Cobalt Source Research Articles

Tailoring the topology of ZIF-67 metal-organic frameworks (MOFs) adsorbents to capture humic acids

Chlorination is a versatile technique to combat water-borne pathogens. Over the last years, there has been continued research interest to abate the formation of chlorinated disinfection by-products (DBPs). To prevent hazardous DBPs in drinking water, it is decided to diminish organic precursors, among which humic acids (HA) resulting from the decomposition and transformation of biomass. Metal-organic frameworks (MOFs) such as zeolitic imidazolate frameworks (ZIFs) have recently received tremendous attention in water purification. Herein, customized ZIF-67 MOFs possessing various physicochemical properties were prepared by changing the cobalt source. The HA removal by ZIF-67-Cl, ZIF-67-OAc, ZIF-67-NO3, and ZIF-67-SO4 were 85.6%, 68.9%, 86.1%, and 87.4%, respectively, evidently affected by the specific surface area. HA uptake by ZIF-67-SO4 indicated a removal efficiency beyond 90% in 4 <pH< 8, while a drop was observed when pH reached ∼10. A parametric study revealed that the adsorption efficiency was a function of dosage; moreover, the removal percentage remained > 90% after 60 min mixing the solution with 0.3 g L−1 ZIF-67-SO4. Notably, an acceptable removal performance (∼72.3%) was obtained even at HA concentrations up to 100 mg L−1. The equilibrium data fitted well with the isotherm models in the order of Langmuir> Hill > BET> Khan > Redlich-Peterson> Jovanovic> Freundlich > and Temkin. The maximum adsorption capacity qm for HA uptake by ZIF-67-SO4 was 175.89 mg g−1, well above the majority of adsorbents. The pseudo-first-order model described the rate of HA adsorption by time. In conclusion, ZIF-67-SO4 presented promising adsorptive properties against HA. Further studies would be needed to minimize cobalt leaching from the ZIF-67-SO4 structure and improve its reusability safely, to ensure its effectiveness and the economy of adsorption system.

Electrochemical Oxidation of Cobalt at a Platinum Electrode in a Chloride Medium

Cobalt is a highly important metal that is widely used in lithium-ion batteries, cemented carbide, magnetic materials, chemical, and medical industries. The current global cobalt reserves (in total around 6.9 million tons) are unevenly distributed mainly between the Democratic Republic of Congo (48%) and Australia (21%) [1]. One of the main sources of cobalt is nickel production where Co is as a byproduct. Nevertheless, research related to cobalt extraction from both primary or secondary resources must be accelerated to address the current imbalance between supply and demand, that has resulted in cobalt being classified as highly critical by the EU [2]. Currently, primary and secondary raw materials are refined using pyro-hydrometallurgical or hydrometallurgical processing routes, followed by e.g. cobalt crystallization, or electrowinning. Battery grade cobalt salts can be further subjected for calcination to form battery grade oxides. In the current study, we investigate a novel approach of electrifying metallurgy - attempting for direct electrochemical cobalt recovery as cobalt oxide from a hydrometallurgical chloride based process solution.Potentiostatic electrolysis was performed in synthetic cobalt chloride solution, mimicking the industrial concentrations. SEM and EDX were used for microstructural characterization and determination of sample compositions, respectively. Cyclic voltammetry (CV) was also carried out to understand the anodic behavior of cobalt on the Pt electrode. CV studies suggested the formation of different cobalt-containing phases and the obtained precipitates in potentiostatic experiments were identified as Co3O4 and CoOOH. However, the precipitate composition was strongly dependent on the conditions of electrolysis, such as potential, temperature, and pH. At the highest studied potential (1150 mV vs. Ag/AgCl) the precipitate obtained had a saturated black color indicating desired formation of Co3O4, while at lower potentials the brown colour indicated dominance of other phases. The microstructure of the electrodes due to different potentials was investigated by SEM, indicating also morphology changes as a function of recovery potential. EDX analysis suggested that the precipitates recovered included not only cobalt and oxygen but also traces of chloride ions.Overall, this study highlights the possibility of cobalt recovery in oxide form in a chloride medium as an alternative method for the recovery of cobalt from industrial process solutions. The proposed approach can be suggested as an alternative to the traditional process of crystallization or electrowinning. In addition, cobalt obtained in a form of oxide is an important class of materials characterized by good electrochemical, catalytic, and optical properties and can be used as a final product in a variety of applications if quality requirements can be achieved. Acknowledgment The ENICON project (https://enicon-horizon.eu/) has received funding from the European Union’s Framework Program for Research and Innovation Horizon Europe under Grant Agreement No. 101058124 References Rahimpour Golroudbary, S.; Farfan, J.; Lohrmann, A.; Kraslawski, A. Environmental Benefits of Circular Economy Approach to Use of Cobalt. Global Environmental Change (2022) 76, doi:10.1016/j.gloenvcha.2022.102568.Blengini, G.A.; EL Latunussa, C.; Eynard, U.; Torres de Matos, C.; Wittmer, D.; Georgitzikis, K.; Pavel, C.; Carrara, S.; Mancini, L.; Unguru, M.; et al. Study on the EU’s List of Critical Raw Materials (2020) Final Report., doi:10.2873/904613.

Patch Testing With Nickel, Cobalt, and Chromium in Patients With Suspected Allergic Contact Dermatitis.

Background: Allergic contact dermatitis is frequently caused by metals, including multiple metals simultaneously. Objectives: To assess characteristics and associations of positive and clinically relevant patch test (PT) reactions with solitary and concurrent metal sensitization. Methods: A retrospective analysis of PT results for nickel, cobalt, and/or chromium from the North American Contact Dermatitis Group between 2001 and 2018 (n = 43,522). Results: 18.0% had a positive/allergic reaction to nickel sulfate hexahydrate, 7.3% to cobalt chloride hexahydrate, and 3.0% to potassium dichromate. 87.9% patients had a currently relevant reaction to 0, 9.4% to 1, and 2.7% to multiple metals tested. Patients with 1 versus no currently relevant reactions to metal were more likely to have a primary dermatitis site of trunk, feet, and ears; patients with currently relevant reactions to multiple metals had more dermatitis affecting the trunk and ears. Metal sources varied by co-reacting metal, especially for patients with cobalt and chromium allergy. Jewelry was the most commonly identified source of nickel and cobalt for both solitary and concurrent metal allergy. Conclusions: Sensitization to multiple metals occurred in 6% of patients. Allergen sources varied between patients with sensitivity to 1 metal versus those who had concurrent sensitivity to cobalt and/or chromium.

Enhanced electrochemical hydrogen storage performance of Co9S8 material by doping with cobalt nanoparticles embedded hollow porous carbon nanofibers

Co-axial electrospinning has been regarded as an effective technology to fabricate hollow or core/shell nanofibers. Herein, co-axial electrospinning was carried out employing polymethyl methacrylate (PMMA) and polyacrylonitrile (PAN) as the core and shell components. Cobalt acetate was used as the cobalt source. The cobalt nanoparticles embedded hollow porous carbon fibers (Co/HCNF) were obtained after electrospinning and subsequent carbonization process. For comparison, the conventional carbon fibers (CNF), hollow carbon fibers (HCNF), and cobalt nanoparticles modified carbon fibers (Co/CNF) were also synthesized. Co9S8 material was manufactured via mechanical alloying. By adjusting the types of carbon fibers, a series of carbon fibers modified Co9S8 composites were obtained by ball milling and their electrochemical hydrogen storage properties were studied. As a result, the Co9S8 + Co/HCNF electrode showed the higher discharge capacity of 603.3 mAh/g than CNF, HCNF, Co/CNF modified Co9S8 and conventional Co9S8 electrodes. The Co nanoparticles within Co/HCNF provided high electrocatalytic activity. The special hollow porous structure and high specific surface area of Co/HCNF increased the conductivity, offered more electrochemical active sites and rapid channel for charge transfer. Moreover, Co9S8 + Co/HCNF also demonstrated improved high-rate dischargeability (HRD), capacity retention and kinetics properties. An advantageous solid-solid interface may be generated between Co9S8 and Co/HCNF, serving as a beneficial electron conduction path and facilitating the hydrogen diffusion, thereby enhancing the electrode performance of Co9S8 material.

Characterization and performance of SiPM-CsI(Tl) detector for low-energy [formula omitted]- and X-ray spectroscopy

In this study, we coupled the low background CsI(Tl) crystal to a SensL J-series 60035 SiPM and detected low-energy γ and X-rays from Cobalt (57Co) and Iron (55Fe) radioactive sources. A distinct and well-resolved 5.9 keV X-ray peak was observed from the 55Fe source. The 6.4 and 14.4 KeV X-ray peaks from the 57Co source were measured and found to be very well separated from the background as well. Based on the SiPM single photoelectron peak mean value, the light output of CsI(Tl)+SiPM detector and absolute light yield of CsI(Tl) was calculated down to 5.9 keV. After correcting the reflectivity, and crosstalk factor the Absolute light yield was estimated to be 55 ± 3 ph/keV. The detector light output in terms of photoelectron per equivalent energy was calculated to be 13 ∼16PE/keVee. Furthermore, measurements of energy resolution and non-proportionality were done all the way down to the X-ray region. According to our findings, the SiPM coupled to CsI(Tl) could be an excellent detector for lower energy experiments such as dark matter searches and can be used in the study of neutrino physics as well as other high energy physics experiments.

Bamboo-Modulated Helical Carbon Nanotubes for Rechargeable Zn-Air Battery.

The high-performance and sustainable electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for rechargeable Zn-air batteries (ZABs). In this paper, a natural all-components bamboo is provided as the carbon source, and melamine and cobalt chloride are provided as the nitrogen and cobalt sources, respectively. As a result, the unique helical carbon nanotubes (HCNTs) encapsulated cobalt nanoparticles are prepared, which are acted as ORR/OER electrocatalysts to improve ZABs performance. The resultant HCNTs contribute to high ORR/OER activities via exposing more Co─N sites, providing excellent electron conductivity, and facilitating mass transfer of the reactant. The HCNTs assembled rechargeable liquid ZABs showed a maximum output power density of 226mWcm-2 and a low voltage gap of 0.85V for 330h cycles. The flexible all-solid-state ZABs achieved the maximum power density with 59.4mWcm-2 and charge-discharge cycles over 25h. The density functional theory (DFT) calculations reveal that the increase of Co─N at HCNTs effectively regulates the electronic structure of Co, optimizing the binding affinity of oxygen intermediates and resulting in the low ORR/OER overpotentials. This work paves the way for transforming renewable bamboo biomass into versatile electrocatalysts, which boosts the development of next-generation energy storage and conversion devices.

A mining industry overview of cobalt in Finland: exploration, deposits and utilization

Finland has a significant role in the European Union cobalt supply, with the largest known cobalt resources and only cobalt-producing mines in Europe. In addition, Finland is a globally significant producer of refined cobalt. However, Finland, along with the rest of Europe, is strongly dependent on cobalt imports. Recycled cobalt covers a small fraction of the country's demand, as well as that of the rest of Europe. Most of the cobalt deposits in Finland can be grouped into five genetic types (± subtypes). The orthomagmatic and Outokumpu types have been among the most important sources of cobalt in Finland. The Talvivaara type hosts the largest known cobalt resource in Europe, mostly in the Terrafame Sotkamo deposit. The most common cobalt minerals in the Finnish deposits are sulfides, and to a lesser extent sulfarsenides. These are concentrated by froth flotation, and the concentrates treated in Finnish cobalt refineries. An exception to this is the Terrafame Sotkamo mine, where bio-heap leaching technology is utilized for metal recovery, and metalliferous liquid is processed to battery-grade chemicals. Assessment of undiscovered mineral resources, prospectivity modelling, the exploration history and recent discoveries highlight the exploration potential for several types of Co-enriched mineral deposits in Finland. Thematic collection: This article is part of the energy-critical metals for a low carbon transition collection available at: https://www.lyellcollection.org/topic/collections/critical-metals

The role of supermountain belts and climatic controls on the genesis of copper deposits in the Kupferschiefer and the Central African Copperbelt

Sedimentary rock–hosted stratiform copper deposits are the world’s second largest source of copper and the largest source of cobalt, with about 73% of the copper occurring in two basins: the Katangan Basin (Central African Copperbelt) and the Permian Basin (Kupferschiefer). Why these two sedimentary basins are so highly endowed in copper is puzzling because sedimentary rock–hosted stratiform copper deposits have formed since the Paleoproterozoic and they all share remarkably similar ore mineralogy, host-rock characteristics and basin settings. We suggest that this discrepancy is due to the development of these two basins close to the bases of ~ 8000-km-long supermountain belts. The supermountain belts were instrumental in raising oxygen levels in Earth’s atmosphere, as well as providing a voluminous source of groundwater and a powerful and long-lived driver for the fluid-flow system. The elevated oxygen levels facilitated the diagenetic processes that converted copper-bearing labile minerals to amorphous iron-oxides and smectite and then in turn to hematite and illite. When oxidized brines flushed through the basin successions, the liberated copper was transported to units containing carbon-rich mudstone and the metals were deposited. For the Katangan Basin, development of the Transgondwanan supermountain belt along its margins between about 525 and 510 Ma explains the delay of several hundreds of millions of years between basin formation and mineralization in the Central African Copperbelt. In contrast, development of the Mid-Pangean supermountain belt formed penecontemporaneous with the Permian Basin explains the similarity in timing between basin formation and mineralization in the Kupferschiefer.

PSVI-30 Effects of Different Cobalt Sources on Ruminal Fermentation of Lactating Dairy Cow Diets in a Dual-Flow Continuous Culture System

Abstract The objective of this study was to evaluate the effects of different sources of cobalt in a lactating dairy cow diet on in vitro ruminal fermentation. All diets provided the same amount of supplemental Co (1 mg per kg of diet DM) included in a premix with a targeted inclusion level of 2.5% of diet DM. Treatments were cobalt carbonate (CON), and three alternative Co sources; alternative source 1 (AS1), alternative source 2 (AS2), and alternative source 3 (AS3). Eight dual-flow continuous culture fermenters were used in a replicated 4 × 4 Latin square. Experimental periods were 10 d (7 d adaptation and 3 d sample collection). Composite samples of daily effluents were collected and analyzed for NH3-N, lactate, and VFA concentration as well as for nutrient digestibility. Samples of ruminal content were collected from each fermenter at 0, 1, 2, 4, 6, and 8 h after feeding to determine lactate, NH3-N, and pH kinetics. All data were analyzed using PROC MIXED of SAS and the repeated variable of time was included for pH, lactate, and NH3-N. There were neither treatment effects nor interactions between treatment and time for pH, NH3-N, and lactate concentrations, indicating a similar Co kinetics across treatments. With regards to lactate pool, we did not observe treatment effects for L-lactate; however, we observed treatment effects for D-lactate and total-lactate as seen in Table 1. Analyses of total and individual VFA, N utilization, and nutrient degradation are still undergoing, hence, it is possible that Co sources have effects on ruminal fermentation.

Carbon Nitride Coupled Co3O4: A Pyrolysis-Based Approach for High-Performance Hybrid Energy Storage.

Graphitic carbon nitride (CN) is a cost-effective and easily synthesized supercapacitor electrode material. However, its limited specific capacity has hindered its practical use. To address this, we developed a binary nanostructure by growing nanosized Co3O4 particles on CN. The CN-Co-2 composite, synthesized via thermal decomposition, exhibited a remarkable specific capacity of 280.64 C/g at 2 A/g. Even under prolonged cycling at 10.5 A/g, the retention rate exceeded 95%, demonstrating exceptional stability. In an asymmetric capacitor device, the CN-Co composite delivered 20.84 Wh/kg at 1000 W/kg, with a retention rate of 99.97% over 20,000 cycles, showcasing outstanding cycling stability. Controlled cobalt source adjustments yielded high-capacity electrode materials with battery-like behavior. This optimization strategy enhances energy density by retaining battery-like properties. In summary, the CN-Co composite is a promising, low-cost, easily synthesized electrode material with a high specific capacity and remarkable cycling stability, making it an attractive choice for energy storage applications.

The composition and provenance of Late Bronze Age vitreous materials from Kefalonia, Greece

In this study, we present the results of the analysis of Late Bronze Age (LBA) vitreous materials from three cemeteries on the island of Kefalonia, Greece (Mazarakata, Metaxata, and Kokkolata-Menegata). A multianalytical approach (EPMA, LA-ICP-MS, MC-ICP-MS [Sr-Nd]) was used to determine the composition and provenance of a group of 14 glass beads, a glass fragment, and a faience bead, all dating to the 14th-11th centuries BCE. Most of the beads were produced using a plant ash alkali with one having a mixed alkali composition. Identification of the colorants revealed that the blue glasses were colored using Cu, Co-Cu, or Co. Cobaltiferous alum from the Western Desert of Egypt imparted the blue color to the cobalt containing glasses. Trace element and isotopic analysis showed that all the relief plaques were made using imported Egyptian glass. The isotopic signature of one relief plaque, a triple rosette motif unique to Kefalonia (K13-4), suggests that there may be greater geological variation among the currently identified LBA Egyptian silica and alkali sources or possibly the use of new raw material sources in the region. Silica and plant ashes from different regions were exploited for the manufacture of two beads of Near Eastern origin. One bead (M18-3) was made from an alkali derived from plants likely growing in river valleys in zones MP-1 (northern Iraq) or MP-3 (southern Iraq) and silica from zone MP-2 (deserts in western Iraq/eastern Syria). The other bead was unique in composition characterized by high chromium, silica from northern Iraq (zone MP-1 N), and plant ash from the desert (zone MP-2). Similarities to raw materials used to produce glass at Alalakh may tentatively suggest a similar origin. A Mycenaean Group B faience bead (Co-Cu blue) included in the study was manufactured with an alkali and a source of cobalt that did not come from the Western Desert. Further identification of the alkali type and the source of the raw materials for this faience bead was not possible but similarities were found to Group B beads from Psara and Mesara in Greece.

Facile Synthesis of Co Nanoparticles Embedded in N-Doped Carbon Nanotubes/Graphitic Nanosheets as Bifunctional Electrocatalysts for Electrocatalytic Water Splitting.

Developing robust and cost-effective electrocatalysts to boost hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs) is crucially important to electrocatalytic water splitting. Herein, bifunctional electrocatalysts, by coupling Co nanoparticles and N-doped carbon nanotubes/graphitic nanosheets (Co@NCNTs/NG), were successfully synthesized via facile high-temperature pyrolysis and evaluated for water splitting. The morphology and particle size of products were influenced by the precursor type of the cobalt source (cobalt oxide or cobalt nitrate). The pyrolysis product prepared using cobalt oxide as a cobalt source (Co@NCNTs/NG-1) exhibited the smaller particle size and higher specific surface area than that of the pyrolysis products prepared using cobalt nitrate as a cobalt source (Co@NCNTs/NG-2). Notably, Co@NCNTs/NG-1 displayed much lower potential -0.222 V vs. RHE for HER and 1.547 V vs. RHE for OER at the benchmark current density of 10 mA cm-2 than that of Co@NCNTs/NG-2, which indicates the higher bifunctional catalytic activities of Co@NCNTs/NG-1. The water-splitting device using Co@NCNTs/NG-1 as both an anode and cathode demonstrated a potential of 1.92 V to attain 10 mA cm-2 with outstanding stability for 100 h. This work provides a facile pyrolysis strategy to explore highly efficient and stable bifunctional electrocatalysts for water splitting.

A novel Co–CoAl2O4/exfoliated montmorillonite composite with improved nanoparticle dispersion for methyl orange removal via coupling peroxydisulfate

The degradation of refractory pollutants via the activation of peroxydisulfate (PDS) by Co-based nanostructures as catalysts has been gaining significant attention. However, most cobalt-based catalysts suffer from severe aggregation and metal ion leakage, resulting in a loss of activity and potential environmental threats. In this study, exfoliated montmorillonite (EMMT) loaded Co–CoAl2O4 composites were elaborately constructed through a facile coprecipitation-reduction method. The effects of the calcination temperature, the EMMT addition content, the pH of the precursor, and the reduction temperature on the microstructure of the Co–CoAl2O4/EMMT composites were investigated, and the optimum synthesis conditions were determined. In the optimal sample, well-crystallized CoAl2O4 nanoparticles were uniformly deposited onto the EMMT nanosheets with a considerably large specific surface area, while ultrafine metallic Co nanoparticles were homogeneously immobilized on the CoAl2O4 surface. This sample exhibited a superior activity (90% within 70 min) and reusability during methyl orange (MO) degradation. In the catalytic reaction, the superior adsorption property of EMMT facilitated the rapid transfer of MO molecules to the catalytically active sites. Moreover, CoAl2O4 acted as a transition layer which provided a cobalt source for the subsequent reduction process and regulated the growth of metallic Co nanoparticles, which increased the number of active sites for catalysis. Simultaneously, the metallic Co can not only activate PDS by being an electron donor, but also initiate the formation of Co-based redox pairs. This study offers new insights into the synthesis of efficient and cost-effective supported Co-based catalysts.

Triethylenediamine cobalt complex encapsulated in a metal–organic framework cage to prepare a cobalt single-atom catalyst with a high Co-N4 density for an efficient oxygen reduction reaction

Transition metal single atom catalysts (TM SACs) are the most promising oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs) and metal-air batteries. However, the low density of M-Nx active sites seriously hinders further improvement of the ORR electrocatalytic activity. Here, a strategy for encapsulating nitrogen-rich guest molecules (triethylenediamine cobalt complex, [Co(en)3]3+) was proposed to construct a high-performance cobalt single-atom catalyst (Co-encapsulated SAC/NC). With this strategy, the guest molecules are encapsulated into metal–organic framework (MOF) cages as an additional cobalt source to boost cobalt loading, while abundant nitrogen from guest molecules contributes to the formation of Co-N4 active sites. Remarkably, the resulting Co-encapsulated SAC/NC has a high cobalt loading amount of 4.03 wt%, and spherical aberration-corrected transmission electron microscopy (AC-TEM) has confirmed that most cobalt exists in a single-atom state. As a result, the Co-encapsulated SAC/NC exhibits excellent ORR catalytic performance with a half-wave potential of 0.88 V. Furthermore, Zn-air batteries employing Co-encapsulated SAC/NC as air cathode show high peak power density and excellent cycling stability. Density functional theory (DFT) calculations reveal that adjacent active sites have different rate-determining steps and lower reaction energy barriers than a single active site.

Yeast-biotemplate-assisted fabrication of self-phosphorus doped Co3O4@C hollow architecture for ciprofloxacin degradation via peroxymonosulfate activation: Performance, mechanism and toxicity evaluation

Sustainable development of highly active catalysts for peroxomonosulfate (PMS) activation to destruct organic pollutants in wastewater has irreplaceable significance, but remains a challenge. Herein, we report the successful preparation of P-doped Co3O4 integrated porous carbon hollow architecture (Co3O4@PC-HM) using spherical yeast as a natural biological template and cobalt nitrate as a cobalt source. The unique hollow microspherical structure endows Co3O4@PC-HM with large specific surface area for providing copious surface-exposed active sites, and the self-P doping facilitates the electron transfer rate, which concomitantly contribute to boosting the PMS activation for ciprofloxacin (CIP) degradation. Specifically, the Co3O4@PC-HM exhibits an excellent performance for activating PMS to degrade CIP with a removal efficiency of 95% in 20 min. Quenching experiments and electron paramagnetic resonance tests indicate the coexistence of radical and non-radical pathways in the Co3O4@PC-HM/PMS system, among which 1O2 and SO4•− play the dominant roles in CIP degradation. Simultaneously, four possible pathways of CIP degradation with the Co3O4@PC-HM/PMS system are proposed. Toxicity evaluation based on ECOSAR procedure and the growth status of mung bean roots reveal that the degradation process catalyzed by the Co3O4@PC-HM/PMS system efficiently decreases the toxicity of CIP. The natural biological template strategy has guiding significance for the synthesis of other hollow structure for versatile applications.

Facile and efficient synthesis of Pd2+@CN catalysts for enhanced phenol hydrogenation to cyclohexanone

One-step phenol hydrogenation over Pd@N-doped carbon (CN) is a sustainable approach to produce cyclohexanone, a key intermediate in the production of nylon. In this work, cobalt sources and 2-methylimidazole (2-MeIm) were mixed and directly carbonized to synthesize CN materials. After acid etching and Pd loading, the Pd2+@CN catalysts were achieved, and the porous structures and surface properties can be modulated by tuning the kind of cobalt sources and the molar ratio of 2-MeIm and cobalt. The Pd2+@CN(D) (prepared by the direct carbonization strategy) demonstrates comparable performance in the phenol hydrogenation to the ZIF-67-derived Pd2+@CN(67), and more importantly, the obtained weight of Pd2+@CN(D) is 2.1 times higher than that of Pd2+@CN(67). The optimum Pd2+@CN-4 (synthesized with a molar ratio of 4 between 2-MeIm and cobalt acetate tetrahydrate) achieves superior and durable catalytic performance (a turnover frequency (TOF) of 125.9 h−1) for the well-developed hierarchically porous structures, rich defects and abundant alkaline.

Melamine intercalation approach for the synthesis of C, N codoped net-like NiCo oxides composites and Its Application towards oxygen evolution reaction in alkaline solution

Electrolysis of water is a leading hydrogen production pathway with the advantages of simple technology, mature development and small environmental impact. However, the energy conversion efficiency seriously decreased due to the high overpotential produced by oxygen evolution reaction (OER). To decrease the overpotential of OER, NiCoOx particles with small sizes embedded in layered structure constituted with carbon and nitrogen composites (NiCoOx-CN) were prepared through melamine intercalation method with acetylacetonate as cobalt and nickel source. Finally, NiCoOx-CN showed excellent OER performance with an overpotential of only 326 mV to obtain current density of 10 mA cm−2 and Tafel slope of 70.8 mV·dec−1. Besides, NiCoOx-CN possessed excellent long-term durability in alkaline environments. Scanning electron microscopy (SEM), electron paramagnetic resonance (EPR) and other techniques were implemented to study the mechanism for the increased OER performance of NiCoOx-CN. The microstructure of NiCoOx-CN that the nanoparticles embedded into the interlinked layered nanosheets was helpful to expose more active sites. Meanwhile, the doping of C and N heteroatom and abundant oxygen vacancies also led to the enhanced conductivity of NiCoOx-CN and the optimized the electron transfer. Thus, the OER performance of NiCoOx-CN significantly boosted. As a result, this strategy holds great promise in preparing other high performance OER electrocatalysts with melamine.

The effect of gamma radiation on structural and spectroscopic properties of lithium aluminum borate glasses doped with terbium

Spectroscopic properties of fabricated Tb2O3 doped B2O3 – Li2O – Al2O3 glasses were studied before and after gamma irradiation doses 20 kGy at the rate of 3.65 kGy/hr. Non-crystalline nature of fabricated glass matrix confirmed by XRD. The obtained results were analyzed by comparing before and after radiation with the Cobalt source to study the structural variation of the sample. The Raman spectra were recorded at room temperature from 400 to 4000 cm−1 wave number range. The photoluminescence spectra at different emission and excitation wavelengths have been recorded. The variation has been discussed with respect Tb2O3 concentration

Low Detection Limit and High Sensitivity 2-Butanone Gas Sensor Based on ZnO Nanosheets Decorated by Co Nanoparticles Derived from ZIF-67.

2-butanone has been certified to cause potential harm to the human body, environment, etc. Therefore, achieving a method for the high sensitivity and low limit detection of 2-butanone is of great significance. To achieve this goal, this article uses ZIF-67 prepared by a precipitation method as a cobalt source, and then prepares cobalt-modified zinc oxide nanosheets through a hydrothermal method. The microstructure of the materials was observed by SEM, EDS, TEM, HRTEM, XPS and XRD. The test data display that the sensor ZC2 can produce a high response (2540) to 100 ppm 2-butanone at 270 °C, which is 21 times higher than that of pure ZnO materials. Its detection limit is also optimized to 24 ppb. The sensor (ZC2) also excels in these properties: selectivity, repeatability and stability over 30 days. Further analysis indicates that the synergistic and catalytic effects of p-n heterojunction are the key sources for optimizing the performance of sensors for detecting 2-butanone.

Green synthesis of cobalt oxide nanoparticles from Clitoria ternatea flower extracts its characterization and biological activities

Cobalt oxide nanoparticles (Co3O4-NPs) have numerous applications and presently the green method for the synthesis of nanoparticles is favored over other methods because of their benefits to the environment. In this study, Co3O4-NPs were synthesized by using the flower extracts of Clitoria ternatea and Cobaltous chloride hexahydrate as a source of cobalt. The synthesized Co3O4-NPs were studied by different techniques such as UV-Visible Spectroscopy, Fourier transform (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy dispersive analysis. Scanning Electron Microscopy images revealed the spherical and irregular structure of Co3O4-NPs having the particle size between 13 to 17 nm. X-ray diffraction showed the crystalline nature of cobalt oxide nanoparticles with Face – centered cubic. The prepared Co3O4-NPs showed significant antimicrobial activity against Streptococcus thermophilus, Aspergillus flavus and Aspergillus niger.