Metal-organic frameworks (MOFs) are potential photocatalytic materials for CO.sub.2 reduction, however, still limited by their low efficiency. In this work, cobalt decorated UiO-66-NH.sub.2 (xCoNU, x ...presents the mass friction of cobalt) were successfully synthesized through an economic NaBH.sub.4 treating method and applied for CO.sub.2 photocatalytic reduction. It was confirmed that cobalt worked as the active site in the system, and an optimized CO yielding rate of 1.93 mmol g.sup.-1 h.sup.-1 in 3 h was achieved on 5CoNU, which is 10.2 times higher than that of UiO-66-NH.sub.2. Characterization results revealed that the highly dispersed cobalt in xCoNU accelerates the charge separation and electron transport in the photocatalytic system, improving the photocatalytic CO.sub.2 reduction performance. This work provides a simple and convenient method to modify MOFs with metal cocatalyst, and is expected to advance the development of efficient CO.sub.2 photoreduction catalysts.
In the presence of KCN, the reaction of 1,10-phenanthroline (phen) with Co (ClO.sub.4).sub.2 affords a cobalt(II) complex, (phen).sub.2Co(CN).sub.2, a co-catalyst for photochemical driven CO.sub.2 ...reduction to CO. Under visible light (lambda = 469 nm), together with Ru(phen).sub.3(PF.sub.6).sub.2 as a photosensitizer and triethanolamine (TEOA) as a sacrificial electron donor, (phen).sub.2Co(CN).sub.2 shows a high selectivity (95%) for the catalytic reduction of CO.sub.2 to CO with a turnover number (TON) of 1450 during 10 h irradiation. The photocatalytic mechanism for CO.sub.2 reduction by Co(phen).sub.2(CN).sub.2 is afforded. I hope that these findings can afford a new chemical paradigm for the design of catalysts for CO.sub.2 reduction that is highly active and selective. Graphic Co(phen).sub.2(CN).sub.2, a catalyst for visible-light-driven driven CO.sub.2 reduction to CO with a high selectivity.
A Water Soluble Cobalt Wang, Chun-Li; Du, Juan; Yang, Hao ...
Catalysis letters,
07/2022, Volume:
152, Issue:
7
Journal Article
Peer reviewed
In the presence of KCN, the reaction of 1,10-phenanthroline (phen) with Co (ClO.sub.4).sub.2 affords a cobalt(II) complex, (phen).sub.2Co(CN).sub.2, a co-catalyst for photochemical driven CO.sub.2 ...reduction to CO. Under visible light (lambda = 469 nm), together with Ru(phen).sub.3(PF.sub.6).sub.2 as a photosensitizer and triethanolamine (TEOA) as a sacrificial electron donor, (phen).sub.2Co(CN).sub.2 shows a high selectivity (95%) for the catalytic reduction of CO.sub.2 to CO with a turnover number (TON) of 1450 during 10 h irradiation. The photocatalytic mechanism for CO.sub.2 reduction by Co(phen).sub.2(CN).sub.2 is afforded. I hope that these findings can afford a new chemical paradigm for the design of catalysts for CO.sub.2 reduction that is highly active and selective.
The thermal behavior of salts of the type Co(NH.sub.3).sub.6X.sub.3 X = Cl, Br, I has been the object of considerable interest since early in the twentieth century. As noted, some of the early ...measurements on the trichloride complex recorded what appeared to be an "anomaly" occurring in its heat capacity. Our studies, however, indicate a far more complex behavior in which (a) DSC measurements between 100 and 300 K show a glass transition at ca. 200 K corresponding to the previously-mentioned "anomaly"; (b) the glass transition is observed in both the heating and cooling cycles, but the exact details are dependent on the rate at which the process is carried out in either direction; (c) parallel crystallographic studies using samples from the same batches as those in the DSC studies document that the origin of the thermal changes are due to torsional motions of the -NH.sub.3 hydrogens about the Co-N vector, evidence of the formation of a complex structure (condis crystalline mesophase) with a variety of order-disorder (entropically-diverse) material of differing stability and mobility; (d) inasmuch as there are four independent Co(NH.sub.3).sub.6.sup.+ cations in the asymmetric unit (Z' = 3), an additional reason for the complexity of the DSC observations is due to the sequential degree of torsional disorder induced thermally during the heating cycle on each of the four individual specimens of the asymmetric unit; (e) similar behavior is observed in the cooling cycle, but, the "re-orientation" of the thermally excited -NH.sub.3 ligands to a "cooler" more-orderly condition is considerably more sluggish (hysteresis)-thus, the observed differences in the recorded rates mentioned above; (f) finally, and not surprisingly, observations carried out with different crystals of (1) the same batch and (2) different batches show the same general behavior, but the specific details vary considerably, indicating that the history (provenance) of the crystal preparation is crucial to the exact results observed in each case.
The structural (lattice metric) and elastic characteristics of a row of YBaCo.sub.4 -.sub.yZn.sub.yO.sub.7 +.sub.x cobaltites with diamagnetic dilution of the cobalt subsystem are experimentally ...studied in the structural phase transition range. For stoichiometric vacuum annealed samples, parameter DELTAa/a does not exhibit singularities during the structural transition and parameters DELTAb/b and DELTAc/c undergo jumps, which have similar magnitudes and different signs. This behavior leads to jumps in anisotropic (orthorhombic) deformation, epsilon.sub.o almost equal to -4 x 10.sup.-3, and isotropic (volume change) deformation, DELTAV/V almost equal to -1 x 10.sup.-3. Upon substitution by Zn ions, the character of structural distortion changes insignificantly and the transition temperature T.sub.S decreases linearly. The structural distortion in stoichiometric samples is accompanied by characteristic anomalies of Young's modulus DELTAE(T)/E.sub.0 and internal friction in the T.sub.S region, and the anomalies completely disappear for nonstoichiometric quenched samples. Diamagnetic substitution by Zn ions leads to a sharp decrease and then complete disappearance of the jump in the DELTAE(T)/E.sub.0 curve. This behavior can be related to a change in the relation between the isotropic and anisotropic deformations during the structural transition in the course of substitution in the cobalt subsystem.
Dual-phase membranes are increasingly attracting attention as a solution for developing stable oxygen permeation membranes. Cesub.0.8Gdsub.0.2Osub.2−δ-Fesub.3−xCosub.xOsub.4 (CGO-F(3−x)CxO) ...composites are one group of promising candidates. This study aims to understand the effect of the Fe/Co-ratio, i.e., x = 0, 1, 2, and 3 in Fesub.3−xCosub.xOsub.4, on microstructure evolution and performance of the composite. The samples were prepared using the solid-state reactive sintering method (SSRS) to induce phase interactions, which determines the final composite microstructure. The Fe/Co ratio in the spinel structure was found to be a crucial factor in determining phase evolution, microstructure, and permeation of the material. Microstructure analysis showed that all iron-free composites had a dual-phase structure after sintering. In contrast, iron-containing composites formed additional phases with a spinel or garnet structure which likely contributed to electronic conductivity. The presence of both cations resulted in better performance than that of pure iron or cobalt oxides. This demonstrated that both types of cations were necessary to form a composite structure, which then allowed sufficient percolation of robust electronic and ionic conducting pathways. The maximum oxygen flux is jsub.O2 = 0.16 and 0.11 mL/cmsup.2·s at 1000 °C and 850 °C, respectively, of the 85CGO-FC2O composite, which is comparable oxygen permeation flux reported previously.
Abstract Cobalt (Co) and its compounds are widely distributed in nature and are part of numerous anthropogenic activities. Although cobalt has a biologically necessary role as metal constituent of ...vitamin B12 , excessive exposure has been shown to induce various adverse health effects. This review provides an extended overview of the possible Co sources and related intake routes, the detection and quantification methods for Co intake and the interpretation thereof, and the reported health effects. The Co sources were allocated to four exposure settings: occupational, environmental, dietary and medical exposure. Oral intake of Co supplements and internal exposure through metal-on-metal (MoM) hip implants deliver the highest systemic Co concentrations. The systemic health effects are characterized by a complex clinical syndrome, mainly including neurological (e.g. hearing and visual impairment), cardiovascular and endocrine deficits. Recently, a biokinetic model has been proposed to characterize the dose-response relationship and effects of chronic exposure. According to the model, health effects are unlikely to occur at blood Co concentrations under 300 μg/l (100 μg/l respecting a safety factor of 3) in healthy individuals, hematological and endocrine dysfunctions are the primary health endpoints, and chronic exposure to acceptable doses is not expected to pose considerable health hazards. However, toxic reactions at lower doses have been described in several cases of malfunctioning MoM hip implants, which may be explained by certain underlying pathologies that increase the individual susceptibility for Co-induced systemic toxicity. This may be associated with a decrease in Co bound to serum proteins and an increase in free ionic Co2+ . As the latter is believed to be the primary toxic form, monitoring of the free fraction of Co2+ might be advisable for future risk assessment. Furthermore, future research should focus on longitudinal studies in the clinical setting of MoM hip implant patients to further elucidate the dose-response discrepancies.
The effect of aging (at 773 K for 1 h) on the cyclic stability of superelasticity was studied in preliminarily quenched (after annealing at 1448 K for 1 h) Nisub.44Fesub.19Gasub.27Cosub.10 ...001-oriented single crystals. It was shown that NiFeGaCo single crystals (both quenched and aged) exhibited highly stable superelasticity during more than 10sup.5 loading/unloading cycles in compression without destruction. The degradation of the superelasticity curves was divided into stages, and each stage of degradation was carefully considered. The precipitation of ω-phase particles led to a change in the degradation mechanism of superelasticity in the aged crystals. The main degradation mechanism for quenched crystals is a formation of uniform distribution of dislocations; for aged crystals, the microstructural degradation mechanisms consist of a non-uniform distribution of dislocations around the particles and the appearance of residual martensite.
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