ChemSusChem. 2014 Mar;7(3):934-40. doi: 10.1002/cssc.201300603.
Anodization of iron substrates is one of the most simple and effective ways to fabricate nanotubular (and porous) structures that could be directly used as a photoanode for solar water splitting. Up to now, all studies in this field focused on achieving a better geometry of the hematite nanostructures for a higher efficiency. The present study, however, highlights that the purity of the iron substrate used for any anodic-hematite-formation approach is extremely important in view of the water-splitting performance. Herein, anodic self-organized oxide morphologies (nanotubular and nanoporous) are grown on different iron substrates under a range of anodization conditions, including elevated temperatures and anodization supported by ultrasonication. Substrate purity has not only a significant effect on oxide-layer growth rate and tube morphology, but also gives rise to a ninefold increase in the photoelectrochemical water-splitting performance (0.250 vs. 0.028 mA cm−2 at 1.40 V vs. reversible hydrogen electrode under AM 1.5 100 mW cm−2 illumination) for 99.99 % versus 99.5 % purity iron substrates of similar oxide geometry. Elemental analysis and model alloys show that particularly manganese impurities have a strong detrimental effect on the water-splitting performance.
铁基的阳极氧化处理是制备纳米管状（和多孔）结构的最简便、最有效的方法之一，这种结构可直接用作太阳能水分解的光阳极。到目前为止，该领域的所有研究都集中在实现更好的赤铁矿纳米结构几何形状以提高效率上。然而，本研究强调，就水分解性能而言，用于任何阳极赤铁矿形成方法的铁基底的纯度极其重要。在此，在不同的阳极氧化条件下，包括升高的温度和超声辅助的阳极氧化，在不同的铁基底上生长出了阳极自组织氧化物形态（纳米管状和纳米多孔）。基底纯度不仅对氧化层生长速率和管形态有显著影响，而且还使光电化学水分解性能提高了九倍（在 1.40 V 相对于可逆氢电极下，在 AM 1.5 100 mW/cm2 的光照下，99.99%纯度的铁基底为 0.250 mA/cm2，而 99.5%纯度的铁基底为 0.028 mA/cm2）。元素分析和模型合金表明，特别是锰杂质对水分解性能有很强的不利影响。
