基于三维多孔透明Sb:SnO2纳米电极/Fe2O3/助催化剂构型的新型光阳极的制备及光电化学性能研究

Construction of high efficient semiconductor photoanode with visible light response is a key issue in research on photoelectrochemical water splitting. Starting from the structural design, this project intends to construct high performance photoelectrochemical photoanode for water oxidation by using three dimensional porous transparent conductive Sb:SnO2 nano-electrode as substrate, followed by depositing visible light responsive materials of Fe2O3 which will be treated by laser annealing for improving the crystallization and surface modification of cocatalyst for improving the surface reaction rate. The three-dimensional porous structure and transparency could facilitate to improve the loading amount of Fe2O3 and the utilization of sun light; the conductive nano-networks and surface cocatalysts could improve the export capability of photogenerated electrons and the surface water oxidation abilities of photogenerated holes. In this project, the microstructures, surface areas, conductivities of three-dimensional porous electrodes, and the surface morphology, crystallization, surface chemical state of the deposited Fe2O3 would be investigated by adjusting various material preparation conditions to obtain photoelectrochemical photoanode with three dimensional porous structures for high efficient water oxidations; the generation, separation, transportation, surface reaction of photogenerated electrons and holes in the three-dimensional porous Fe2O3 photoanode and the factors that influence the above kinetics process would be studied, to explore the new idea of designing high performance Fe2O3 photoanodes. The researches of this subject are expected to open new routes and give experimental foundations in designing photoelectrodes for high efficient water splitting, photoelectrocatalysis, and solar cells.

高效可见光响应半导体光阳极的构建是光电化学水分解研究的核心问题。本项目拟从结构设计入手，以三维多孔透明导电Sb:SnO2纳米电极为基底，沉积Fe2O3可见光响应材料，通过激光退火改善其结晶性，通过表面复合助催化剂改善表面反应速率，构建高性能光电化学水分解光阳极。利用三维多孔结构及其透明性提高Fe2O3负载量和太阳光利用率；利用纳米导电网络和表面助催化剂提高光生电子的导出能力和光生空穴的表面氧化水能力。研究材料制备的各种过程因素对三维多孔电极的微观结构、表面积、导电能力，以及Fe2O3的表面形貌、结晶性、表面化学状态的影响规律，获得高效氧化水性能的三维多孔Fe2O3光阳极；研究三维多孔Fe2O3光阳极中光生电子空穴的产生、分离、输运、表面反应等动力学过程的影响因素，探索高性能Fe2O3光阳极设计的新思路。本项目的实施将为高效水分解、光电催化以及太阳能电池电极设计提供新的途径和奠定实验基础。

重要结果、关键数据：.1. 利用PS微球模板制备了多孔结构Sb:SnO2导电衬底，水热方法生长了珊瑚状的Fe2O3纳米线。三维多孔导电衬底减小了Fe2O3光生空穴的扩散距离，增加了Fe2O3和电解液的接触面积，提高光子吸收利用率，增加氧化铁的负载量。同时改善了光阳极表面的亲水特性。高温快速退火处理，不仅提高Fe2O3的结晶性，同时减小了氧化铁的电荷传输电阻。1.23 V vs. RHE电位下，光电流密度为1.32 mA.cm-2。结合TiCl4处理，形成一层薄薄的氧化钛钝化层，同样电位下，光电流提高到1.8 mA.cm-2。.2. 高温快速退火使TiO2阻挡层中的Ti4+热扩散进入到Fe2O3晶格中。提高了Fe2O3光阳极体内电荷传输能力、表面电荷分离能力，同时提高了Fe2O3薄膜的结晶性，减少表面态引起的复合，显著提高Fe2O3光阳极的光电化学性能，光电流达到0.75 mA.cm-2。.3.高温快速退火激活了Fe2O3中掺杂的Ti，更多的Ti原子掺到Fe2O3中，载流子浓度显著提高，最大值1.31×1019cm-3是5%-Ti:Fe2O3-500的19.4倍。薄膜的结晶性明显改善，表面粗糙度增加。高温快退使样品的电荷转移电阻减小，1.23Vvs.RHE 电位下，光电流密度提高到0.92 mA.cm-2。.4. H-BiVO4电极连续测试3小时后增强效果消失，而无定型TiO2保护的光阳极经8小时的稳定性测试表明：每个循环的峰值电流强度都一致。无定型TiO2保护层阻止氧空位与氧分子接触，防止氧空位被愈合，不妨碍电子的转移，提高氢处理光阳极的PEC稳定性，同时维持良好的氧化性能。.我们相信三维多孔导电结构结合高温快速退火方法对光阳极性能的改善可应用到其它光电器件及光阳极。