Energy Materials Lab (EML), School of Sciences and Engineering, The American University in Cairo , New Cairo 11835, Egypt.
ACS Nano. 2014 May 27;8(5):4915-23. doi: 10.1021/nn5009066. Epub 2014 Apr 16.
Vertically oriented Ta-W-O nanotube array films were fabricated via the anodization of Ta-W alloy foils in HF-containing electrolytes. HF concentration is a key parameter in achieving well-adhered nanotube array structure. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements confirm the staggered band-alignment between Ta2O5 and WO3, which facilitates the separation of charge carriers. The nanotubes made of Ta-W films containing 10% W showed 100-fold improvement in the measured photocurrent compared to pristine Ta2O5 upon their use to split water photoelectrochemically. This enhancement was related to the efficient charge transport and the red shift in absorption spectrum with increase of the W content, which was asserted by ultrafast transient absorption (TA) spectroscopy measurements. The TA measurements showed the elimination of trap states upon annealing Ta-W-O nanotubes and, hence, minimizing the charge carrier trapping, whereas the trap states remain in pristine Ta2O5 nanotubes even after annealing.
垂直取向的 Ta-W-O 纳米管阵列薄膜是通过在含 HF 的电解液中对 Ta-W 合金箔进行阳极氧化制备的。HF 浓度是获得附着力良好的纳米管阵列结构的关键参数。X 射线光电子能谱（XPS）和漫反射测量证实了 Ta2O5 和 WO3 之间的能带交错排列，这有利于载流子的分离。在用于光电化学分解水时，与原始的 Ta2O5 相比，含有 10%W 的 Ta-W 薄膜制成的纳米管的测量光电流提高了 100 倍。这种增强与有效的电荷输运以及吸收光谱随 W 含量增加的红移有关，这是通过超快瞬态吸收（TA）光谱测量得到的。TA 测量表明，退火 Ta-W-O 纳米管消除了陷光态，从而最大限度地减少了载流子俘获，而在退火后，原始 Ta2O5 纳米管中仍存在陷光态。
