Cobalt Doping Research Articles

Synergetic effect of both cation and anion doping cobalt oxides on V2C MXene boosting oxygen evolution reaction

In order to enhance the conductivity and catalytic efficiency of non-noble electrocatalyst, an electrocatalysts consisting of ZnCo metallic double oxide with S doping embedded on V2C MXene for oxygen evolution reaction (OER) is synthesized. Cobalt serves as the primary active site, while zinc contributes to improve conductivity owing to its high electronegativity. Sulfur doping plays a crucial role in reducing the energy barrier of rate determining step of OER. The V2C MXene as a substrate can promote conductivity as well, resulting in synergistic effect. The electrocatalyst exhibits a low overpotential of 240 mV at 10 mA cm−2 in alkaline electrolyte, surpassing that of IrO2 commercial electrocatalyst. The potential shows only a minimal ∼5 mV day after 72-h stability test at 20 mA cm−2. The current density at 1.6 V vs RHE is 2 times that of commercial IrO2. Both theoretical calculation and experimental result demonstrate the advantage brought by the incorporation of zinc and sulfur. This work introduces a new idea of synergetic effect in non-noble metallic electrocatalysis.

NEXAFS and XPS Studies of Co Doped Bismuth Magnesium Tantalate Pyrochlores

Co doped bismuth magnesium tantalate with a pyrochlore structure (sp. gr. Fd-3m) was synthesized for the first time using the standard ceramic method. Single phase Bi2Mg1−xCoxTa2O9 samples were found to be formed when x < 0.7 in the X-ray phase analysis. However, with a higher cobalt content in the samples, the impurity phase β-BiTaO4 (sp. gr. P-1) is detected, and its amount is proportional to the degree of cobalt doping. The formation of solid solutions is evidenced by a uniform increase in the unit cell parameter of the Co,Mg co doped bismuth tantalate phase with an increase in the content of cobalt ions in the samples from 10.5412(8) (x = 0.3) to 10.5499(8) Å (x = 0.7). The samples exhibit a porous microstructure consisting of chaotically oriented and partially fused elongated grains measuring 1–2 μm. The dependence of the ceramic grain size on the n(Mg)/n(Co) ratio was not determined. X-ray spectroscopy (ear dge X-ray bsorption ine tructure (NEXAFS) and X-ray photoelectron spectroscopy (XPS)) was used to study the charge state of ions in Bi2Mg1−xCoxTa2O9. The NEXAFS and XPS data showed that doping with cobalt and magnesium did not change the bismuth and tantalum oxidation states in pyrochlore; in particular, the ions maintained their oxidation states of Bi(+3), Mg(+2) and Ta(+5). The energy position of the peaks of the Ta4f-, Ta5p-, Ta4d spectra had a characteristic shift towards lower energies compared to the binding energy in pentavalent tantalum oxide Ta2O5. A shift towards lower energies is characteristic of a decrease in the effective positive charge; in particular, for the Ta4f and Ta4d spectra we presented, this energy shift was ΔE = 0.65 eV, and in the region of the Ta4d edge—0.55 eV. This in turn allowed for us to assume that tantalum atoms have the same effective charge +(5-δ). The oxidation state of cobalt ions was predominantly 2+ and partially 3+, according to NEXAFS spectroscopy data.

Exploring nonlinear optical absorption in cobalt-doped Nickel–Zinc nanomaterials

This study emphasises on synthesis of ferrite nano powders via hydrothermal route within the compositional range of Ni0 65Zn0.35CoxFe(2-2x/3) O4 (x = 0.00 to 0.05 in steps of 0.01 wt%). Structural analysis via XRD and FTIR unveiled the cubic spinal structure, confirmed by signature absorption bands existence in the infrared spectra. The FESEM analysis revealed the morphological characteristics of ferrite crystals, while characterizations indicated a diminution in crystallite sizes from 53 to 37 nm. The magnetic behaviour displayed the existed correlation between Ms and Y–K angles along with finite size effects of the samples. Notably, low coercively values (0.13 Oe to 1.09 Oe) and magneto crystalline anisotropy pointed towards the magnetic quality of the ferrites with soft nature. Exhibited dielectric loss factor near 10−1, and ac-conductivity (σac) within the range of 10−5S/m to 10−4S/m of the samples indicates their improved dielectric properties. Further analysis from UV–vis. Diffuse reflectance (UV-DRS), PL spectroscopy, and Raman studies exhibits slight variations in optical band gaps, and vibrational modes due to varying cobalt doping concentrations. The evaluation of optical limiting characteristics using the Z-scan technique revealed absorption coefficients ranging from 1.40 to 4.80 × (10−10 m/W) and onset limiting values between 1.93 W/m2 and 1.11 W/m2. These findings position the Ni–Zn–Co ferrites as promising contenders for optical limiting applications owing to their optical nonlinearity and absorption characteristics.

Effect of cobalt and aluminum doping on the structural and magnetic properties of zinc oxide nanoparticles

A systematic study of the substitution effect of Co and Al on ZnO nanoparticles was carried out by x-ray diffraction (XRD) and transmission electron microscopy and using a superconducting quantum interference device magnetometer to study their structural, morphological, and magnetic properties. Zn1−xMxO (M = Co, Al) at different doping concentrations was prepared using a hydrothermal technique. The XRD results with structural Rietveld refinement reveal that the major phase of all samples had a hexagonal wurtzite crystal structure with a P63mc space group. Hysteresis loops with no magnetic saturation at high fields were analyzed at 2 K in all samples. Zero magnetic remanence and zero coercivity were also examined. The results demonstrated that the magnetic ground state at 2 K in all samples was magnetism with the coexistence of antiferromagnetic, ferromagnetic, and superparamagnetic phases. This behavior persisted at 100 and 300 K in the Al-doped sample, while Co-doped ones exhibited a paramagnetic state only. The role of non-magnetic doping, which leads to the appearance of magnetism in ZnO nanoparticles persisting at high temperatures, is discussed herein.

Layer-Number-Dependent Magnetism in the Co-Doped van der Waals Ferromagnet Fe3GaTe2.

Recently, van der Waals (vdW) antiferromagnets have been proposed to be crucial for spintronics due to their favorable properties compared to ferromagnets, including robustness against magnetic perturbation and high frequencies of spin dynamics. High-performance and energy-efficient spin functionalities often depend on the current-driven manipulation and detection of spin states, highlighting the significance of two-dimensional metallic antiferromagnets, which have not been much explored due to the lack of suitable materials. Here, we report a new metallic vdW antiferromagnet obtained from the ferromagnet Fe3GaTe2 by cobalt (Co) doping. Through the layer-number-dependent Hall resistance and magnetoresistance measurements, an evident odd-even layer-number effect has been observed in its few-layered flakes, suggesting that it could host an A-type antiferromagnetic structure. This peculiar layer-number-dependent magnetism in Co-doped Fe3GaTe2 helps unravel the complex magnetic structures in such doped vdW magnets, and our finding will enrich material candidates and spin functionalities for spintronic applications.

The Role of PbCoS Quantum Dots in Improved Photovoltaic Efficiency

<p>The quest for efficient, sustainable solar energy solutions has propelled the exploration of novel materials with enhanced photovoltaic properties. This study delves into the synthesis, characterization, and photovoltaic application of cobalt-doped lead sulfide (PbCoS) quantum dots (QDs) deposited on titanium dioxide (TiO2) substrates. Employing a hot-injection method, we synthesized PbCoS QDs and characterized their structural, compositional, and optical properties using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and UV-Visible absorption spectroscopy. The QDs demonstrated a cubic crystal structure with an average size of 20.12 nm and exhibited a direct band gap of 1.91 eV, indicative of quantum confinement effects and improved absorption in the visible spectrum. The photovoltaic performance of quantum dot-sensitized solar cells (QDSSCs) incorporating PbCoS QDs was assessed through current density-voltage (J-V) measurements, revealing a power conversion efficiency (PCE) of 2.17%. This efficiency highlights the potential of PbCoS QDs to enhance the performance of QDSSCs, partly attributed to the impact of cobalt doping on the electronic structure and photovoltaic properties of the material. The study identifies gaps in current research, such as the optimization of cobalt doping levels and the exploration of interface engineering between QDs and substrates, pointing towards future directions for enhancing the efficiency and applicability of PbCoS-based photovoltaic devices.</p>

Effect of cobalt doping on the structural and optical properties of Mn3O4 prepared by succinate coprecipitation method

Improve optical band gaps of metal oxides by a suitable doping is very interesting for optoelectronic application. However, the effect of doping is usually affected by the synthesis method. Among the existing synthesis routes, coprecipitation is cheap and offers a possibility to strictly control the stoichiometry, depending on the precipitating agents. Herein cobalt doped manganese oxides were prepared via coprecipitation using succinate ion as precipitating agent and their optical properties have been investigated. The results obtained from a set of instrumental techniques revealed that the main phase formed is Mn3O4 hausmatite with cobalt substituting manganese in the structure. The UV–visible diffuse reflectance results demonstrated that the band gap increases from 1.97 for undoped Mn3O4, to 2.91 eV for 5% Co doping, and therefore decreases to 2.34 eV for 6% Co. This trend can be explained by the difference in the substitution site of cobalt which is either tetrahedral or octahedral.

Tailoring Bandgap and Photocatalytic Performance of Designed Zinc Oxide Platelets by Cobalt Doping

AbstractPlatelet‐shaped zinc oxide (ZnO) particles exhibit certain advantages compared to conventional micron and nano forms. Their superior surface coverage and excellent optical properties make these particles very attractive as UV filters in cosmetics and personal care applications. Although ZnO is non‐toxic, it exhibits photocatalytic activity (PCA), which increases when the size of particles approaches the nanoscale. High PCA of mineral/inorganic filters is not desired in cosmetics and personal care applications. Therefore, it is essential to develop strategies to reduce PCA of such materials under UV exposure. Accordingly, the research objective of this study is to develop an understanding of the effects of Co‐doping on the optoelectronic and crystal structure of platelet shaped ZnO particles with Zn1‐xMxO stoichiometry (x=0‐4 wt % cobalt). XRD‐based Rietveld refinement and WD‐XRF reveal that Co was successfully doped into the ZnO lattice. SEM and particle size analyses confirmed that the shape and size of the designed ZnO platelets did not change significantly after doping. ~85 % reduction in PCA has was achieved by 3 wt % Co doping which was attributed to reduced OH and O2 free radical concentration. These results clearly show that Co‐doping can be used to effectively tailor the bandgap and optical properties of the designed ZnO particles.

Investigating the influence of varying cobalt doping on the cross-sectional widths and surface composition of MnOx nanowires in the context of battery–supercapacitor systems

Investigating the influence of varying cobalt doping on the cross-sectional widths and surface composition of MnOx nanowires in the context of battery–supercapacitor systems

Cobalt Doping in MOF-Derived Carbon-Loaded Tin Nanomaterials for Enhanced Electrocatalytic CO2 Reduction

Cobalt Doping in MOF-Derived Carbon-Loaded Tin Nanomaterials for Enhanced Electrocatalytic CO₂ Reduction

Spectroscopic Properties of Cobalt Ions in Ca3(VO4)2 Crystals Doped via Thermal Diffusion and During Synthesis

The spectroscopic properties of cobalt ions in Ca3(VO4)2 crystals doped via thermal diffusion and during synthesis are investigated. The diffusion doped crystal shows the potential for higher cobalt doping while maintaining its high initial optical quality. The redistribution of several absorption and fluorescence lines intensities with cobalt concentration is attributed to the formation of Co2+ optical centers with sufficiently different local environments. The fluorescence decay times of Co2+ optical centers are measured to differ by an order of magnitude (95 and 13 μs) and are attributed to centrosymmetric M1 and low symmetry M2 types of Co2+ optical centers, possibly corresponding to Ca(4) and Ca(1) positions of Ca3(VO4)2 crystal, respectively. Nonlinear transmission of Co2+ M2 centers is measured, and efficient absorption cross‐sections of 1.4 × 10−19 and 2.4 × 10−19 cm2 are evaluated at 1300 and 1500 nm, respectively. The narrow fluorescence line of cobalt ions peaking at about 1170 nm, detected in both Ca3(VO4)2 crystals doped via thermal diffusion and during synthesis, is attributed to Co ions in a trivalent state.

Study of cytotoxic performance of green-synthesized Co doped NiO nanoparticles over human breast cancer cells

The present paper presents a green method for the synthesis of pure and 1, 3, and 5% Co doped NiO nanoparticles (Co-NiO-NP) by using the aqueous extract of Salvadora persica. The synthesized nanoparticles were confirmed through PXRD, UV–Vis, FESEM, EDX, and Raman analyses. The results of PXRD, EDX, and UV–Vis affirmed the existence of well doped cobalt within the nickel oxide structure, which caused an increase in its particle size. According to PXRD finding, NiO have a face-centered cubic (FCC) structure. FESEM images showed pseudo-cubic form for nickel oxide nanoparticles which this morphology changes with doped process. Raman outcome were assigned to the longitudinal optical (LO) phonon mode of NiO. UV–Vis outcomes presented a blue shift in the adsorption peak of NiONP after the doping of cobalt ions into nickel oxide structure. According to the performed MTT test on the toxicity effect of synthesized nanoparticles on human breast cancer (MCF-7) and human umbilical vein endothelial (HUVEC) cells, cobalt doped nanoparticles displayed a higher cytotoxic activity than pure nanoparticles. Therefore, we can approve the applicability of our synthesized nanoparticles in biological implementations and cancer treatment.

Enhanced Charge Separation in Single Atom Cobalt Based Graphitic Carbon Nitride: Time Domain Ab Initio Analysis.

In recent years, single atom catalysts have been at the forefront of energy conversion research, particularly in the field of catalysis. Carbon nitrides offer great potential as hosts for stabilizing metal atoms due to their unique electronic structure. We use ab initio nonadiabatic molecular dynamics to study photoexcitation dynamics in single atom cobalt based graphitic carbon nitride. The results elucidate the positive effect of the doped cobalt atom on the electronic structure of GCN. Cobalt doping produces filled midgap states that serve as oxidation centers, advantageous for various redox reactions. The presence of midgap states enables the harvesting of longer wavelength photons, thereby extending the absorption range of solar light. Although doping accelerates charge relaxation overall, charge recombination is significantly slower than charge separation, creating beneficial conditions for catalysis applications. The simulations reveal the detailed microscopic mechanism underlying the improved performance of the doped system due to atomic defects and demonstrate an effective charge separation strategy to construct highly efficient and stable photocatalytic two-dimensional materials.

Unravelling the peculiar role of Co and Al in highly Ni-rich layered oxide cathode materials

Currently, the limited availability of cobalt resources has had a negative impact on the progress of commercial batteries, prompting the development of cobalt-free Ni-rich cathodes. However, the complete replacement of cobalt has faced challenges due to the lack of understanding the influence of dopants on cathode material performance. In this study, we aimed to address this knowledge gap by designing and preparing LiNi0.95Co0.05-xAlxO2 (x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) cathode materials. The impact of cobalt and aluminum doping on the morphology, crystallographic structure and electrothermal performance of Ni-rich cathode materials has been systematically investigated. Our findings confirmed the significant role of cobalt in increasing energy density and mitigating cationic disordering. However, it is found that cobalt doping contributes to the release of lattice oxygen during cycling, leading to rapid capacity fading. Conversely, aluminum doping could stabilize the crystal structure of the cathode material, resulting in slower capacity degradation. Furthermore, the substitution of aluminum effectively mitigates the crystal growth during the synthesis of highly Ni-rich cathode materials, leading to a reduced Li+ diffusion length and thereby excellent rate performance. Specifically, LiNi0.95Al0.05O2 could deliver a high discharge capacity of around 163 mAh g−1 at 10C. This study provides valuable insights for the design of cobalt-free Ni-rich cathodes and sheds light on the possibility of cobalt elimination.

Synthesis and Characterization of Flower-Like Cobalt-Doped ZnO Nanostructures for Ammonia Sensing Applications

Abstract The present study uses the co-precipitation method to explore the synthesis of zinc oxide and cobalt-doped ZnO sensors, encompassing a range of cobalt concentrations from 1 to 4 wt.%. The synthesized samples undergo comprehensive analysis to evaluate their structural, morphological, optical, and gas-sensing properties. X-ray diffraction revealed a hexagonal Wurtzite structure, and the crystallite size decreased from 16.92 to 15.39 nm. Energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy collectively affirmed the presence of cobalt. Scanning electron microscopy was used to analyze the morphological characteristics. The Tauc-plot was used to determine the optical bandgap via diffuse reflectance spectroscopy. As cobalt doping increased, the band gap increased from 3.18 to 3.23 eV. Further, atomic force microscopy and Brunauer-Emmett-Teller analysis were used to assess the surface topography and pore size distribution. The AFM measurements indicated roughness within 435-700 nm. The BET analysis revealed mesoporous properties, with surface area ranging between 18.657 to 21.962 m2/g. Subsequently, the gas-sensing capabilities of the Co-doped ZnO sensors were examined for various volatile organic compounds at room temperature. The sensor with 4% Cobalt doping exhibited a fast response and recovery time of 21 and 20 seconds for 2 ppm of NH3

Enhanced photocatalytic degradation by higher exposure of {110} facet and surface oxygen vacancies of BiOBr through cobalt doping strategy

Transition metal cobalt doped BiOBr (Co-BOB) was successfully synthesized by using hydrothermal method. The optimized Co-BOB achieved a remarkable rhodamine B degradation rate of 97 % in 30 min under visible light irradiation when initial concentration was 80 mg·L−1. Satisfactory removal efficiency was also observed under ambient sunlight irradiation and various water conditions. The cobalt doping strategy induced abundant surface oxygen vacancies formation (43.22 %) and resulted in an increasing exposure of {110} facets. The photosensitization and photocatalytic activities of Co-BOB significantly enhanced comparing with that of pure BiOBr. The synergy of Co doping and oxygen vacancies also induced the formation of a new band structure in Co-BOB. The synergistic effect promoted the efficient separation of photogenerated electrons and holes. By combining with density functional theory calculation, the RhB photocatalytic degradation mechanism by Co-BOB was proposed.

Study on Treatment of Ciprofloxacin in Water with Co, N Co-doped TiO2 Photocatalysts on Vermiculite

This paper presents the results of the treatment of ciprofloxacin in water with Co, N-doped TiO2 photocatalysts on a vermiculite background. Vermiculite (Ver) material after activation with HNO3 at three concentrations of 10%, 30%, and 40% exhibits a rougher surface. The 40% HNO3 activated material has the higest porosity and has a surface area greater than 79.4 times the total surface area of ​​the raw material. Co- and N-doped TiO2 photocatalysts on vermiculite were prepared by sol-gel method, using a mixture of tetraisopropylorthotitanate Ti(OC3H7)4 (TTIP), ethanol (EtOH), diethanolamine C4H11NO2 (DEA), and Co(NO3)2.6H2O. The influence of doped cobalt on the structure, surface morphology, and photocatalytic properties of N,Cox-TiO2/Ver (x=0.04;0.06;0.08 mol) was studied through scanning electron microscopy (SEM) and UV-Vis absorption spectroscopy. The SEM image shows that anatase-TiO2 crystals are evenly coated on the surface of Ver and the spherical particles are evenly dispersed on the surface of the material. The absorption spectrum shows that the band gap of the sample N,Cox-TiO2/Ver (x=0.04, 0.06, 0.08 mol) decreases from 3.32 eV to 2.64 eV. We implemented the preliminary experiments to test the efficiency of our synthesized material to treat the antibiotic ciprofloxacin in hospital wastewater. N,Co0,08-TiO2/Ver materials showed over 80% efficiency of removing the ciprofloxacin in these hospital wastewater samples.

Decreasing of Magnetic Saturation of Yttrium Doped Cobalt Ferrite Prepared by the Sol-Gel Auto-Combustion

In this research, a nano-sized cobalt ferrite material doped with Yttrium has been successfully fabricated using the sol-gel method of automatic combustion with variations in low sintering temperatures of 200, 300 and 400 °C. The results of refinement of XRD data using the Rietveld method show that the Yttrium-doped cobalt ferrite compound with a Yttrium concentration molarity of 0.1 possess a cubic crystal system and Fd-3m space group. The increasing annealing temperatures also increase the crystallite size of Yttrium-doped cobalt ferrite with the highest magnitude of 16.05 nm. The FTIR results of the samples indicated the presence of Co-O bonds around wave number 385 cm−1 and Fe-O bonds around wave number 582 cm−1 which are characteristic of the presence of cobalt ferrite compounds. From the VSM measurement results, it can be seen that there is a decrease in magnetic saturation with an increase in annealing temperature. The presence of Yttrium substitution, which takes the place of Fe3+ in cobalt ferrite material, indicates lower saturation magnetization. Image from SEM results showed samples have nanoparticle crystallite size. Evaluation of potential photocatalyst applications using a UV-Visible Spectrophotometer (UV-Vis). For Yttrium doped cobalt ferrite at 200 °C, the best degradation efficiency of Congo Red findings showed a magnitude of 76.10 %; the results are confirmed by the occurrence of the smallest crystallite size (15.11 nm). HIGHLIGHTS Preparation of yttrium-doped cobalt ferrite by the sol-gel auto-combustion method with various annealing temperatures The presence of Yttrium substitution, which takes the place of Fe3+ in cobalt ferrite material, indicates lower saturation magnetization Yttrium-doped cobalt is applied for photocatalytic Congo Red dye in water with the best performance according to the smallest crystallite size GRAPHICAL ABSTRACT

Solution‐based fabrication of copper oxide thin film influence of cobalt doping on structural, morphological, electrical, and optical properties

In this study, Cobalt (Co) doped Copper Oxide (CuO) films at different concentrations were deposited on glass substrates, using the Chemical Bath Deposition (CBD) method. The films were characterized by Field Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD), Ultra Violet-Visible Spectroscopy (UV-Vis.) and two-point contact method. The FESEM images showed that nanoplates formed increased in size and voids on the films surface decreased with increasing Co concentration. The XRD patterns revealed an increase in crystallite size with increasing (from 14.40 to 18.60 nm) Co concentration and no secondary phase was formed. The Energy-dispersive X-ray spectroscopy (EDS) spectra showed the presence of Co in the film composition with increasing concentration. The results of UV-Vis. spectroscopy showed that band gap values could be changed with Co doping and thus the CuO band gap could be adjusted with the Co doping. The temperature-dependent current-voltage measurement results obtained with the two-point contact method showed that activation energy levels increased (from 0.134 to 0.232 eV) with increasing Co concentration. It was also observed that the conductivity increased with increasing temperature.

Improvement of the ability of graphene by simultaneous cobalt (Co) and nitrogen (N) doping as an electrode for supercapacitor application

Thanks to its high electronic conductance and large surface, many research studies have investigated the application of graphene (Gr) in supercapacitors as an electrode material. The properties of Gr can change efficiently through the doping of specific elements and by designing various morphologies. In the current piece of research, DFT calculations are undertaken to investigate the impact of doping cobalt (Co) and nitrogen (N) atoms, and a monovacancy (MV)-added Gr structure upon the quantum capacitance (QC), electronic attributes and stability. Based on the calculations, doping Co and N and the presence of the MV radically changed the QC of the electrode. Nevertheless, achieving structural stability can be a challenge. A high QC of ∼77 μF/cm2 was obtained in the CoN3 system by the association of N-doping and the existence of the MV. The present piece of research provides insights into the viable impact of combined doping upon increasing the QC of Gr-based electrodes.