光阳极复合结构设计及其光电催化水氧化性能与机制研究

发布时间：2018-05-09 20:44

本文选题：光电催化 + 光阳极　；参考：《北京化工大学》2015年硕士论文

【摘要】：为解决传统能源的日渐短缺和其使用时对环境产生的污染和危害,利用清洁能源如太阳能光解水制氢或二氧化碳还原得到碳氢燃料是一个重要途径。在水分解反应中,水氧化半反应具有高的反应势垒,且需要同时转移4个电子(伴随质子耦合过程),成为水分解的瓶颈,因此设计高效、功能耦合的光阳极具有重要意义。光阳极的设计面临许多制约其性能的关键问题,例如：光阳极表面水氧化反应速率慢、电子-空穴容易发生表面复合、体相电子-空穴的分离效率低等。本工作从设计复合结构(如：核/壳结构、异质结构)光阳极入手,利用双金属氢氧化物的催化与光吸收性质实现光阳极的性能强化,取得主要研究结果如下：1.发展了光辅助电沉积法在TiO2纳米阵列光阳极上构建磷酸化双金属氢氧化物@TiO：核-壳结构光阳极,该方法获得的修饰层具有超薄(≈10nm)、均匀覆盖的特点。将其用于光电催化水氧化反应,光电流起始电位较TiO2显著降低约200 mV,在1-1.8 V的氧化效率高达100%。这是由于双功能修饰壳层同时抑制了表面电子—空穴复合与电子参与的氧还原逆反应,从而增强了光生电荷分离,提高了氧化效率2.在BiVO4光阳极的表面生长了双金属氢氧化物(LDH)纳米墙网络结构,构筑了新型LDH@BiVO4复合光阳极,LDH二维纳米片以垂直BiVO4表面交错生长为纳米墙结构。复合光阳极的光电流起始电位较单纯BiVO4显著降低610 mV,且光电转化效率(IPCE)和氧化效率明显提升。这首先是因为LDH的催化作用提升了表面水氧化反应速率,且二维纳米片交错形成的网络减小了光生空穴扩散距离；另外,BiVO4与LDH的带隙及相对能级关系,使其可提高对可见光的吸收。该研究为催化/光敏/二维结构三重性质耦合的复合光阳极设计提供了思路。3.发展了以Zn2+为添加剂对BiVO4光阳极形貌和尺寸进行调控的方法,得到了不同粒径、颗粒孔隙、表面粗糙度的BiVO4光阳极,结构优化的BiVO4的光电流在1.23 V时提高了3倍,这是由于调控的BiVO4具有更高的表面粗糙度以及更小的颗粒尺寸,有利于体相电荷的分离。该工作利用低价、无毒的锌离子作为添加剂,在生长阶段对BiVO4结构进行控制,且不影响其组成,是一种调控光阳极尺寸、形貌的简便、有效方法。
[Abstract]:In order to solve the increasing shortage of traditional energy and the pollution and harm to the environment in its use, it is an important way to make hydrogen by using clean energy, such as solar photolysis and carbon dioxide reduction. In the water decomposition reaction, the semi reaction of water oxidation has a high reaction barrier and 4 electrons are transferred at the same time. The design of efficient and functional coupling of the photo anode is of great significance. The design of the photo anode is faced with many key problems that restrict its performance, such as the slow reaction rate of the surface of the anodic surface of the photo anode, the surface recombination of the electron hole easily and the low separation efficiency of the body phase electron hole. The performance enhancement of the photo anode was achieved by using the composite structure (such as nuclear / shell structure, heterostructure) and the photocatalytic and optical absorption properties of bimetal hydroxide. The main results were as follows: 1. the phosphorylated bimetallic hydroxide @TiO was constructed by optical assisted electrodeposition on the TiO2 nanowire anode. The nucleation and shell structure photoanode, the modified layer obtained by this method has the characteristics of ultra thin (10nm) and uniform coverage. It is used for the photoelectrochemical catalytic water oxidation. The initial potential of the photocurrent is reduced by about 200 mV compared with TiO2, and the oxidation efficiency of 1-1.8 V is as high as 100%.. This is due to the simultaneous inhibition of the surface electron hole recombination with the double functional modified shell. The oxygen reduction inverse reaction of electronic participation enhanced the separation of light generated charge and increased the oxidation efficiency of 2. on the surface of the BiVO4 photoanode. The new LDH@BiVO4 composite photoanode was constructed, and the LDH two-dimensional nanometers were staggered to the nano wall structure with the vertical BiVO4 surface. The composite photoanode was used as a composite photoanode. The initial potential of the photocurrent is significantly reduced by 610 mV than that of the simple BiVO4, and the photoelectric conversion efficiency (IPCE) and the oxidation efficiency are obviously enhanced. This is first because the catalytic action of LDH enhances the surface water oxidation reaction rate, and the network formed by the two dimensional nanoscale reduces the distance of the photogenerated hole diffusion; in addition, the band gap and relative energy of BiVO4 and LDH The study provides an idea for the design of a composite photoanode with three heavy properties coupled with a catalytic / photosensitive / two-dimensional structure..3. has developed a method to regulate the morphology and size of the BiVO4 photoanode with Zn2+ as a additive. The BiVO4 photoanode with different particle size, particle pore and surface roughness is obtained. The optical current of the optimized BiVO4 increased by 3 times at 1.23 V, which is due to the higher surface roughness and smaller particle size of the controlled BiVO4, which is beneficial to the separation of the body phase charge. This work uses low price, non-toxic zinc ions as additives and controls the structure of BiVO4 at the growth stage without affecting its composition. It is a simple and effective way to control the size and morphology of the anode.

【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2;O646.54

【共引文献】