氢氟酸腐蚀对α-Fe2O3薄膜光解水电极光电化学性质的影响

使用溶胶-凝胶法制备了α-Fe₂O₃薄膜,研究了氢氟酸腐蚀薄膜表面对其光电化学性质的影响. 实验发现,薄膜表面的孔洞和间隙随着氢氟酸浸蚀时间的增长而发生变化. 氢氟酸浸蚀5 min,α-Fe₂O₃电极的光电流降低;随后随浸蚀时间增加而迅速增加;当浸蚀时间大于15 min时,其光电流再次下降,但对浸蚀过的样品再次退火可以使光电流大幅增加. 通过电化学交流阻抗谱、拉曼和X射线光电子能谱分析,提出了两个影响光电流的因素：氢氟酸表面浸蚀造成薄膜表面的多孔性和结晶度降低. 为此,通过示意图解释了结合浸蚀和退火后处理两个步骤来增强α-Fe₂O₃薄膜光解水电极光电活性的原理. 相对于初始的α-Fe₂O₃电极,浸蚀并且再退火处理后,其光电性质更加稳定.

Effect of HF Treatment on the Photoelectrochemical Properties of a Hematite Thin Film Photoanode for Water Splitting

The effects of HF treatment on the photoelectrochemical (PEC) properties of sol-gel prepared hematite (α-Fe₂O₃) thin films were investigated. Pores and interstices between the grains developed on the film surface as the HF etching time increased. The photocurrent density of the α-Fe₂O₃ photoanode decreased within the first 5 min of etching, and then increased quickly as the etching time increased. At longer time than 15 min the photocurrent density deteriorated. Re-annealing the etched samples significantly enhanced the photocurrent density. Based on electrochemical impedance spectroscopy, Raman and X-ray photoelectron spectroscopies, we propose that two factors contribute to photocurrent density reversely: the porosity and the lowered crystallinity of the α-Fe₂O₃ surface because of HF treatment.Aschematic model was compiled to explain the enhanced PEC activities of the etched plus re-annealed α-Fe₂O₃ photoanode. The PEC and water splitting measurements showed that the etched plus re-annealed photoanode is more stable than the as-prepared one.