Cobalt Doping Research Articles

Evaluating the effect of A- and B-site cobalt doping on the structural, morphological, dielectric, and non-ohmic properties of CaCu3Ti4O12 ceramics prepared by the hydrothermal method

CaCu3Ti4O12 (CCTO), CaCu3-xCoxTi4O12 (CCCxTO) and CaCu3Ti4-xCoxO12 (CCTCxO) ceramics with x = 0.1 were synthesized by the hydrothermal process at 200°C for 24 hours. The influence of cobalt substitution on the copper and titanium sites in CaCu3Ti4O12 on the structural, morphological, and physical properties was investigated. It was shown through the analysis of X-ray diffractograms of CCTO, CCCxTO, and CCTCxO compounds that they crystallized in a pure perovskite structure without the presence of secondary phases. The refinement of the spectra using the Rietveld method showed an efficient formation of the crystalline phase of the cubic structure (Im3¯), which remains unchanged, with an increase in the unit cell due to the substitution of Co2+/Co3+ in the Cu2+ and Ti4+ sites of the CCTO ceramic. Raman spectroscopy was used as a complementary characterization method to XRD in order to detect vibrational bands and highlight any changes in the crystal lattice. SEM results showed that cobalt insertion increased the average grain size. The dielectric properties were studied by complex impedance spectroscopy in a frequency range from 1 kHz to 1 MHz at different temperatures, where the insertion of cobalt in the Cu2+ and Ti4+ sites has a significant effect on the permittivity value (εr) and dielectric losses (tanδ). The non-ohmic characteristics showed that the change in grain size due to cobalt incorporation is beneficial to improving the breakdown strength (Eb) and nonlinear coefficient (α), which can be attributed to the grain boundary properties of the Internal Barrier Layer Capacitor (IBLC) model and the behavior of the Schottky barrier.

Enhanced NOx-assisted soot combustion by cobalt doping to weaken mullite Mn-O bonds for lattice oxygen activation

Enhanced NOx-assisted soot combustion by cobalt doping to weaken mullite Mn-O bonds for lattice oxygen activation

Experimental and calculation investigations of the photocatalytic selective and performance for CO2 reduction by cobalt-doped Bi4O5Br2 nanosheets

This study delves into the photocatalytic process of an innovative Co-doped Bi4O5Br2 material synthesized through a straightforward process. Experimental and theoretical findings corroborate that cobalt doping remarkably enhances the CO2 reduction capability of Bi4O5Br2 catalysts under visible light. Findings indicate that Co-doped Bi4O5Br2 exhibits substantial advantages over its pristine counterpart in photocatalytic CO2 reduction. Notably, the catalyst with 4 at.% Co doping demonstrates the highest photocatalytic CO2 reduction efficiency, achieving CO and methane production activities of up to 9.46 and 0.20 μmol/g/h, respectively. Furthermore, the low activation energy for CO2 reduction in Co-doped Bi4O5Br2, as indicated by reaction pathways calculations, facilitates the process. Detailed experimental results reveal that Co incorporation does not alter the surface morphology or the crystalline phase of the photocatalyst. The superior efficiency of Co-doped Bi4O5Br2 is attributed to multiple factors: a narrow band gap, expanded visible light absorption spectrum, greater absorption intensity within the visible range, and enhanced separation efficiency of photogenerated electrons and holes compared to pristine Bi4O5Br2. This highlights the practical application of Co-doped Bi4O5Br2 for enhancing photocatalytic performance, supporting future advancements in solar energy utilization and the creation of high-value chemical products.

Enhanced electrochemical characteristics of MnO anode induced cobalt dopant for Li ion batteries

Enhanced electrochemical characteristics of MnO anode induced cobalt dopant for Li ion batteries

Electrochemical performance of cobalt-doped NiO thin films synthesized by spray pyrolysis

ABSTRACT In this work, various cobalt-doped NiO thin films have been synthesized via the spray pyrolysis. The cobalt-doped NiO thin films show a cubic phase with preferred orientation along the (111) plane. The scanning electron microscopy images of the cobalt-doped NiO thin films show interconnected flakes with small agglomerated particles. The optical bandgap decreases from 3.30 eV for the undoped NiO thin film to 2.90 eV for 20 mol% cobalt doping, with an increase in cobalt doping concentration in NiO. The electrochemical activities have been tested in 2M KOH electrolyte with cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The highest specific capacitance observed for the 10 mol% cobalt-doped NiO thin film electrode is 760 Fg−1 at a scan rate of 5 mVs−1. The 10 mol% cobalt-doped NiO thin film electrode shows 92% retention in capacitance after 1000 cycles and a low charge transfer resistance of 10 Ωcm2.

Synthesis of mesoporous cobalt-doped MoO3 nanoribbons for highly selective detection of triethylamine

Co-doped MoO3 nanobelts are successfully synthesized as model materials by MOF derivatization method, and the gas sensing performance towards TEA as well as the sensing mechanism are studied. In particular, the MCo-MoO3-450 sample exhibits the best TEA sensing performance at 110 °C, with superior anti-interference ability and high sensing response (Ra/Rg = 361.62, 50 ppm). It is noteworthy that the improvement of TEA sensing performance can be achieved by adjusting the processing temperature to control the Co2+/Co3+ ratio. This work offers a dependable approach for the production of cobalt-doped MoO3 nanobelts and demonstrates that cobalt doping is a viable tactic for designation of high-performance TEA sensors.

Boosting low-temperature NH3-SCR performance via mixed-valence cobalt dual active sites

Nitrogen oxides (NOx) have become a critical environmental concern, necessitating the development of highly efficient catalysts for temperature which is lower than 300 °C. Selective catalytic reduction with NH3 (NH3-SCR) is a process where ammonia is the reducing agent for selective catalytic reduction of nitrogen oxides in exhaust gases. The mechanism-property relationship between catalytic active sites and low-temperature denitrification efficiency, however, remains unclear. In this study, we synthesized a series of cobalt-modified nanoparticle catalysts using a scalable citric acid sol-gel method and conducted comprehensive characterizations. Our findings indicate that an optimal cobalt doping rate significantly enhances catalytic activity due to the synergistic effects of reduced nanoparticle size and the dual active sites of Co0/Co2+. Specifically, at a cobalt doping ratio of 1.0, the catalyst demonstrates peak SCR activity, achieving 85.5% NOₓ conversion at 120 °C and complete conversion at 150 °C. These cobalt-modified nanoparticle catalysts feature high deposition of doped Co ions on their surfaces, predominantly as metallic cobalt and CoOx nanoclusters. Compared to undoped samples, the cobalt-doped nanoparticle catalysts exhibit a greater specific surface area, increased acidity, enhanced chemisorbed oxygen, and improved redox properties, all contributing to superior denitrification efficacy. Additionally, Density Functional Theory (DFT) calculations provide assertive evidence into the reaction mechanism, showing that Co2+ sites effectively adsorb and activate NH₃, while Co0 sites are crucial for NO adsorption and activation. The synergistic interaction between Co2+ and Co0 facilitates NN coupling, enhancing overall reaction efficiency. These findings underscore the potential of cobalt-modified catalysts for practical industrial applications, offering robust performance over a wide temperature range and meeting stringent environmental regulations.

Tailoring of magnetic phase: Co-doped SiC thin films grown by RF sputtering

In the present work, we investigate the influence of cobalt (Co) doping on the structural and magnetic properties of cobalt-doped silicon carbide (Co-SiC) thin films. The films were fabricated using DC/RF magnetron sputtering technique on Si (100) substrates at a temperature of 1200°C, with varying Co concentrations ranging from 5 to 16 at. (at%. X-ray diffraction (XRD) analysis unveiled the co-existence of CoSi2 and SiC phases in all the thin films. Surface morphological study through atomic force microscopy (AFM) revealed the densely packed nature of the films. Field emission scanning electron microscopy (FE-SEM) study showed that particles are uniformly distributed at the surface of the substrate. According to UV measurements, the films have high transmittance in the visible range, and as Co concentration rises, transmittance decreases. A magnetic phase transition from superparamagnetic to ferromagnetic behavior occurred with Co content surpassing 8 at% in the SiC thin films. Moreover, an increase in coercivity was observed from 38 Oe to 316 Oe as the doping concentration increased from 10 to 16 at%. This study represents an exploration into the induction of ferromagnetism through moderate Co doping in SiC thin films.

Electronic structure regulation of Cu-based Ruddlesden-Popper perovskites by cobalt doping for enhanced degradation of oilfield fracturing wastewater in electrocatalytic peroxymonosulfate system

Purification of oilfield fracturing wastewater is the most challenging type of oilfield wastewater treatment. In this work, a heterogeneous electrocatalytic peroxymonosulfate (PMS) system was established to treat oilfield wastewater using Co-doping induced Cu-based Ruddlesden-Popper (RP) perovskites as catalysts. Characterization results illustrated that the obtained catalysts were generated the heterojunction of LaCoO3/La2CuO4 and the Co would transfer electrons to Cu, resulting in a higher chemical oxygen demand (COD) degradation efficiency (> 80 %) of oilfield fracturing wastewater under the neutral environment. Singlet oxygen (1O2) played the main function for COD removal with analysis results of reactive oxygen species (ROS). Experimental results and theoretical calculations indicated that the reduction effect of carbon felt (GF) cathode and the redox cycle of Cu(I)/Cu(II) and Co(II)/Co(III) accelerated the activation of PMS. Moreover, the lattice oxygen participated in the generation of ROS. Significantly, the LaCoO3/La2CuO4 heterojunction displayed a higher total density of states (TDOS) value near the Fermi level, implying their favorable electron transfer for PMS activation. This study opens new avenue for resolving the challenge of oilfield fracturing wastewater pollution.

Promoting elemental mercury immobilization performance from smelting flue gas over a wide temperature range via cobalt-doped copper sulfide adsorbents

Copper sulfide (CuS) sorbent exhibits great potential for gaseous elemental mercury (Hg0) decontamination, but it still suffers from a narrow operating temperature. Therefore, designing advanced CuS sorbents that have a high activity level for capturing Hg0 and thermal stability at a high temperature range is challenging. Herein, we propose a metal doping strategy to fabricate a bimetallic sulfide adsorbent. Benefiting the unique structure and composition, a mesoporous structure and an abundance of unsaturated sulfur sites ensure that CuxCo(1–x)Sy provides a desirable level of adsorption for Hg0. The experimental results indicate the optimum Co doping mass concentration of 5 %. The Cu0.95Co0.05Sy not only performs satisfactory Hg0 adsorption at elevated temperatures (Hg0 average adsorption efficiency of over 97.3 %, Hg0 average adsorption rate of over 2.7 μg/g/min), but also presents an exciting regeneration and recycle performance (a Hg0 adsorption efficiency of over 94 % after 10 cycles). The adsorption capacity of Cu0.95Co0.05Sy at the breakthrough threshold of 25 % reaches 5.22 mg/g, surpassing most of metal sulfide sorbents for Hg0 immobilization at 150 °C. As far as Hg0 adsorption is concerned, the composition of typical smelting flue gases has almost no effect. According to further studies, unsaturated coordination short-chain sulfur (S22−) sites are essential for adsorption of Hg0 and are capable of directly forming α-HgS from Hg0. In both the contrast experiment and density functional theory calculations, the cobalt doping strategy enhances the thermal stability of the active S22− ligand and the Hg0 adsorption properties. This study not only provide a prospective adsorbent for Hg0 sequestration at wide temperature range, but also explores a method of utilizing gaseous contaminants for resource utilization.

The interplay between optoelectronic and magnetic properties in Co-doped Cu2ZnSnS4 for next-generation solar cell devices

Abstract A search for next-generation solar cell devices to massively actualize renewable energy is being exponentially conducted. It includes the development of Cu2ZnSnS4 (CZTS)-based solar cells, which are known as cost-effective and highly stable solar cell devices. In this present research, we develop a CZTS solar cell by adding a magnetic degree of freedom using cobalt (Co) doping. We find that the Co doping can induce modulation of the crystalline structure and bandgap of CZTS, which further influences its photovoltaic performance. The increase in the grain size of the CZTS with the addition of Co doping could further induce the reduction of detrimental grain boundaries, which benefits the photovoltaic performance of CZTS-based solar cells. Co doping also generates magnetic behavior in CZTS, which supports its magnetically controlled optoelectronic properties and thus, in turn, enhances the photovoltaic performance. We believe that this study could open up opportunities to obtain next-generation solar cell devices with excellent performances by using magnetic-field induction.

Cobalt-doped molybdenum sulfide as an interlayer facilitates polysulfide conversion to obtain high-performance lithium−sulfur batteries

Lithium–sulfur (Li–S) batteries are considered to be a promising energy storage system due to their theoretical specific capacity. However, the “shuttle effect” of polysulfides (LiPSs) and the slow redox kinetics of LiPSs in the conversion reaction have hindered their large−scale application. In this study, the Co-MoS2 is prepared and coated on the polypropylene (PP) separator of Li–S batteries. The Co elements are successful addition and uniform distribution in the Co-MoS2. This coating is designed to provide chemical adsorption and catalysis for LiPSs. Consequently, Li–S batteries with a Co-MoS2 interlayer exhibit outstanding long-cycle and high-rate performance. After 500 cycles at 0.5C, the reversible capacity is found to be 561 mAh g−1, with only a low-capacity reduction of 0.097 % per cycle. Furthermore, 602 mAh g−1 is delivered even at 4C. The results of electrochemical measurements and first principles calculations demonstrate that the high performance of Li–S batteries is attributed to the chemical adsorption and electrocatalysis roles of the Co-MoS2 interlayer, which inhibit the “shuttle effect” and enable fast redox reaction kinetics. In addition, the introduction of cobalt doping results in the formation of the 1T phase of MoS2, which enhances the conductivity of the Co-MoS2. The presence of plentiful cobalt-doped MoS2 defects provides abundant catalytic sites for the electrochemical reaction of LiPSs.

Efficient photo-Fenton-like degradation of tetracycline hydrochloride using Co-In2O3 nanotubes: Insights into mechanism and performance

Photo-Fenton-like process is effective towards refractory organics removal for its strong oxidation capacity. Herein, cobalt-doped indium oxide (Co-In2O3) with nanotube morphology was prepared and was taken as photo-Fenton-like catalyst. In the presence of peroxymonosulfate (PMS), Co-In2O3 nanotubes exhibited excellent photo-Fenton-like activity with tetracycline hydrochloride (TC-HCl) degradation of 98.8 % in 40 min. The visible light driving Co-In2O3/PMS system showed the reaction rate constants of 0.0998 min−1, which was 6 folds of the In2O3/PMS/vis system. Experimental results combining with theoretical chemical calculation demonstrated that the doping of Co can effectively reduce the band gap of In2O3, thus leading to stronger visible light absorption capability. The presence of oxygen vacancies (OVs) disrupted the symmetry and integrity of the catalyst structure and achieved electron enrichment at the reactive site. Simultaneously, Co doping and an appropriate amount of OVs strengthened chemisorption for PMS (from −0.652 eV to −4.224 eV) and higher electron density difference (from 0.49 e– to 0.68 e−). Our findings provide insight on the contribution role of cobalt doping and OVs in improving photo-Fenton-like catalytic efficiency.

Cobalt-doped copper sulfide nanocomposite integrated with graphene oxide as a high-performance conversion anode for aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) encounter substantial obstacles arising from the inherent dilemmas of dendrite growth, hydrogen gas evolution, and corrosion affiliated with zinc metal anodes, thereby highlighting the necessity for researching conversion anode materials as a promising pathway forward. Copper sulfide (CuS) has been demonstrated as a promising conversion anode material for ZIBs due to its notable electrochemical performance, while challenges persist regarding the Coulombic interactions between Zn2+ and host anions, coupled with the material’s fundamental conductivity that remains less than fully satisfactory. To address the above issues, we have designed and synthesized a nanostructured composite of cobalt doped CuS integrated in graphene oxide frames (GO/Co-CuS) as anode for ZIBs. The cobalt doping serves to alleviate Coulomb interaction (Coulomb attraction) between Zn2+ and host anions, thereby enhancing the kinetics of Zn2+ diffusion. Furthermore, the incorporation of GO framework improves the electrical conductivity of the material and mitigates volume expansion during the reaction process. The synergistic effect engendered by the combination of cobalt doping and the incorporation of a GO framework results in the remarkable electrochemical performance exhibited by GO/Co-CuS. The GO/Co-CuS composite nanostructure exhibited commendable rate capability and cycling stability. Specifically, it exhibits remarkable rate capability, delivering 296 mAh g−1 at 1 A/g and 168 mAh g−1 at 10 A/g. Furthermore, after 1000 cycles at a high current density of 10 A/g, it maintains a capacity of 166 mAh g−1, demonstrating exceptional cycling stability. Additionally, the full-cell configuration of GO/Co-CuS//MnO2@CNTs, when cycled 241 times at 2 A/g, retains a capacity of 79 mAh g−1, thereby confirming the practical efficacy of the GO/Co-CuS nanocomposite as an efficient conversion anode for ZIBs.

Efficient pathways for photogenerated charge transfer induced by Co dopants in WO3/TiO2 nanorod arrays

Modifying the energy band structure in heterostructured photocatalysts enhances charge separation efficiency and improves photoelectrochemical (PEC) performance by decreasing the charge transfer barrier. In this study, cobalt doping into WO3/TiO2 core/shell heterojunction nanorod arrays introduces versatile valence states of cobalt altering the oxygen coordination environment around W atoms in WO3, resulting in an increase in W5+ ions and oxygen vacancy defects in WO3 lattice, facilitating the water splitting reaction. Photogenerated electrons transfer easily from the WO3:Co shell to the TiO2 core due to the lower conduction band minimum (CBM) of WO3:Co shell. Moreover, photogenerated holes transfer from the TiO2 core to the WO3:Co shell efficiently due to the higher valence band maximum (VBM) of TiO2 core. The heterostructure has a high photogenerated carrier density (9.89 × 1018 cm-3), improving photoconversion efficiency (2.55 mA cm-2 at 1.23 V vs. RHE) and reducing charge recombination rates (6.51 × 10–4 s-1). Co doping increases the -OH bond on WO3/TiO2 surface, improves its hydrophilicity, and is more conducive to the reaction in aqueous electrolyte. Additionally, the nanorod array structure facilitates PEC reaction kinetics by providing open spaces for mass exchange. This work proposes a feasible strategy for improving photogenerated charge transport and enhancing PEC by combining regulation of the band structure of WO3/TiO2 heterostructures with morphology design.

Ru doping triggering reconstruction of cobalt phosphide for coupling glycerol electrooxidation with seawater electrolysis

Seawater electrolysis is a promising approach for sustainable energy without relying on precious freshwater. However, the large-scale seawater electrolysis is hindered by low catalytic efficiency and severe anode corrosion caused by the harmful chlorine. In contrast to the oxygen evolution reaction (OER) and chlorin ion oxidation reaction (ClOR), glycerol oxidation reaction (GOR) is more thermodynamically and kinetically favorable alternative. Herein, a Ru doping cobalt phosphide (Ru-CoP2) is proposed as a robust bifunctional electrocatalyst for seawater electrolysis and GOR, for the concurrent productions of hydrogen and value-added formate. The in situ and ex situ characterization analyses demonstrated that Ru doping featured in the dynamic reconstruction process from Ru-CoP2 to Ru-CoOOH, accounting for the superior GOR performance. Further coupling GOR with hydrogen evolution was realized by employing Ru-CoP2 as both anode and cathode, requiring only a low voltage of 1.43 V at 100 mA cm−2, which was 250 mV lower than that in alkaline seawater. This work guides the design of bifunctional electrocatalysts for energy-efficient seawater electrolysis coupled with biomass resource upcycling.

Synthesis of TiO2 Thin Film with Cobalt Doping Using Sol-Gel Spin-Coating Technique as a Solar Cell Material

Research has been done on thin films by mixing TiO2 with cobalt doping and adding HCI as a solar cell material. The aim of this research is to produce a thin layer that is good for use in solar cells. This research has several stages, namely: 1) weighing cobalt and titanium; 2) glass substrate preparation; 3) making a sol-gel solution; 4) thin layer deposition; and 5) heating the sample. From these several stages, the result was that a pure TiO2 solution without doping obtained a thick white solution, whereas the more doping used, the fainter the color of the solution obtained. The thin-layer synthesis process uses a spin-coating method assisted by a modified centrifuge to evenly distribute the sol-gel solution on the surface of the glass substrate

Suppressing Surface Oxidation of Pyrite FeS2 by Cobalt Doping in Lithium Sulfur Batteries.

Lithium-sulfur batteries have emerged as a promising energy storage device due to ultra-high theoretical capacity, but the slow kinetics of sulfur and polysulfide shuttle hinder the batteries' further development. Here, the 10% cobalt-doped pyrite iron disulfide electrocatalyst deposited on acetylene black as a separator coating in lithium-sulfur batteries is reported. The adsorption rate to the intermediate Li2S6 is significantly improved while surface oxidation of FeS2 is inhibited: iron oxide and sulfate, thus avoiding FeS2 electrocatalyst deactivation. The electrocatalytic activity has been evaluated in terms of electronic resistivity, lithium-ion diffusion, liquid-liquid, and liquid-solid conversion kinetics. The coin batteries exhibit ultra-long cycle life at 1C with an initial capacity of 854.7 mAh g-1 and maintained at 440.8 mAh g-1 after 920 cycles. Furthermore, the separator is applied to a laminated pouch battery with a sulfur mass of 326 mg (3.7 mg cm-2) and retained the capacity of 590 mAh g-1 at 0.1 C after 50 cycles. This work demonstrates that FeS2 electrocatalytic activity can be improved when Co-doped FeS2 suppresses surface oxidation and provides a reference for low-cost separator coating design in pouch batteries.

Optimizing NO2 gas sensor performance: Investigating the influence of cobalt doping on WO3 recovery kinetics for enhanced gas sensing application

Gas sensors utilizing a chemiresistive metal oxide semiconductor (MOS) are extensively employed, particularly for detecting nitrogen dioxide (NO2) at moderate temperatures. However, the gas response and the recovery time are hindering the performance of the MOS. In this research, to enhance the gas response and the recovery time a systematic investigation was performed to explore the impact of cobalt (Co) doping in tungsten trioxide (WO3) and its gas sensing properties. Fascinatingly, the 3 mM% Co-doped WO3 sensor exhibits a remarkable gas sensing response of 20776 % at 10 ppm NO2, showcasing a seven-fold enhancement compared to the pristine WO3 sample at 200 ℃. The findings demonstrated that the sensor exhibited an outstanding repeatability, selectivity and long-term stability of 95 % over 8 weeks. Moreover, the sensor possessed a fast response and recovery time 15 s/23 s as compared to the pristine sensor 26 s/154 s. The exceptional gas-sensing capabilities can be ascribed to the existence of defects (oxygen vacancy) within the structure. These defects effectively boost the surface reactivity of WO3 nanoplates, thereby augmenting their sensitivity and enabling a broad-range sensing performance. As a result, this research demonstrates considerable promise for utilizing environmental NO2 monitoring applications.

Semisynthetic ferritin-based nanoparticles with high magnetic anisotropy for spatial magnetic manipulation and inductive heating.

The human iron storage protein ferritin represents an appealing template to obtain a semisynthetic magnetic nanoparticle (MNP) for spatial manipulation or inductive heating applications on a nanoscale. Ferritin consists of a protein cage of well-defined size (12 nm), which is genetically modifiable and biocompatible, and into which a magnetic core is synthesised. Here, we probed the magnetic response and hence the MNP's suitability for (bio-)nanotechnological or nanomedical applications when the core is doped with 7% cobalt or 7% zinc in comparison with the undoped iron oxide MNP. The samples exhibit almost identical core and hydrodynamic sizes, along with their tunable magnetic core characteristics as verified by structural and magnetic characterisation. Cobalt doping significantly increased the MNP's anisotropy and hence the heating power in comparison with other magnetic cores with potential application as a mild heat mediator. Spatial magnetic manipulation was performed with MNPs inside droplets, the cell cytoplasm, or the cell nucleus, where the MNP surface conjugation with mEGFP and poly(ethylene glycol) gave rise to excellent intracellular stability and traceability within the complex biological environment. A magnetic stimulus (smaller than fN forces) results in the quick and reversible redistribution of the MNPs. The obtained data suggest that semisynthetic ferritin MNPs are highly versatile nanoagents and promising candidates for theranostic or (bio-)nanotechnological applications.