Topic
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.
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TL;DR: Performing ab initio DFT+U molecular dynamics calculations of cluster models in explicit water solution, insight is provided into the pathways for oxygen evolution of a cobalt-based catalyst (CoCat) and suggests interesting similarities between the CoCat and the Mn4Ca-oxo oxygen evolving complex of photosystem II.
Abstract: The in-depth understanding of the molecular mechanisms regulating the water oxidation catalysis is of key relevance for the rationalization and the design of efficient oxygen evolution catalysts based on earth-abundant transition metals. Performing ab initio DFT+U molecular dynamics calculations of cluster models in explicit water solution, we provide insight into the pathways for oxygen evolution of a cobalt-based catalyst (CoCat). The fast motion of protons at the CoCat/water interface and the occurrence of cubane-like Co-oxo units at the catalyst boundaries are the keys to unlock the fast formation of O–O bonds. Along the resulting pathways, we identified the formation of Co(IV)-oxyl species as the driving ingredient for the activation of the catalytic mechanism, followed by their geminal coupling with O atoms coordinated by the same Co. Concurrent nucleophilic attack of water molecules coming directly from the water solution is discouraged by high activation barriers. The achieved results suggest also...
222 citations
TL;DR: Electrochemical test results indicated that the Co-free materials delivered high capacity with excellent capacity retention and reasonable rate capability, and the cation mixing in Li(Ni0.9Mn0.1)O2 increased slightly even after the extensive cycling at the elevated temperature, ascribed to the structural integrity induced from the optimized synthetic condition using the coprecipitation.
Abstract: We propose a feasibility of Co-free Ni-rich Li(Ni1–xMnx)O2 layer compound. Li(Ni1–xMnx)O2 (0.1 ≤ x ≤ 0.5) have been synthesized by a coprecipitation method. Rietveld refinement of X-ray diffraction and microscopic studies reveal dense and spherical secondary particles of highly crystalline phase with low cation mixing over the whole compositions, implying successful optimization of synthetic conditions. Electrochemical test results indicated that the Co-free materials delivered high capacity with excellent capacity retention and reasonable rate capability. In particular, Li(Ni0.9Mn0.1)O2, which possesses the lowest cation mixing in the Li layers among samples, exhibited exceptionally high rate capacity (approximately 149 mAh g–1 at 10 C rate) at 25 °C and high discharge capacity upon cycling under a severe condition, in the voltage range of 2.7–4.5 V at 55 °C. The cation mixing in Li(Ni0.9Mn0.1)O2 increased slightly even after the extensive cycling at the elevated temperature, which is ascribed to the str...
222 citations
TL;DR: In this article, it was shown that a combined investigation of the magnetic and the semiconducting properties of the solid solutions of LaMnO3 and LaCoO3 is necessary for a complete understanding of this rather complicated system.
Abstract: In this paper it is shown that a combined investigation of the magnetic and the semiconducting properties of the solid solutions of LaMnO3 and LaCoO3 is necessary for a complete understanding of this rather complicated system. The conductivity gives information on the valency states of the ions and with this knowledge the magnetic properties become understandable. Mixtures of Mn3+ and Co3+ ions tend to the formation of Mn4+–Co2+ pairs having a positive magnetic superexchange interaction.
222 citations
TL;DR: In this article, the adsorption properties of manganese-promoted Co/TiO2 Fischer-Tropsch (FT) catalysts were investigated by diffuse reflectance infrared spectroscopy (DRIFTS) using CO and H2 as probe molecules.
222 citations
TL;DR: In this article, an enriched graphitic N-doped carbon-supported Fe3O4 nanoparticles composite was prepared via a solvothermal carbonization process, which exhibits a similar high catalytic activity with the 4e− reaction pathway but superior stability to Pt/C for the ORR in alkaline media.
Abstract: Graphitic N is proposed to be one of the most likely active sites for the oxygen reduction reaction (ORR) in N-doped carbon materials. However, the recent hybrid composites consisting of N-doped carbons and transition metal oxides for the ORR are predominantly pyridinic N- and pyrrolic N-doped carbon-supported cobalt or manganese oxides. Here, an enriched graphitic N-doped carbon-supported Fe3O4 nanoparticles composite was prepared via a solvothermal carbonization process. The hybrid composite exhibits a similar high catalytic activity with the 4e− reaction pathway but superior stability to Pt/C for the ORR in alkaline media. Furthermore, the composite also shows a better ORR performance than previously reported transition metal oxides-based N-doped carbon hybrid composites. The unusual high catalytic activity arises from the combination of the high surface area and the synergetic coupling effect between the enriched graphitic N-doped carbon and Fe3O4 nanoparticles.
222 citations