Green Synthesis of Iron-Doped Cobalt Oxide Nanoparticles from Palm Kernel Oil via Co-Precipitation and Structural Characterization.

Cedrik Ngnintedem Yonti,Patrice Kenfack Tsobnang,Roussin Lontio Fomekong,Arnaud Delcorte,Yvan Larondelle,Francois Devred,Sophie Hermans,John Lambi Ngolui,Eric Mignolet

doi:10.3390/nano11112833

Abstract

In this study, a bio-derived precipitating agent/ligand, palm kernel oil, has been used as an alternative route for the green synthesis of nanoparticles of Fe-doped Co3O4 via the co-precipitation reaction. The palm oil was extracted from dried palm kernel seeds by crushing, squeezing and filtration. The reaction of the palm kernel oil with potassium hydroxide, under reflux, yielded a solution containing a mixture of potassium carboxylate and excess hydroxide ions, irrespective of the length of saponification. The as-obtained solution reacts with an aqueous solution containing iron and cobalt ions to yield the desired metallo-organic precursor, iron cobalt carboxylate. Characterization of the precursors by IR and gas chromatography (GC) attests to the presence of carboxylate fatty acids in good agreement with the proportion contained in the oil, and ICP confirms that the metallic ratios are in the proportion used during the synthesis. Analysis of the products thermally decomposed between 400 °C and 600 °C by XRD, EDX, TEM and ToF-SIMS, established that cobalt iron oxide nanoparticles (Co(1−x)Fex)3O4 were obtained for x ≤ 0.2 and a nanocomposite material (Co(1−x)Fex)3O4/Fe3O4 for x ≥ 0.2, with sizes between 22 and 9 nm. ToF-SIMS and XRD provided direct evidence of the progressive substitution of cobalt by iron in the Co3O4 crystal structure for x ≤ 0.2.

Highlights

In the last three decades, much research has been devoted to the synthesis and characterization of materials at the nano scale
We report, for the first time and to the best of our knowledge, the use of a carboxylate ligand extracted from palm kernel oil, a Cameroonian local oil product, as the precipitating agent for synthesis of mixed cobalt-iron oxide, (Co(1−x) Fex )3 O4 (x ≤ 20) and nanocomposite materials, (Co(1−x) Fex )3 O4 /Fe3 O4 (x > 20) by thermally decomposing the precursor pre-synthesized via a simple co-precipitation reaction
The results reveal that the ratios of metallic ions present in the precursor correspond to the expected value which confirms that the synthetic method adopted was good

Summary

Introduction

In the last three decades, much research has been devoted to the synthesis and characterization of materials at the nano scale. Transition metal oxide nanoparticles have attracted considerable attention and cobalt oxide, in particular, exhibits specific chemical and thermal stability [3]. It is well known as a photocatalyst [4], a catalyst in N2 O decomposition [5], a highly selective CO sensor [6], a high temperature solar selective absorber [7], an electrode material for thin film supercapacitor [8], a magnetic material [9] and it is used in electrochromic devices [10], because its optical properties changes under an external electrical stimulus.

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Results

Conclusion