球粒状和棒状纳米赤铁矿光电化学特性研究

摘要

In this study,nanosphere and nanorod hematite were synthesized through electrode position,and both were confirmed as the pure and sole phase of hematite by XRD and Raman.Morphological observations by SEM of electrodes showed that the diameter of nanosphere hematite particles was 20 + 5 nm,and nanorod hematite particles synthesized in eletrolyte containing ethylene glycol had the length of 90 + 10 nm and the diameter of about 20 nm.They both exhibited significant absorption in the range of 300 ～ 550 nm in the UV-Vis spectroscopy,and the calculated bandgap width for nanosphere and nanorod hematite was 2.00 eV and 1.99 eV,respectively.The calculated carrier density for nanospheres was 3.16 × 1020 cm-3 and that for nanorods was 1.95× 1021 cm-3,fitted through Mott-Schottky curves measured in 1 M KOH solution.The results of photoelectrochemical experiments indicated that the current density of nanorods was lifted up to 5.5 times with illumination compared with that under dark condition under the potential of 0.6 V (vs.Ag/AgC1).Nevertheless,the fact that the current density of nanospheres rose by just about 77 ％ indicated that,although both nanosphere and nanorod hematite exhibited photoelectric response,the nanorods performed a more remarkable capacity in photoelectrocatalysis.%本文以乙二醇为诱导剂通过电化学沉积法成功合成了球粒状及棒状纳米赤铁矿.X射线衍射光谱(XRD)和Raman光谱结果表明,球粒状赤铁矿粒径20±5 nm:棒状赤铁矿截面直径约20 nm,长90±10 nm;二者物相皆为单一均匀的赤铁矿.紫外-可见吸收光谱显示两种赤铁矿在300～550nm范围内均有较好吸收,Tauc方程计算球粒状和棒状赤铁矿禁带宽度分别为2.00 eV和1.99 eV.Mott-Schottky拟合结果表明1 M KOH溶液体系中,棒状赤铁矿载流子浓度为1.95×1021 cm-3,高于球粒状赤铁矿(3.16×1020 cm-3).进一步的光电化学实验表明:0.6V(vs.Ag/AgCl)电势下棒状赤铁矿光照下电流密度较暗电流提升550％,球粒状赤铁矿电流密度提升77％.研究证实,赤铁矿形貌对其半导体特性及光电化学特性有影响,且棒状赤铁矿电极表现出更好的可见光响应特性,具有更佳的光电催化潜力.