Cobalt

About: Cobalt is a research topic. Over the lifetime, 69899 publications have been published within this topic receiving 1242058 citations. The topic is also known as: Co & Element 27.

Alkaline free electroless deposition

Abstract: Alkali-free layers of pure metals such as copper, nickel and cobalt were deposited on noble metal or noble metal sensitized substrates by electroless deposition using pure quaternary ammonium hydroxides or quaternary phosphonium hydroxides to generate the hydroxyl ion (OH - ) needed to produce electrons for the metal reduction. Using the new alkaline-free electroless compositions, uniform, continuous and reproducible metal layers were selectively deposited with excellent electrical properties. With the improved compositions and process, nanosize copper lines having widths in the range of 100 to 500 nm were prepared.

Methane combustion on some perovskite-like mixed oxides

Abstract: Some perovskite-like mixed oxides of general formula La1−xA′xBO3 were prepared by the amorphous citrate method and tested for methane combustion within the 300–600°C temperature range. Substitution at A-site with a bivalent (Eu, Sr) or tetravalent (Ce) metal cation led to a decrease or increase of catalytic activity, respectively. La0.9Ce0.1CoO3 proved to be the most active catalyst, showing complete conversion at 500°C. The nature of the metal cation introduced modifies the oxidation state of cobalt, which leads to the formation of cationic or anionic vacancies. TPD-MS analysis confirmed that the catalytic activity is related to the oxygen storage properties of the catalyst. The substitution at B-site (B=Fe, Co, Ni) allowed to find interesting correlations between catalytic activity and the temperature Tmax of maximum oxygen desorption rate.

Fenton-like degradation of azo-dye Orange II catalyzed by transition metals on carbon aerogels

Abstract: This works deals with the non-biodegradable azo-dye Orange II degradation using the heterogeneous Fenton-like reaction. Two catalyst series based on transition metals (Fe, Co, Ni) were prepared trying to improve not only the catalytic performance but also to diminish the metal leaching. Thus, metal-doped carbon aerogels and supported catalysts, the latter prepared by classical wet impregnation, were tested. The catalysts were characterized by different techniques: N2 adsorption, mercury porosimetry, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Chemical oxidation of the azo-dye Orange II was carried out in a batch reactor, at atmospheric pressure and 30 °C. The influence of the preparation method, the porous characteristics of supports and metal dispersions on the metal leaching and catalytic performance were analyzed. Impregnated catalysts are in general more active than metal-doped carbon aerogels, because metal particles are more accessible to reactants, while the doped-carbon aerogels present a smaller leaching tendency. The behaviour of impregnated catalysts is determined not only by the metal used but also by the porous texture of the supports. Thus, microporosity strongly favours the Orange II adsorption capacity and tends to reduce the metal leaching, while mesoporosity strongly increases the metal dispersion and consequently, the catalytic performance. Iron is seemingly the most active metal tested, exhibiting simultaneously the lower leaching levels for all of the supports. Although cobalt is an interesting alternative in terms of activity, it exhibits unacceptable leaching degrees.

A cobalt(II) quaterpyridine complex as a visible light-driven catalyst for both water oxidation and reduction

Abstract: The complex [CoII(qpy)(OH2)2]2+ (qpy = 2,2′:6′,2′′:6′′,2′′′-quaterpyridine) is an efficient visible light-driven catalyst for both water oxidation and reduction. It catalyses photochemical oxygen evolution from water at pH 8.0 with [RuII(bpy)3]2+/S2O82− (λ = 457 nm, max TON = 335, bpy = 2,2′-bipyridine). It also catalyses photochemical hydrogen generation from [IrIII(dF(CF3)ppy)2(dtbbpy)]+/TEOA (dF(CF3)ppy = anion of 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine, dtbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine, TEOA = triethanolamine) in aqueous acetonitrile (λ > 420 nm, max TON = 1730).

Differentiating homogeneous and heterogeneous water oxidation catalysis: confirmation that [Co4(H2O)2(α-PW9O34)2]10- is a molecular water oxidation catalyst.

Abstract: Distinguishing between homogeneous and heterogeneous catalysis is not straightforward. In the case of the water oxidation catalyst (WOC) [Co4(H2O)2(PW9O34)2]10– (Co4POM), initial reports of an efficient, molecular catalyst have been challenged by studies suggesting that formation of cobalt oxide (CoOx) or other byproducts are responsible for the catalytic activity. Thus, we describe a series of experiments for thorough examination of active species under catalytic conditions and apply them to Co4POM. These provide strong evidence that under the conditions initially reported for water oxidation using Co4POM (Yin et al. Science, 2010, 328, 342), this POM anion functions as a molecular catalyst, not a precursor for CoOx. Specifically, we quantify the amount of Co2+(aq) released from Co4POM by two methods (cathodic adsorptive stripping voltammetry and inductively coupled plasma mass spectrometry) and show that this amount of cobalt, whatever speciation state it may exist in, cannot account for the observed wa...