Abstract
Mixed transition-metals oxide electrocatalysts have shown huge potential for electrochemical water oxidation due to their earth abundance, low cost and excellent electrocatalytic activity. Here we present Co–Fe–B–O coatings as oxygen evolution catalyst synthesized by Pulsed Laser Deposition (PLD) which provided flexibility to investigate the effect of morphology and structural transformation on the catalytic activity. As an unusual behaviour, nanomorphology of 3D-urchin-like particles assembled with crystallized CoFe2O4 nanowires, acquiring high surface area, displayed inferior performance as compared to core–shell particles with partially crystalline shell containing boron. The best electrochemical activity towards water oxidation in alkaline medium with an overpotential of 315 mV at 10 mA/cm2 along with a Tafel slope of 31.5 mV/dec was recorded with core–shell particle morphology. Systematic comparison with control samples highlighted the role of all the elements, with Co being the active element, boron prevents the complete oxidation of Co to form Co3+ active species (CoOOH), while Fe assists in reducing Co3+ to Co2+ so that these species are regenerated in the successive cycles. Thorough observation of results also indicates that the activity of the active sites play a dominating role in determining the performance of the electrocatalyst over the number of adsorption sites. The synthesized Co–Fe–B–O coatings displayed good stability and recyclability thereby showcasing potential for industrial applications.Graphic
Highlights
The rapid industrialization coupled with large increase of population forces us to think seriously and urgently about the problem of energy and related sources of the planet
In order to explore the viability on industrial scale, Co–Fe–B–O catalyst coating was deposited by Pulsed Laser Deposition (PLD) on Fluorine Tin Oxide (FTO) electrodes
In view of studying the influence of morphology and crystallinity of Co–Fe–B–O catalyst on Oxygen Evolution Reaction (OER) performance, the mixed metal oxide coatings were annealed at three different temperatures (200 °C, 400 °C and 600 °C) in air
Summary
The rapid industrialization coupled with large increase of population forces us to think seriously and urgently about the problem of energy and related sources of the planet. Iridium oxide (IrO2) and ruthenium oxide (RuO2) catalysts are reported to be some of the best OER electrocatalysts, owing to their performance and stability in PEM electrolyzers [9] They belong to the rare inert group of catalysts and are scarcely available on earth [10]. On the other hand, Co3O4 and Co oxide nanostructures have exhibited efficient activity as Oxygen Evolution Catalysts (OECs) in electrochemical water splitting [10, 25, 26]. 3D hierarchical nanostructured coatings of Co3O4 and iron oxides synthesized with boron by using boric acid as a source of boron in the initial target mixture, displayed excellent photocatalytic [38, 39] performance. Boron was introduced in synthesis of mixed metal oxide/boride electrocatalysts towards OER displaying enhanced electrochemical performance [41, 42]. The mechanistic role of all the elements in the coating was studied in detail and discussed
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