Preparation and characterization of nano cobalt oxide

Abstract

Cobalt oxide Co(3)O(4) is prepared according to several methods i.e. oxalate decomposition (CoAO), surfactant-assisted precipitation (CoCTAB), sol-gel technique (CoSG) and polymer combustion (CoPVA). The solids are characterized by XRD, FTIR, TPR and TEM analysis. The method via oxalate decomposition (CoAO) appears as that giving the smallest particles nanostructured with an almost monomodal distribution, whereas the CoPVA needs to be calcined at the highest temperature in order to have pure Co(3)O(4). As a consequence on CoPVA the largest particle size is found. The reducibility by H(2) of cobalt oxide particles having the smallest (CoAO) and the largest particle size (CoPVA) is found to depend on the particle dimensions and, where the distribution is monomodal, the reduction steps Co(3)O(4) -> CoO -> Co appear clearly distinct and the temperatures relative to the two reduction steps are well beyond those monitored on microprepared oxide, where only a gross and unique reduction peak is envisaged

Synthesis of Cobalt-Based Nanomaterials from Organic Precursors

“…TEM images further validated that the porous architectures-agglomerations-are constructed from the interconnection among the primary crystalline nanoparticles with size of a few nanometers. Furthermore, the regular diffraction spots displayed from SAED pattern, validated the cubic face-centered structure of Co 3 O 4 [2,4,18,25]. HRTEM analysis also indicated the single crystalline nature of Co 3 O 4 [18,25].…”

“…Most nanoparticles had faceted morphology and high crystalline quality as verified by Selected-Area Electron Diffraction (SAED) analysis and High-Resolution Transmission Electron Microscopy (HRTEM) [26]. Pseudo-hexagonal [15,17,18,21], circular and occasionally rectangular [2] or uniform spherical [12] shaped nanoparticles were observed. In general, powders are homogeneously dispersed with dimensions ranging from 50 to 600 nm, in accordance with SEM results, mentioned above.…”

“…The "carboxylate" term includes several organic species that contain at least one carboxyl group, such as oxalate, citrate, etc. Methods for synthesis of cobalt-carboxylates include (i) sol-gel [2,4], (ii) intimate mixing of cobalt ions [6][7][8], (iii) precipitation [9,10], (iv) hot oxidation-redox reaction [11], (v) ball milling [12] and (vi) microemulsion [13]. Reaction of cobalt acetate with a carboxylic acid, for example, leads directly to the synthesis of cobalt-carboxylate, when the carboxylic acid in question is stronger than acetic acid: Co(Ac) 2 + RCOOH → Co(RCOO) 2 + 2 AcH (1).…”

“…Thermal decomposition of the dried gel in air at 400-600°C for 2 h led to Co 3 O 4 [4]. Luisetto et al have also produced Co 3 O 4 by thermal treatment of cobalt oxalate precipitate at 450°C for 2 h in air [2]. de Rivas et al prepared Co 3 O 4 nanoparticles via calcination of oxalate nanorods at 500°C in static air [15].…”

“…Transition metal-oxide nanoparticles have attracted considerable interest on account of their applications in various fields, including catalysis, electronics, coatings, gas sensing, electrochemical devices, solar energy conversion and biomedicine [2,3]. Several methods have been employed for the synthesis of cobalt nanomaterials, including: (i) microemulsion, (ii) solvothermal method, (iii) thermal decomposition of cobalt precursors, (iv) spray pyrolysis, (v) sol-gel process, etc.…”