【作者】 陈成；

【导师】 田维；

【作者基本信息】 苏州大学 ， 材料物理与化学， 2020， 硕士

【摘要】 近年来,化石能源短缺和环境污染的问题日益严峻,充分地开发利用可再生能源是解决这些问题的关键。光电化学(PEC)水分解制氢为太阳能到氢能的转化提供了切实可行的解决方案,实现了太阳能的有效利用,这也是解决能源危机最有希望的策略之一。PEC水分解包括三个主要过程:光生电荷的产生,光生电荷的分离与传输以及水的氧化还原反应。光阳极材料的合理设计对实现高效的PEC水分解系统至关重要。大多数金属硫化物由于具有较强的可见光吸收能力以及适合水氧化还原反应的能带位置,广泛地应用于PEC光阳极的研究。但是,由于光生载流子在传输过程中复合严重,限制了光阳极的PEC水分解性能。为了解决这些问题,本论文运用形貌调控、构筑异质结和掺杂的策略对光阳极进行了优化,制备了 Bi2WO6/TiO2/CdS和梯度氧掺杂In2S3/WO3两种复合光阳极。主要研究内容如下:(1)为了解决CdS材料中载流子复合严重和CdS颗粒与电解液接触不充分的问题。通过模板法,原子层沉积技术和微波水热法成功地在氟掺杂氧化锡的基底上合成了三维Bi2WO6/TiO2/CdS纳米片阵列,其中Bi2WO6多孔纳米片阵列材料作为支撑骨架以负载更多CdS颗粒,锐钛矿相的TiO2用作为能带匹配层以提高界面处电荷的分离效率,CdS用作为可见光吸收层。通过优化TiO2(8 nm最佳)的厚度,复合光阳极的光电流密度在1.23 V vs.RHE(相对于可逆氢电极的电位)处达到了4.91 mA cm-2,分别是CdS颗粒薄膜和Bi2WO6/CdS薄膜的3.1和2.1倍。PEC性能的提高可归因于材料比表面积的增加、光吸收能力的提高、以及电荷传输效率的提升。(2)为了解决In2S3体相光生电荷在传输过程中存在着复合严重的问题。通过水热法、水浴法和在聚乙烯吡咯烷酮溶液(PVP)中处理,成功设计并制备了具有梯度氧掺杂的WO3/In2S3复合光阳极。通过调控水浴反应时间和PVP处理时间,在三维WO3纳米墙上生长了具有最佳形貌和梯度氧掺杂的二维In2S3纳米片。这种设计结合了Ⅱ型结构和梯度能带结构的优势,促进了半导体中载流子的传输。此外,PVP处理提高了光阳极的载流子密度,延长了载流子寿命,并增加了表面活性位点,进而促进光阳极PEC性能的提高。最终,PVP处理3 h后,WO3/In2S3样品在1.23 V vs.RHE处光电流密度达到1.61 mAcm-2,是未处理的2.3倍。更多还原

【Abstract】 As the fossil energy shortage problem and environmental pollution become increasingly serious in recent years,the exploitation and utilization of renewable energy is the key to solving these problems.Photoelectrochemical(PEC)water splitting offers a feasible approach for solar-to-hydrogen conversion to achieve the effective utilization of solar energy,which is also one of the most promising strategies to solve the energy crisis PEC water splitting contains three main processes:generation of photogenerated charges,separation and transmission of photogenerated charges,and water redox reaction.The rational design and fabrication of suitable photoanode materials are crucial for achieving efficient PEC water splitting system.Most metal sulfides have been widely studied as typical PEC photoanodes,owing to their strong visible-light absorption and appropriate band position for water redox reaction.However,the severe recombination of photogenerated charges in semiconductors material during transmission limits its PEC performance.To solve these problems,we improved the PEC performance by the means of morphology control,construction of heterojunctions and doping.Finally,we design and facbricate 3D trilayer Bi2WO6/TiO2/CdS and oxygen gradient doped In2S3/WO3.The main research contents are as follows(1)In order to solve the problems of serious carrier recombination in CdS materials and insuff-icient contact between CdS particles and electrolyte,a 3D trilayer Bi2WO6/TiO2/CdS nanoflake array on fluorine-doped tin oxide substrates has been successfully synthesized by combining template method,atomic layer deposition technique and microwave-hydrothermal process,in which Bi2WO6 porous nanosheet nanoarray acts as skeleton to support more CdS particles,anatase TiO2 serves as a band-matching layer to improve the interfacial charge separation efficiency,CdS works as visible light absorber By optimizing the thickness of TiO2(8 nm best),the photocurrent density of the composite photoanode reaches 4.91 mA cm-2 at 1.23 V vs.reversible hydrogen electrode(RHE),which is 3.1 and 2.1 times that of CdS particle films and Bi2WO6/CdS films,respectively The enhancement of PEC performance is attributed to the enlarged surface area,increased light harvesting ability,and improved charge transport efficiency(2)To address the serious charge recombination of In2S3 bulk phase,the gradient oxygen doped WO3/In2S3 heterostructure photoanode has been successfully designed and synthesized by combining hydrothermal,water bath process and polyvinylpyrrolidone(PVP)solution treatment.By varying the water bath reaction time and PVP treatment time,2D In2S3 nanosheets are grown on the 3D WO3 nanowalls with the optimal morphology and gradient oxygen doping.Such design takes the advantage of both type Ⅱ and gradient band structure to facilitate the bulk carrier transport.Furthermore,the PVP treatment enhances carrier density,prolongs carrier lifetime,and increases surface active sites,thereby promoting the improvement of the PEC performance of photoanode.Finally,after 3 hours of PVP treatment,the photocurrent density of WO3/In2S3 photoanode reaches 1.61 mA cm-2 at 1.23 V vs.RHE,which is 2.3 times that of untreated sample.更多还原