光电催化还原Cr(VI)用层级多孔Bi2O3纳米片薄膜电极的原位自组装及性能调控

In order to solve the problem of low solar energy utilization efficiency and the risk of secondary pollution in photo(electro)catalytic method for heavy metal removal, this project proposed a noval Bi2O3 based photoelectrochemical system for photoelectrocatalytic reduction of Cr (VI), as Bi2O3 has the advantages of adjustable band gap,proper energy band structure and environmental friendly.. .The project intends to employ the low-cost, simple chemical bath deposition method to self-assemble the hierarchical porous Bi2O3 nanoplate thin films, and study the crystallization kinetics of self-assemble process to freely control of morphology and structure of the materials; By preparing the CQDs/n-Bi2O3 composite photoanode, the CQDs was used to improve the solar energy utilization efficiency and photostability of the photoanode; The conductivity type of Bi2O3 was regulated through Cu and N doping, thus p-Bi2O3 was produced as a photocathode for photoelectrocatalytic reduction of Cr(VI); The generation, transmission, separation and recombination mechanisms of minority carriers were investigated to determine the ideal structure and composition of photoelectrodes, to optimum the structure of photoelectrochemical cell, and to form the prototypes of synthesizing hierarchical porous Bi2O3 nanoplate thin solid film electrode. .The achievement of the project will provide significant theoretical and practical guidance for developing new photovoltaic and photoelectrochemical catalytic electrode materials, to solve the problem of water pollution elimination, and opening up new ways for environmental governance.

项目提出利用Bi2O3带隙可调、能带结构合适和环境友好的特点，构建光电催化还原Cr(VI)用Bi2O3基光电化学池，解决现行光（电）催化法治理重金属废水存在的太阳能利用效率低和二次污染等问题。.项目拟采用成本低廉、简单易行的化学水浴法自组装制备层级多孔Bi2O3纳米片薄膜，研究自组装过程的结晶动力学，实现材料形貌与结构的自由调控；通过CQDs敏化制备CQDs/n-Bi2O3复合光阳极，提高光阳极的太阳能利用效率及光稳定性；通过Cu和N掺杂对Bi2O3的导电类型进行调控，制备p-Bi2O3作为光电催化还原Cr(VI)用光阴极；研究少子的产生、传输、分离及复合机制，确定光电极的理想结构与组成，优化光电化学池结构，形成层级多孔Bi2O3纳米片基薄膜电极的制备技术原型。.项目成果对于开发新型光电催化电极材料，解决当前水体污染治理问题，开辟环境治理的新途径具有十分重要的理论与实际指导意义。

光电催化是一种将太阳能直接转换为化学能的太阳能利用新技术，是解决当今社会面临的能源和环境问题有效途径之一。铋系半导体材料具有合适的能带结构且带隙较窄、组成元素丰富无毒、稳定性较好，是极具发展前景的光电极材料之一。. 本项目创新性的提出对层级多孔Bi2O3纳米片薄膜电极的原位自组装及性能调控，并应用于光电催化还原Cr(Ⅵ)。项目主要研究了层级多孔Bi2O3纳米片薄膜电极的原位自组装及反应机理，通过调节工艺参数优化了Bi2O3纳米片薄膜的成分、结构和形貌等，揭示了层级多孔Bi2O3薄膜是异相形核和Ostwald熟化共同作用的结果，并获得了薄膜制备技术原型；采用水热反应法制备了CQDs，通过PDDA预处理提高CQDs与Bi2O3的结合，获得了CQDs/n-Bi2O3复合光电极，使光阳极性能得到提升；采用连续离子层吸附反应法在层级多孔Bi2O3薄膜表面原位负载了Bi2S3光敏剂，获得了Bi2S3/n-Bi2O3复合光电极，其光电流密度达到5.5mA/cm2，在750s内(0.5V-2.0Vvs.RHE)可保持稳定；研究了掺杂N元素对Bi2O3的导电类型以及成分、结构和形貌的影响规律，在不破坏薄膜形貌的前提下成功实现了层级多孔Bi2O3纳米片薄膜导电类型向P型的转变；使用旋涂法制备出CuBi2O4薄膜，通过在半封闭环境下对铋酸铜薄膜进行退火制造氧空位，使得薄膜电极的光电化学性能得到提升，在0.05Vvs.RHE时光电流密度可达-400μA/cm2；通过将Bi2O3纳米片薄膜进行硫化退火成功制备出了Bi2S3纳米片薄膜，并通过二次退火调控了其缺陷，使其光电流密度在1.23Vvs.RHE时接近3.5mA/cm2，是纯Bi2S3薄膜光阳极的最高纪录；最后，以Bi2S3薄膜做光阳极组装了光电化学池进行Cr(Ⅵ)的光降解，通过加入一定量的Na2SO4作为电解质，以及一定浓度的甲酸作为空穴消耗剂，当Cr(Ⅵ)浓度为50mg/L时，60min内还原率可达91.43%。