How does anodization time affect morphological and photocatalytic properties of iron oxide nanostructures?

Abstract

Iron oxide nanostructures are promising materials to be used as photocatalysts in different photoelectrochemical applications. There are different techniques in order to synthesize these nanostructures, but one of the most inexpensive and simple method is electrochemical anodization. This method can lead to different nanostructures by controlling its parameters. Anodization time is one of the most critical parameters since it considerably affects the properties of the obtained nanostructures. In this work, different anodization times (5, 10, 15, 30 and 60 min) were studied. The resulting nanotubes were characterized by field emission scanning electron microscopy, Raman laser confocal microscopy, water splitting measurements, Mott-Schottky analysis and electrochemical impedance spectroscopy, in order to test their viability for being used as photocatalysts in photoelectrochemical applications.Results showed that the best photocurrent density values in water splitting tests (0.263 mA • cm -2 ) were achieved for the sample anodized for 10 min under hydrodynamic conditions.

Photocatalytic evaluation of CuO and ZnO crystallites synthesized hydrothermally using binary eugenol/iso-eugenol mixtures: isomer effects on the capping propensity of biogenic agents

“…The slope of the M–S plots is inversely related to the donor density of semiconductor materials. 69 It is evident from the M–S plots, as shown in Fig. 10A, that the slope progressively decreased in the case of both the CuO and ZnO series, with the lowest slopes observed for CuO-5 and ZnO-5, respectively.…”

Anodization fabrication techniques and energy-related applications for nanostructured anodic films on transition metals

“…They found that annealed nanoporous Fe 2 O 3 films exhibited a net photocurrent density of 0.51 mA cm -2 at 0.6 V vs. Ag/AgCl in an electrolyte containing 0.5 mol L -1 H 2 O 2 and 1 mol L -1 NaOH under AM 1.5 simulated solar illumination. Since then, many studies have featured the PEC properties of nanostructured iron oxide films fabricated by anodization [31][32][33][34][35][37][38][39][40][42][43][44]49,52,53,[56][57][58]67,[72][73][74][75] . The Misra group demonstrated that a photoanode with a two-layer oxide structure comprising a top layer with a nanodendrite morphology and a bottom layer with a nanoporous morphology, obtained by the two-step anodization of Fe, exhibited noticeably improved photoactivity compared to that of a single layer nanotubular oxide [33,34] .…”

“…In addition to their very promising applications in PEC water splitting, anodic iron oxide nanotube arrays have also shown good photocatalytic performance in the degradation of methylene blue under visible light [42,52] and excellent oxygen reduction reaction catalytic activity [55] . In addition, Joseph et al reported the synthesis of metal-doped iron oxide nanoporous structures achieved by an additional simple electrochemical process after Fe anodization [57,77] . The metal-doped iron oxide nanostructures exhibited enhanced photocatalytic activity.…”