Iron oxide nanotube film formed on carbon steel for photoelectrochemical water splitting: effect of annealing temperature

Abstract

Carbon steels (CSs) were anodized in an ethylene glycol solution containing 3 vol.% H 2 O and 0.1 M NH 4 F to coat with nanotube arrays film. The as anodized nanotube arrays film were annealed in argon atmosphere at various temperatures ranging from 250 to 550°C for 4 h. The morphology and crystal phases of the film developed after annealing processes were examined using field emission scanning electron microscopy, X-ray diffraction. Morphology transforms from nanobube arrays to nanotube bundles at 250°C, to nanobube bundles with nanoflakes at 350 and 450°C, to nanotube bundles with nanobelts at 550°C. Amorphous transformed completely into maghemite at 350°C and hematite with minor magnetite at 450 and 550°C. Diffuse reflectance ultraviolet and visible spectra revealed iron oxide nanotube film annealed at 350°C, or higher than 350°C behaved tremendous absorbance ability in visible spectra range. Mott-Schottky analysis and linear scan voltammetry were performed in 1 M NaOH to show that iron oxide nanotube film annealed at 450°C exhibited best charge carrier transfer ability upon illumination and superior photoelectrochemical properties compared with the films annealed at other temperatures. The film annealed at 450°C displayed the photocurrent density of 0.13 mA cm À2 at 0.2 V Ag/AgCl , but the film annealed at other temperatures with the photocurrent densities of lower than 0.05 mA cm À2 at 0.2 V Ag/AgCl . The morphology and phase transform of iron oxide nanotube film at different annealing temperature results in the change of their photoelectrochemical properties.

CdS-Decorated Porous Anodic SnOx Photoanodes with Enhanced Performance under Visible Light

“…Many scientific efforts are focused on designing electrode materials that fulfill the most criteria for efficient water splitting. One of them is the use of self-supported nanostructured photoanodes formed directly by anodic oxidation (anodization) of particular metals, such as titanium [ 4 , 5 ], zinc [ 6 , 7 ], tungsten [ 8 , 9 ], iron [ 10 , 11 ], or tin [ 12 , 13 , 14 ].…”

Study on the Crystallinity and Oxidation States of Nanoporous Anodized Tin Oxide Films Regulated by Annealing Treatment for Supercapacitor Application

“…On the other hand, annealing can change the composition of anodized films. Studies have shown that through different annealing treatments, a metal iron oxide layer can be obtained with a mixture of different kinds of iron oxides such as hematite and magnetite. − The important and stable oxidation states of tin are SnO 2 and SnO. The theoretical specific capacity of SnO 2 is almost 3 times that of carbon materials.…”

Estudo da formação de heterojunção e dopagem em nanotubos de TiO>sub<2>/sub<: estratégias para melhorar a eficiência na fotossíntese artificial para a geração de hidrogênio

“…A aplicação de nanotubos também é variada, podendo ser aplicada em sensor de gases, aplicações biomédicas, baterias e em células fotoeletroquimicas73,74,28 . Também o método de anodização pode ser estendido para diversos materiais com Fe2O3 e Ta2O5, sendo uma técnica muito versátil na construção de nanoestruturas75,29 . O processo de anodização consiste de um ataque eletroquímico controlado sob uma tensão anódica.…”