三氧化二铁光阳极可控制备及光伏-光电催化分解水制氢研究

Photoelectrochemical water splitting for hydrogen generation is focus on preparation of effective photoanonde with high stability. Hematite (alpha-Fe2O3) semiconductor has attracted much attention due to its excellent chemical stability in aqueous solution, abundance in the earth, nontoxicity and low cost. The efficiency reported until now is far from the theoretical prediction because of the small hole diffusion length and slow oxygen evolution reaction kinetics. In this project, ultrathin nanoflake structure of alpha-Fe2O3 film on FTO substrate will be obtained through hydrothermal synthesis. Phosphate ions are adsorbed on certain planes of the initial nuclei, and iron ions aggregated along another planes, then resulting in formation of the nanoflake structure. The distance of photogenerated electrons and holes reaching the interface is very short, which is beneficial to charge transfer. Surface doping of metal ions, such as Ag+, will accelerate surface oxygen evolution, and promote charge transfer. In addition, phosphate absorbed on surface will establish a negative electrostatic field, which promotes extraction of photoexcited holes to the electrode surface. Perovskite solar cells will be fabricated for a PV-PEC device. PV cells provide voltage needed for water splitting in place of external potential. The project is aiming to provide high efficient alpha-Fe2O3 photoanode through nanoflake morphology, ions doping and surface modification. These results present a facile method for a better photoelectrochemical performance of hematite and new photovoltaic- photoelectrochemical tandem cells for solar water splitting.

制备高效稳定的光阳极是光电催化分解水制氢研究的重要内容。a-Fe2O3电极具有价廉、稳定无毒的优点，但空穴扩散长度短、氧化反应速率慢等缺点制约了其光电催化活性。项目采用水热法制备a-Fe2O3薄膜，通过负载磷酸盐，既达到控制其形貌，又同时完成金属离子掺杂和磷酸根修饰的三重作用。磷酸盐中磷酸根离子具有定向吸附作用，控制晶核的定向生成，制备出超薄纳米片形貌的a-Fe2O3，使电子与空穴向界面传输距离变短；磷酸盐中金属离子(如银、钴离子)掺杂到a-Fe2O3表面，能够提高电极的氧化反应速率；此外，吸附在电极表面的磷酸根基团形成负静电场，可吸引空穴迁移至界面。制备钙钛矿电池，开发光伏-光电催化分解水体系，避免使用外加电能。项目以制备高效的a-Fe2O3光阳极为主线，深入研究薄膜形貌、表面掺杂与修饰对电极的电荷分离、传输以及光电催化性能的影响，为制备高效的光阳电极和新型光伏-光电催化体系提供新方法。

α-氧化铁以禁带宽度小(约为2.2eV)，储存资源丰富，无毒、环境污染小，稳定性卓越等优势成为目前最有潜力的光催化剂之一。然而，ɑ-Fe2O3存在诸多缺点，严重限制了其光解水制氢的效率。针对α-Fe2O3光生电子与空穴在体相内容易复合的问题，通过磷酸盐对α-Fe2O3表面修饰以及形貌调控，制备超薄纳米片形貌的α-Fe2O3，将电子、空穴向界面传输的距离充分缩短，减少电子与空穴的复合机会。另一方面，针对-Fe2O3放氧反应速率慢、过电势较高的问题，分别采用Ag、Sn、Ti、Mn、Co等金属离子进行掺杂，显著增强了α-Fe2O3光阳极的催化活性，提高其氧化分解水的反应速率。针对纯α-Fe2O3 表面态较多，表面电子空穴复合严重的问题，我们采用低温化学气相沉积法，使小分子盐酸多巴胺(DA)分解产生N掺杂的碳膜均匀沉积在α-Fe2O3表面，从而有效钝化氧化铁的表面态缺陷，抑制电子空穴复合，提高光电催化氧化水的性能。最后，为制备光驱动的光伏-光电催化分解水体系，项目开展了新型钙钛矿光伏电池研究，实现太阳能-氢能的高效转换。我们设计合成一些新颖的有机空穴传输材料，作为空穴传输层应用于钙钛矿电池中。引入碳碳双键的三苯胺空穴传输材料D101，制备的n-i-p型钙钛矿太阳能电池的光电转换效率到达18.47%，电池器件稳定运行良好，为制备高效稳定的光伏电池提供了实验基础。