Cobalt Content Research Articles

Alterations in Serum Micronutrient Concentrations in North Indian Children with New-onset Type 1 Diabetes: A Case–Control Study

ABSTRACT Background: Micronutrient disturbances have long been postulated to play an etiological role in diabetes. However, data on alterations in serum micronutrient concentrations in children with type 1 diabetes (T1D) remain scarce. Materials and Methods: Serum concentrations of micronutrients (trace elements and vitamins) in children with newly diagnosed T1D were measured using standard laboratory methods. Sixty-seven children with T1D aged 1–12 years and 60 near-age- and sex-matched controls were enrolled. Results: The mean age of cases and controls was similar (7.1 ± 3.1 vs. 6.7 ± 3.0, P = 0.43). The median duration of diabetes at enrollment was 8 days (interquartile range: 4.7–27.2). Compared to controls, cases had lower manganese (2.51 ± 0.64 vs. 1.96 ± 0.48 μg/dL, P < 0.001) and higher selenium (7.68 ± 2.5 vs. 12.80 ± 17.30 μg/dL, P < 0.001) concentrations. The mean concentrations of chromium, iron, cobalt, copper, and zinc were similar in cases and controls. All measured water-soluble vitamins (thiamine, riboflavin, pantothenic acid, biotin, and folate) except Vitamin B12 and fat-soluble vitamins (A, D, and E) were lower in cases. In conclusion, the serum concentrations of several micronutrients were altered at the onset of T1D in children. Conclusions: The micronutrient disturbances at the onset of pediatric T1D may reflect the hyperglycemic state or suggest a causative role of micronutrient deficiency or excess as one of the several environmental triggers of T1D. Larger studies, especially during the presymptomatic phase, are needed to further elucidate the role of micronutrients in the onset of T1D in children.

Linking soil-metal concentrations with children's blood and urine biomarkers in Syracuse, NY.

Linking soil-metal concentrations with children's blood and urine biomarkers in Syracuse, NY.

The AAHKS Surgical Techniques & Technologies Award: Synovial Fluid Metal Ion Levels as a Biomarker for Aseptic Loosening Following Cemented Total Knee Arthroplasty: A Prospective Study.

Implant loosening following primary total knee arthroplasty (TKA) remains the most common aseptic indication for revision. Aseptic loosening can be difficult to diagnose, as radiographic findings may be absent or difficult to detect or interpret. Commercially available bone cement contains either barium or zirconium to allow for radiographic detection. We hypothesized that implant loosening leads to abrasion-related release of detectable amounts of metal ions from the implant or bone cement, which may serve as biomarkers of aseptic loosening. We prospectively enrolled 50 patients (mean age 65 years, 52% women) undergoing revision of a cemented TKA requiring component explantation. Synovial fluid was obtained prior to arthrotomy during revision surgery and analyzed for concentrations of barium, zirconium, titanium, cobalt, and chromium in parts per billion (ppb). The diagnostic utility of each ion for detecting loosening was assessed. The operative surgeon determined whether the femoral and tibial components were well-fixed or loose at the time of removal. There were 25 (50%) patients who had intraoperatively confirmed component loosening. Patients who had confirmed component loosening had elevated levels of zirconium (median levels 27 ppb versus six ppb, P = 0.016) and cobalt (median levels 16 versus 1.5 ppb, P = 0.002) compared to patients who did not have loosening. The most accurate synovial metal ion levels for diagnosing aseptic loosening were cobalt (AUC [area under the curve]: 0.76 (95% CI [confidence interval] = 0.611 to 0.92); P = 0.001) and zirconium (AUC = 0.79 (95% CI = 0.6 to 0.99); P = 0.003). In this series, barium, titanium, and chromium levels were not predictive of component loosening. Aseptic loosening remains a challenging diagnosis without an available confirmatory test. While the current sample size is limited, our results indicate that synovial fluid cobalt and zirconium levels are valuable indicators of component loosening. In the absence of definitive X-ray findings, synovial fluid analysis offers a promising diagnostic modality. This test can potentially improve patient outcomes by enabling earlier and more accurate detection of aseptic loosening following primary cemented TKA.

Modelling reactive transport of metals in Wujiang cascade reservoirs under coal-fired, hydro power generation and fishing ban scenarios.

Modelling reactive transport of metals in Wujiang cascade reservoirs under coal-fired, hydro power generation and fishing ban scenarios.

Optimization of banana midrib horn hydrolysis with cobalt-activated zeolite catalyst assisted by ultrasonic for renewable energy

This study aims to convert banana midrib into glucose using a Co-ZAA catalyst with ultrasonic assistance. Characterization was conducted through XRD and XRF analyses to determine the crystallinity, structure, and material composition. XRD results showed that the diffractogram patterns of ZAA and Co-ZAA correspond to the characteristics of mordenite zeolite based on JCPDS references. This similarity is indicated by the appearance of main peaks at 2θ, suggesting high crystallinity and optimal structural order for catalytic activity. XRF analysis revealed that Co-ZAA 15% contains silicon (55.2%) and aluminum (13%), with a Si/Al ratio that supports the material's thermal stability and acidity. The cobalt content of 18.9% confirms successful impregnation, making it an active center in catalytic reactions. Other elements, such as iron (6.16%), calcium (2.93%), and potassium (2.59%), originate from natural zeolite or synthesis residues. A qualitative test using Fehling’s reagent confirmed the presence of reducing sugars in the hydrolysis products, indicated by a color change from blue to yellow and the formation of Cu₂O precipitate. These results demonstrate that the Co-ZAA catalyst is effective in hydrolyzing cellulose into simple sugar compounds, with potential applications in biomass-based industries and renewable energy.

Evaluation of Potential Toxic Elements in Soils from Three Urban Areas Surrounding a Steel Industrial Zone

The urban zone around the city of Volos, a Greek city with a historically industrialized profile, faces threats arising from Potential Toxic Element (PTE) contamination. The scope of this study is to determine the contamination levels of 10 PTEs in three urban areas which are located near the industrial zone in the city of Volos. For this purpose, a total of 30 soil samples from parks, playgrounds and roadsides were collected from the Agios Georgios, Velestino and Rizomilos areas (Magnesia, Central Greece). The sampling was conducted in June 2022 and the concentrations of chromium (Cr), nickel (Ni), copper (Cu), arsenic (As), cadmium (Cd), lead (Pb), iron (Fe), manganese (Mn), cobalt (Co) and zinc (Zn) were measured through inductively coupled plasma mass spectrometry (ICP-MS). The Contamination Factor (CF), Pollution Load Index (PLI) and Geo-accumulation Index (Igeo) revealed moderate pollution in most cases, whereas in some sites the contamination was significant for Ni or for As. Principal Component Analysis showed concomitant changes for some PTEs in Component 1 and for others in Component 2, explaining approximately 67% of the variation. K-means Cluster Analysis showed two distinct groups of PTE-impacted sites within these urban areas. It can be postulated that industrial activities may have a carry-over effect on the soil in residential areas. Frequent monitoring of areas deemed as “contaminated” and time-series data are needed to examine in depth the soil pollution in cities and its possible shifts in relation to the changes in industrialization status in the extended urban areas.

Study Some Physical Properties of Cobalt Doped CdS Thin Films Prepared By CSP Method

In this paper, structural, morphological and optical of pureCdS and CdS:Co thin films with various cobalt concentrations were synthesized by the Chemicle spray pyrolysis (CSP) method. Hexagonal structure of CdS nanostructures with (020) preferred orientation is detected by XRD. According to morphological analysis, the doped films have homogeneously dispersed spherical grains with an average particle size of 42 nm. The optical parameters are estimated using transmittance and absorption spectra at 300-900 nm. Experimental results showed that when cobalt content increased, the band gap decreased as in

Electrochemical Performance of Layered Honeycomb Na2(Ni2-xCox)TeO6 (x = 0, 0.10, 0.25) Oxides as Sodium-Ion Battery Cathodes.

To develop economically and environmentally viable sodium-based solid-state batteries, we investigated Na2(Ni2-xCox)TeO6 (x = 0, 0.10, 0.25). After synthesizing phase-pure compositions, we confirmed P63/mcm space group and P2 coordination through high-resolution synchrotron diffraction data, where Na+ occupies three different crystallographic positions in the unit cell: Na1, Na2, and Na3. With the incorporation of cobalt into the nickel lattice, an increase in the cell volume is seen. Bond parameters show that the average Ni-Ni distance increases as a result, but the local structure and coordination do not show marked differences. Our density functional theory calculations revealed that sodium at the Na1 site is energetically more favorable and that Co doping increased the lattice constants, supported by our X-ray diffraction data. Electrochemical measurements performed on half-cells versus sodium metal using CR2032-type coin cells revealed exceptionally high specific capacity matching the theoretical value and retained around 120 mAhg-1 at the smallest but optimum concentration of cobalt. The kinetics of storage mechanisms in these compositions reflect pseudo-capacitive behavior. Our results indicate that substitution pathways in the layered oxide family of Na2Ni2TeO6 offer the potential for the development of Na-based cathodes with enhanced cycling stability and ionic conductivity.

Metal-on-metal arthroplasty, cobalt toxicity, and development of cognitive impairment: a systematic review.

Neurological dysfunction secondary to cobalt toxicity has been described as a potential complication of metal on metal (MoM) arthroplasty, however, to date the full extent of this association remains unclear. Currently, no national guideline on the management or follow-up of MoM arthroplasty patients recommends monitoring for potential insidious cognitive decline or long term consequences. The aim of this study was to summarise the available evidence regarding the relationship between MoM arthroplasty associated cobalt toxicity and cognitive impairment (CI). A systematic review of literature describing cobalt concentrations associated with neurocognitive symptoms in patients with MoM implants was undertaken. The study was registered with PROSPERO on the 18th July 2023 (CRD42023436880), in concordance with PRISMA guidelines. The Downs and Black Checklist assessed the risk of bias and evidence quality. Primary outcomes were reports of CI and blood cobalt concentration at presentation and following revision surgery. Of 361 records identified, 15 relevant publications were included. Downs and Black Checklist assessment revealed that few high-quality studies currently exist. A clear association between MoM arthroplasty and CI, across varied follow up periods, was described by all 15 studies. Mean serum cobalt concentrations at presentation of CI were 9.75ug- 625ug, however no threshold cobalt concentration was identified. Over 85% of papers which recorded post-revision outcomes reported partial, if not complete, resolution of pre-operative CI following revision surgery. This study provides the first robust systematic examination of the evidence surrounding metal on metal arthroplasty, cobalt toxicity, and potential CI. While further research is required to evaluate the exact nature of this relationship, our findings suggest that national and international guidelines should highlight the possible cognitive dysfunction secondary to MoM arthroplasty associated cobalt toxicity, including the need for routine assessment of cognitive function in those who received MoM implants.

Evaluating Heavy Metal Pollution in Nigerian Coal: Enrichment Factors, Pollution Indices and Environmental Implications

Heavy metal pollution is a significant environmental concern in Nigeria, particularly in coal deposits. This study evaluates the level of heavy metal pollution in Nigerian coal deposits using enrichment factors and pollution indices. Coal samples were collected from Maganga, Gboko, Onyeama, Okobo, Opoko-Obido, Odagbo and Ofugo coal fields, and the concentrations of lead, arsenic, chromium, manganese, nickel, cobalt, strontium, antimony and barium were determined. The results showed significant levels of heavy metal pollution, with enrichment factors indicating anthropogenic sources. Pollution indices reveal moderate to high levels of pollution. The study highlights the need for effective environmental management and pollution control measures to mitigate the environmental and health risks associated with the heavy metal pollution in Nigerian coal deposits.

Cobalt modulates methanol turnover of the alcohol dehydrogenase in Desulfofundulus kuznetsovii strain TPOSR.

Desulfofundulus kuznetsovii strain 17T oxidizes methanol via a two-pathway system involving both alcohol dehydrogenases (ADH) and a cobalt-dependent methanol methyltransferase (MT). In contrast, D. kuznetsovii strain TPOSR lacks the MT pathway, relying solely on ADH for growth on methanol. Despite the absence of the MT pathway, cobalt starvation resulted in lower methanol uptake rates and reduced growth rates in strain TPOSR, suggesting a critical role of cobalt in methanol metabolism outside of its role in the MT system. Given the often-crucial role of metal cofactors such as iron, zinc, and other metals in the active site of ADHs, we hypothesized that cobalt could influence the catalytic activity of the TPOSR ADHs. The gene encoding for the most abundant ADH during growth on methanol, Adh1, was heterologously expressed in Escherichia coli, and the enzyme was purified for kinetic studies. Adh1 exhibited optimal activity at 55°C and is oxygen tolerant. The methanol turnover rate increased from 1.76 (95% Cl [1.56, 1.99]) s⁻¹ to 3.5 (95% Cl [3.3, 3.72]) s⁻¹ with the addition of 2 µM CoSO4, while higher cobalt concentrations (>5 µM) inhibited Adh1 activity. Similarly, NiSO4 addition (1-1000 µM) enhanced Adh1 activity, with a 75% improvement observed at an optimum concentration of 200 µM. Our findings suggest that the importance of cobalt for the methanol metabolism of sulfate-reducing organisms extends beyond its involvement in the MT system.IMPORTANCEMethanol is a ubiquitous compound in natural environments, where it is produced geothermally or from plant and microbial biomass. Its microbial metabolism is particularly important in low-nutrient, oxygen-free environments, such as the deep subsurface, where specialized microbes compete for methanol and play a crucial role in the global carbon cycle. Typically, microbes in these settings rely on a cobalt-dependent methanol methyltransferase (MT) pathway for methanol breakdown. However, Desulfofundulus kuznetsovii TPOSR deviates from this, lacking the MT pathway and instead relying solely on alcohol dehydrogenases (ADH) to oxidize methanol. Despite the absence of the cobalt-dependent MT system, our study shows that cobalt strongly stimulates the activity of the most abundant ADH, revealing an unexpected, yet significant role for cobalt in this alternative methanol metabolism. Understanding these interactions not only sheds new light on methanol metabolism in nature but also opens up possibilities for developing more efficient and sustainable technologies for methanol conversion in industry.

Factorial Design and Optimization of Trimetallic CoNiFe-LDH/Graphene Composites for Enhanced Oxygen Evolution Reaction.

Layered double hydroxides (LDH) have exhibited promising applications as electrocatalysts in oxygen evolution reactions (OER). In this work, trimetallic LDHs (CoNiFe-LDH) were designed and grown on graphene (G) through a one-step hydrothermal approach to obtain a structure that promotes efficient charge transfer. A 2-level full-factorial design was utilized to evaluate the effects of varying the concentrations of Co (1.5, 3, and 4.5 mmol) and graphene (10, 30, and 50 mg) on the OER activity. The potential needed to deliver 10 mA cm-2 was chosen as the response parameter. The independent and dependent parameters were fitted to a linear model equation through ANOVA analysis. The computed p-values were below 0.05 signifying the statistical significance of the concentrations of cobalt and graphene and their interaction, suggesting a correlation with the OER activity. The OER experiments were conducted in triplicate using the Co[3]Ni[3]Fe[3]-LDH/G[30] (central point) to estimate variability (0.58%). Comparative analysis showed that Co[1.5]Ni[3]Fe[3]-LDH/G[10] achieved the lowest onset potential (1.54 V), potential at 10 mA cm-2 (1.58 V), and Tafel slope (58.4 mV dec-1), indicating that a low concentration of cobalt and graphene make an efficient electrocatalyst for OER. Furthermore, the optimized composite demonstrated favorable electronic properties, with a charge transfer resistance (RCT) of 188.1 Ω, and exhibited good stability, maintaining its catalytic activity with no significant loss over a 24-h period.

Contribution of Zn–Co Alloys Coatings Study: Electrodeposition Methodology, Micromechanical Properties, and Tribological Behavior

: An overview of the literature reveals that electrodeposition baths significantly influence deposited coatings’ morphology and properties. The present study investigates a sulphate-based bath in terms of the additive, pH, and temperature for the electrodeposition of Zn–Co alloys onto mild steel, achieving a nanocrystalline structure. The obtained results of the cyclic voltametric and SEM analyses revealed that sodium allowed the enhancement of cobalt electrocrystallisation (22.6 wt%) to homogenize further layers’ structure. However, the adjustment of pH allowed for the obtention of deposits with a refined structure containing only 5 wt% cobalt. Although an increase in room temperature resulted in deposit coatings with the same cobalt content, it notably produced a smoother structure. Subsequently, Zn–Co coatings were compared to pure zinc layers in terms of micromechanical and tribological behaviour. The morphology shifted from hexagonal platelets to nodular structures with the incorporation of cobalt, leading to an increase in microhardness. The morphology transformation, coupled with micromechanical reinforcement, contributed to the mitigation of friction and the improvement of the wear resistance of zinc layers through cobalt alloying. In fact, this improvement enhances the performance of zinc-coated applications in automotive and aerospace industries, particularly for standard assembly components that require adequate resistance to wear and abrasion during handling and tightening.

Concentration of cobalt in IOCG systems: Exemplified by the Proterozoic Kangdian IOCG metallogenic province, SW China

Concentration of cobalt in IOCG systems: Exemplified by the Proterozoic Kangdian IOCG metallogenic province, SW China

Electrodeposition of Ni-Co thin films from ammonia-chloride electrolyte

This study presents the research results on the co-deposition of nickel and cobalt from an alkaline electrolyte containing glycine. For this purpose, cyclic and linear polarization curves of co-deposition were obtained at various cobalt concentrations, different poten-tial sweep rates, and electrolyte temperatures. It was established that the co-deposition process occurs anomalously, with the cobalt content in the deposited films exceeding that of nickel. The deposits obtained under optimal conditions contained 37.25 % Ni and 51.43 % Co. The study of the effect of the potential sweep rate on the co-deposition process of nickel and cobalt revealed a linear relationship between the current peak value and the square root of the potential sweep rate. This indicates that the initial stage of Ni-Co co-deposition is controlled by the diffusion of the metal ions to the cathode surface. When recording polarization curves on a rotating disk electrode at different rotation speeds, the relationship between the current peak value and the square root of the electrode rotation speed was also linear at relatively low rotation speeds. However, at higher rotation speeds, the process was controlled by electrochemical polarization. The co-deposition of Ni with Co was confirmed through X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses. The investigation of the catalytic activity of Ni-Co deposits in a neutral medium (0.5 M Na₂SO₄) demonstrated that the amorphous thin films, not subjected to annealing, exhibited the best electrocatalytic properties for the hydrogen evolution reaction. The Tafel slope was determined to be 118 mV dec-1.

Microstructure and mechanical properties of NiCoCrMoW medium-entropy alloys via controlling of cobalt content and Al/Ti co-doping

Microstructure and mechanical properties of NiCoCrMoW medium-entropy alloys via controlling of cobalt content and Al/Ti co-doping

MACROMYCETES AS INDICATORS OF ANTHROPOGENIC POLLUTION OF FOREST ECOSYSTEMS WITH HEAVY METALS

Mycobiota is a group of living organisms characterized not only by high resistance to anthropogenic factors, but also by the ability to accumulate such substances as heavy metals. This property allows the use of certain macromycetes in environmental monitoring of forest ecosystems. Objective. The aim of the study is to determine the influence of abiotic and anthropogenic factors on the accumulation of heavy metals by fruiting bodies of macromycetes. It can help to assess the forest ecosystem pollution by pollutants in the Middle Volga region. Materials and Methods. Fruiting bodies of dominant macromycetes (soil and wood-destroying fungi) were studied in forest ecosystems with different levels of anthropogenic load. Lead, nickel, copper, cadmium, zinc, cobalt and iron content was determined. The sampling areas were the park of Ulyanovsk city “Vinnovskaya grove”, a site in the Ulyanovsk forestry (2 km from Ulyanovsk) and a site in the Kuzovatovo forestry (100 km from Ulyanovsk, control). The sample areas were of a similar forest site type. Results. It was revealed that among ecological groups of macromycetes, the sorption capacity in relation to the total amount of heavy metals is most clearly expressed in mycorrhiza-forming fungi. In the evolutionary development, a decrease in the content of pollutants was observed as we move from obligate saprotrophs to obligate parasites, i.e. from evolutionarily old to evolutionarily young species. Under the increasing impact of the anthropogenic factor, HM Accumulation in soil fungi is more intensive than in wood-destroying ones. It is explained by the type of substrate on which the fungi grow. In the ecological chain “soil - wood - tinder fungus” an increase in the content of heavy metals is observed as we move from saprotrophs to the highest trophic link of consumers.

BIOACTIVE COMPOUNDS AND HEAVY METALS CONTENT IN CASCARA COFFEA ARABICA

The primary aim of the scientific article is to comprehensively analyze the chemical composition of Cascara. This study investigates the physicochemical properties of Cascara (100% Coffea arabica) sourced from America (Colombia, Panama, Costa Rica, Brazil, Guatemala). The cascara samples were analyzed for dry matter content, pH, water activity, polyphenol content, antioxidant capacity, chlorogenic acids profile, caffeine content and heavy metals (copper, zinc, manganese, iron, nickel, cobalt, lead, cadmium) concentrations. Our results revealed significant variations among the samples. Dry matter content ranged from 85.46% to 88.49%, with the highest levels found in the Guatemala sample (5C). pH values varied significantly, from 3.58 in the Colombian sample (1C) to 4.50 in the Brazilian sample (4C). Water activity was lowest in the Colombian sample (0.49) and highest in the Guatemala sample (0.55). In terms of bioactive compounds, chlorogenic acids content was highest in the Guatemala sample (0.97 mg.100 g-1), while the highest caffeine concentration was detected in the Costa Rican sample (2.22 mg.100 g-1). The total antioxidant capacity was highest in the Brazilian sample using the DPPH method (84.635%) and in the Panamanian sample using the ABTS method (92.30%). Heavy metal analysis indicated significant differences, with the highest concentrations of copper (10.13 mg.kg-1) and iron (112.09 mg.kg-1) in the Costa Rican sample, and the highest zinc (5.17 mg.kg-1) in the Panamanian sample. The lowest concentrations of nickel (0.07 mg.kg-1) and cobalt (0.24 mg.kg-1) were found in the Colombian sample. The presence of lead and cadmium, particularly in American samples, highlights potential health risks, necessitating stringent monitoring. A strong positive correlation was found between neochlorogenic acid concentration and total phenolic content (TPC) (r = 0.84) and between neochlorogenic acid concentration and manganese (Mn) presence (r = 0.83). Concentrations of nickel (Ni) and cobalt (Co) (r = 0.920) and Pb and Cd (r = 0.74) also demonstrated strong correlations. Detailed knowledge of Cascara’s chemical composition can aid in the development of new food and beverage products. This can expand the market for Cascara, promoting sustainability by utilizing coffee by-products more effectively.

The resistance of biohumus microbiome to cobalt and nickel compounds

Heavy metals, particularly cobalt and nickel, are highly toxic and widely distributed in ecosystems. Sometimes, their concentration in natural ecosystems can increase sharply due to anthropogenic activities. Metal-resistant microorganisms are considered to be promising for their detoxification. The purpose of the work was to study the sustainability of microorganisms derived from the biohumus in the presence of toxic cobalt and nickel compounds as well as determine the maximum limit concentration of Co2+ and Ni2+ for them. The biohumus served as a model natural ecosystem free from heavy metals where microorganisms were not adapted to them. The resistance of microorganisms was determined by cultivation in the medium with a gradient of simultaneous Co2+ and Ni2+ from 0 to 1000 mg/L. The quantification of Co2+ and Ni2+-resistant microorganisms in the biohumus was determined by counting the number of colony forming units on nutrient agar. Using a Niton XL5 Plus manual XRF analyzer, it was determined that in metal missile fragments the concentration of cobalt ranged from 73 ± 22 to 589 ± 34 mg/kg, the concentration of nickel was 110 ± 15–577 ± 21 mg/kg. Cobalt was not detected in all soil samples. Nickel compounds were detected in two samples of the affected soil up to 408 ± 8 mg/kg and 36 ± 4 mg/kg in soil without shell explosions. On the example of the microorganisms of the biohumus, we confirmed that natural ecosystems contain microorganisms resistant to toxic Co2+ and Ni2+ compounds in high concentrations. The concentrations of simultaneous Co2+ and Ni2+ of 100 and 200 mg/L were established not to affect the growth of microorganisms, and the number of CFUs was (6.2 ± 0.2)×105 and (6.1 ± 0.2)×105 CFU/g. The maximum permissible concentration of simultaneous Co2+ and Ni2+ for the biohumus microbiome was 700 mg/L and the number of CFUs was (5.0 ± 0.1)×102 CFU/g after a month of cultivation. Moreover, microorganisms can adapt and maintain sustainable growth even after the increase in the concentration of metals from 500 to 2500 mg/L as well as to provide the detoxification of divalent metals by transforming into insoluble non-toxic sulfides.

Impact of Co2+ substitution by Fe2+ on the thermal behavior of a hydrated fluoride, precursor of a mixed iron-based oxyfluoride with reduced cobalt content as efficient OER electrocatalyst

In a sustainable development objective, it is necessary to consider both the performance and the preciousness of metals for the development of new catalysts. In this way, this work aims to reduce the amount of cobalt in the mixed Co–Fe oxyfluoride Co0.5Fe0.5O0.5F1.5, obtained from the thermal degradation of the hydrated fluoride precursor CoFeF5(H2O)7, while maintaining its electrocatalytic performance as an electrocatalyst for the Oxygen Evolution Reaction (OER) in alkaline media. To achieve this, the proposed strategy consists in substituting the Co2+ ions by Fe2+ ions in CoFeF5(H2O)7, chosen for its earth abundance, leading to the solid solution (Co1–xFex)2+Fe3+F5(H2O)7 obtained by co-precipitation. This series of hydrated precursors was then subjected to a thermal treatment in ambient air in order to obtain the corresponding solid solution of the oxyfluorides Co(1–x)/2Fe(1+x)/2O(1+x)/2F(3–x)/2. Structural and thermal analyses confirm a Co2+/Fe2+ substitution in hydrated fluoride precursors, while those of calcined samples indicate a complex thermal decomposition leading to Co–Fe oxyfluorides. The OER electrocatalytic performance of these oxyfluorinated materials shows that it is possible to reduce the amount of cobalt by up to 20% without affecting the overall OER activity, namely an overpotential of 320 mV at 10 mA·cm–2 and a mass activity of 112 A·g–1 at 1.55 V vs. RHE, with high stability.