Influence of electrolyte temperature on the synthesis of iron oxide nanostructures by electrochemical anodization for water splitting

Abstract

Iron oxide nanostructures are an attractive option for being used as photocatalyst in photoelectrochemical applications such as water splitting for hydrogen production. Nanostructures can be obtained by different techniques, and electrochemical anodization is one of the simplest methods which allows high control of the obtained morphology by controlling its different operational parameters. In the present study, the influence of the electrolyte temperature during electrochemical anodization under stagnant and hydrodynamic conditions was evaluated. Temperature considerably affected the morphology of the obtained nanostructures and their photoelectrochemical behavior. Several techniques were used in order to characterize the obtained nanostructures, such as Field Emission Scanning Electron Microscopy (before and after the annealing treatment in order to evaluate the changes in morphology), Raman spectroscopy, photocurrent vs. potential measurements and Mott-Schottky analysis. Results revealed that the nanostructures synthesized at an electrolyte temperature of 25 ⁰C and 1000 rpm are the most suitable for being used as photocatalysts for water splitting.

The Use of Anodic Oxides in Practical and Sustainable Devices for Energy Conversion and Storage

“…Regarding PEC systems, the anodization of iron substrates was performed in EG + water + fluoride ions via potentiostatic (50 V, 15 min) [ 77 ] or pulsed [ 22 ] methods. Fe 2 O 3 film annealing was carried out at 500 °C for 1 h in an Ar atmosphere to form the hematite phase [ 77 ].…”

“…The recent papers describing the water-splitting devices using anodic oxides mainly explored photoanodes based on TiO 2 -NT [ 10 , 19 , 54 , 82 , 102 , 103 , 104 ], WO x [ 20 , 21 , 51 , 69 , 70 , 71 , 101 ], Fe 2 O 3 [ 22 , 77 ], and ZnO [ 73 , 74 ]. These studies focus on improving the photocurrent density and overall PEC efficiency by developing electrodes with specific bandgap properties, crystallinity, and morphology.…”

“…With a suitable bandgap to absorb visible-light irradiation, the use of hematite (Fe 2 O 3 ) obtained via iron anodization was also explored for water splitting applications despite its low conductivity [ 22 , 77 ]. To improve PEC water-splitting performance, Lv et al [ 22 ] doped hematite by adding Sn 2+ ions in the electrolyte during the synthesis to enhance the oxide film’s conductivity.…”

Fabrication of Ordered and High-Performance Nanostructured Photoelectrocatalysts by Electrochemical Anodization: Influence of Hydrodynamic Conditions

“…Electrochemical anodization was carried out at room temperature with an ethylene glycol-based solution with 0.1 M NH 4 F and 3% vol. H 2 O for 15 min at 50 V with iron rod as working electrode and a platinum foil as counter electrode [63]. Different rotation speeds: 0, 1000, 2000 and 3000 rpm, corresponding to Reynolds numbers of 0, 165, 325 and 490, respectively, were applied.…”

Highly Self-Organized Materials: Formation Mechanism and Electrochemical Synthesis

“…Several researches have been undertaken and different methods were used for the fabrication of organized nanostructures: lithography techniques [11,12], ion sputtering [13,14], bottom-up approach [15], i.e. building up nanostructures, electrochemical methods [16,17], template synthesis [18,19] etc. Although some of these methods are successfully used and have given impressive results in the reproduction of self organized nano-architectures, most of the nanophenomena that rule on their formation are totally or partially unknown.…”