scattering effect.Benefiting from the collaborative advantages of Au and hollow structure,the DSSCs based on the Au/TiO₂ composite exhibit excellent photoelectric conversion performance.Under the illumination of the standard AM1.5G simulated sunlight(100 mW cm^-2),the power conversion efficiency(PCE)of the device is up to7.3%,which is an improvement of 37.7%compared to the device based on P25 TiO₂.(2)A simple two-step hydrothermal method was developed to prepare the TiO₂/NiTiO₃ composite nanorod arrays on a conductive FTO substrate.This unique three-dimensional ordered heterostructure can broaden the spectral response range of TiO₂,promote separation and transformation of photogenerated carriers,and accelerate the diffusion rate of electrolyte ions.Under standard AM1.5G simulated sunlight(100 mW cm^-2)irradiation,the TiO₂/NiTiO₃ hybrid shows obviously higher PCE and fill factor than the pristine TiO₂.In addition,the heterostructured TiO₂/NiTiO₃ demonstrates excellent structural stability compared with organic dye N719 sensitized TiO₂ solar cells.(3)Hollow microfiber TiN/N-TiO₂woven cloth with nanorod-array structure was fabricated by a facile hydrothermal-nitridation process.Firstly,the plasma enhancement effect of TiN and the light scattering characteristics of hollow fiber structure can improve the utilization of sunlight;Secondly,the ammonia atmosphere treatment is beneficial to enhance the electrical conductivity of materials,thus improving the efficiency of charge separation and transport;Finally,the abundant oxygen defects provide active sites for surface catalytic reactions and enhance the water oxidation kinetics.As a result,under simulated light(100 mW cm^-2)illumination,the photocurrent density of TiN/N-TiO₂ self-supporting electrode with hierarchical structure is as high as 3.12 mA cm^-2 at 1.23 V vs.RHE without obvious degradation after 10 h test.In addition,the electrode also substantiates outstanding visible-light-driven photoelectrochemical performance(1.63 mA cm^-2)without the use of any hole scavenger and cocatalysts.(4)Sn/SnO_2-x composite nanotubes with pea-pod like structure were firstly fabricated via an electrospinning-hydrogenation process.The plasmon enhancement effect of non-noble metal Sncan improve the visible light absorption ability;the contaction between Snand SnO₂ are of great benefit in promoting charge carrier separation and the introduced oxygen vacancies are favorable for accelerating surface catalytic oxygen evolution reaction kinetics.Benefiting from the synergistic effect of the nanotube structure,metallic Snand the oxygen defects,the material demonstrates a significantly enhanced performance.Under simulated light(100 mW cm^-2)illumination,with the applied bias of 1.23 V vs.RHE,the Sn/SnO_2-x delivers a high photocurrent density of 245?A cm^-2,which is four times higher than that of pristine SnO₂.