KLGHEI of Environment and Energy Chemistry, MOE of the Key Laboratory of Bioinorganic and Synthetic Chemistry, MOE of the Key Laboratory of Bioinorganic and Synthetic Chemistry, The Key Lab of Low-carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry, Sun Yat-Sen University , Guangzhou 510275, People's Republic of China.
Department of Chemistry and Biochemistry, University of California , Santa Cruz, California 95064, United States.
Nano Lett. 2017 Apr 12;17(4):2490-2495. doi: 10.1021/acs.nanolett.7b00184. Epub 2017 Mar 27.
High-temperature activation has been commonly used to boost the photoelectrochemical (PEC) performance of hematite nanowires for water oxidation, by inducing Sn diffusion from fluorine-doped tin oxide (FTO) substrate into hematite. Yet, hematite nanowires thermally annealed at high temperature suffer from two major drawbacks that negatively affect their performance. First, the structural deformation reduces light absorption capability of nanowire. Second, this "passive" doping method leads to nonuniform distribution of Sn dopant in nanowire and limits the Sn doping concentration. Both factors impair the electrochemical properties of hematite nanowire. Here we demonstrate a silica encapsulation method that is able to simultaneously retain the hematite nanowire morphology even after high-temperature calcination at 800 °C and improve the concentration and uniformity of dopant distribution along the nanowire growth axis. The capability of retaining nanowire morphology allows tuning the nanowire length for optimal light absorption. Uniform distribution of Sn doping enhances the donor density and charge transport of hematite nanowire. The morphology and doping engineered hematite nanowire photoanode decorated with a cobalt oxide-based oxygen evolution reaction (OER) catalyst achieves an outstanding photocurrent density of 2.2 mA cm at 0.23 V vs Ag/AgCl. This work provides important insights on how the morphology and doping uniformity of hematite photoanodes affect their PEC performance.
高温激活通常用于通过诱导氟掺杂氧化锡（FTO）衬底中的 Sn 扩散进入赤铁矿来提高用于水氧化的赤铁矿纳米线的光电化学（PEC）性能。然而，高温退火的赤铁矿纳米线存在两个主要缺点，这会对其性能产生负面影响。首先，结构变形降低了纳米线的光吸收能力。其次，这种“被动”掺杂方法导致 Sn 掺杂剂在纳米线中分布不均匀，并限制了 Sn 的掺杂浓度。这两个因素都损害了赤铁矿纳米线的电化学性能。在这里，我们展示了一种二氧化硅封装方法，即使在 800°C 的高温煅烧后，它仍能够同时保留赤铁矿纳米线的形态，并改善掺杂剂在纳米线生长轴上的浓度和均匀性分布。保留纳米线形态的能力允许调整纳米线长度以实现最佳的光吸收。Sn 掺杂的均匀分布增强了赤铁矿纳米线的施主密度和电荷输运。用基于钴氧化物的析氧反应（OER）催化剂修饰的形态和掺杂工程化的赤铁矿纳米线光阳极实现了在 0.23 V vs Ag/AgCl 时 2.2 mA cm 的出色光电流密度。这项工作提供了关于赤铁矿光阳极的形态和掺杂均匀性如何影响其 PEC 性能的重要见解。
