EXAFS study of Sn-doped hematite nanostructured films for water splitting

Hematite photoanodes are widely studied because they could offer low-cost and sustainable photoelectrodes for oxygen evolution reaction. Doping has been demonstrated an effective way to improve the photoelectrochemical properties. In particular, normally Sn is introduced into the hematite films deposited or grown on FTO (Fluorine-doped Tin Oxide) by high-temperature diffusion of Sn from the substrate. When used as photoanode, the photocurrent increases when the Sn doping iincreases from 0 to 3 at%, and then saturates (12% behaves as the 3%). Sn-doping sligtly modify the hematite lattice.We ask for a XAS investigation at Fe and Sn K-edge to measure the Fe and Sn site in hematite nanostructured films as a function of the Sn concentration and of the annealing temperature, with the aim to correlate the Sn site with the photoelectrochemical properties.

赤铁矿光阳极（hematite photoanodes）被广泛研究，因其可提供低成本且可持续的光电极，用于析氧反应（oxygen evolution reaction, OER）。掺杂已被证实是改善其光电化学性能的有效手段。具体而言，通常通过衬底中锡（Sn）的高温扩散，将锡掺杂至沉积或生长于氟掺杂氧化锡（FTO, Fluorine-doped Tin Oxide）衬底上的赤铁矿薄膜中。当用作光阳极时，光电流随锡掺杂量从0提升至3原子百分比（at%）持续升高，随后趋于饱和（掺杂量为12%时的性能与3%时相当）。锡掺杂会对赤铁矿晶格产生轻微调控。本研究拟开展铁（Fe）和锡（Sn）的K边（K-edge）X射线吸收光谱（XAS, X-ray Absorption Spectroscopy）表征，以探究不同锡掺杂浓度及退火温度下，纳米结构赤铁矿薄膜中铁和锡的位点分布情况，最终目标是建立锡位点与光电化学性能之间的关联。