Kawde Anurag, Annamalai Alagappan, Sellstedt Anita, Uhlig Jens, Wågberg Thomas, Glatzel Pieter, Messinger Johannes
Umeå University, Faculty of Science and Technology, Department of Chemistry, Sweden.
Phys Chem Chem Phys. 2020 Dec 23;22(48):28459-28467. doi: 10.1039/d0cp04280c.
Worldwide significant efforts are ongoing to develop devices that store solar energy as fuels. In one such approach, solar energy is absorbed by semiconductors and utilized directly by catalysts at their surfaces to split water into H2 and O2. To protect the semiconductors in these photo-electrochemical cells (PEC) from corrosion, frequently thin TiO2 interlayers are applied. Employing a well-performing photoanode comprised of 1-D n-Si microwires (MWs) covered with a mesoporous (mp) TiO2 interlayer fabricated by solution processing and functionalized with α-Fe2O3 nanorods, we studied here the function of this TiO2 interlayer by high-energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) spectroscopy, along with X-ray emission spectroscopy (XES) and standard characterization techniques. Our data reveal that the TiO2 interlayer not only protects the n-Si MW surface from corrosion, but that it also acts as a template for the hydrothermal growth of α-Fe2O3 nanorods and improves the photocatalytic efficiency. We show that the latter effect correlates with the presence of stable oxygen vacancies at the interface between mp-TiO2 and α-Fe2O3, which act as electron traps and thereby substantially reduce the charge recombination rate at the hematite surface.
全球正在进行重大努力来开发将太阳能存储为燃料的装置。在一种这样的方法中，太阳能被半导体吸收，并在其表面由催化剂直接利用以将水分解为H2和O2。为了保护这些光电化学电池（PEC）中的半导体免受腐蚀，通常会应用薄的TiO2中间层。在此，我们使用由一维n型硅微线（MW）组成的性能良好的光阳极，该微线覆盖有通过溶液处理制备并用α-Fe2O3纳米棒功能化的介孔（mp）TiO2中间层，通过高能分辨率荧光检测X射线吸收近边结构（HERFD-XANES）光谱以及X射线发射光谱（XES）和标准表征技术研究了该TiO2中间层的功能。我们的数据表明，TiO2中间层不仅保护n型硅MW表面免受腐蚀，而且还充当α-Fe2O3纳米棒水热生长的模板并提高光催化效率。我们表明，后一种效应与mp-TiO2和α-Fe2O3之间界面处稳定的氧空位的存在相关，这些氧空位充当电子陷阱，从而大大降低了赤铁矿表面的电荷复合率。
