FeO-Based Hierarchical Structures on FTO Substrates and Their Photocurrent

Weiwei Xia; Jiawei Sun; Xianghua Zeng; Pengdi Wang; Min Luo; Jing Dong; Huaguang Yu

doi:10.1021/acsomega.9b03197

FeO-Based Hierarchical Structures on FTO Substrates and Their Photocurrent

ACS Omega. 2020 Feb 3;5(5):2205-2213. doi: 10.1021/acsomega.9b03197. eCollection 2020 Feb 11.

Authors

Weiwei Xia¹, Jiawei Sun¹, Xianghua Zeng^{1

2}, Pengdi Wang¹, Min Luo¹, Jing Dong^{1

3}, Huaguang Yu¹

Affiliations

¹ College of Physics Science and Technology & Institute of Optoelectronic Technology, Yangzhou University, Yangzhou 225002, P. R. China.
² College of Electrical, Energy and Power Engineering, Yangzhou University, Yangzhou 225127, P. R. China.
³ College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, P. R. China.

Abstract

As one of the most promising photoanode materials for photoelectrochemical (PEC) water oxidation, earth-abundant hematite has been severely restricted by its poor electrical conductivity, poor charge separation, and sluggish oxygen evolution reaction kinetics. FeO has an ability to produce hydrogen, while its preparation needs high temperature to reduce Fe³⁺ to Fe²⁺ by using H₂ or CO gases. Here, Fe₂O₃- and FeO-based nanorods (NRs) on fluorine-doped tin oxide (FTO) substrate have been prepared, where the latter was obtained by doping Sn⁴⁺ ions in FeOOH to reduce Fe³⁺ ions to Fe²⁺. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements indicate that the dominant content of Fe element on the surface of Sn-doped Fe₂O₃ and Sn-FeOOH samples is Fe²⁺. FeO-based NRs have a Fe₃O₂/FeO heterostructure with some SnO₂ nanoparticles distributed on their surface. These prepared samples were used as PEC photoanodes under a visible-light irradiation. The results showed that the modified FeO-based NRs have a photocurrent density of 0.2 mA cm^-2 at 1.23 V vs reference hydrogen electrode (RHE) using Hg/HgO electrode as the reference electrode. Furthermore, they also have a better photocatalytic hydrogen evolution activity with a rate of 2.3 μmol h^-1 cm^-1. The improved photocurrent and photocatalytic activity can be ascribed to the Sn-dopant, as the introduction of Sn⁴⁺ not only leads to the formation of the Fe₃O₂/FeO heterostructure but also increases the carrier concentration. Fe₃O₂/FeO heterostructure with SnO₂ nanoparticles on its surface has a good band energy alignment, which is beneficial to the PEC water oxidation and reduction.