Co3O4 Phase Research Articles

Impact of ultrasonic treatment duration on the microstructure and electrochemical performance of NiZnCo2O4 electrode materials for supercapacitors

This work investigates the impact of different ultrasonic treatment durations on the synthesis and electrochemical performance of NiZnCo2O4 (NZC) supercapacitor electrodes. Optimizing treatment to 20 min resulted in a uniform, compact NiZnCo2O4 layer with improved nanostructures, which increased the surface area and active sites for electrochemical reactions. X-ray diffraction (XRD) confirmed successful NiZnCo2O4 synthesis, revealing distinct crystalline phases of NiO, ZnCo2O4, and Co3O4, with improved crystallinity. Electrochemical tests, conducted using a 1.0 M KOH electrolyte, demonstrated that the NZC-2 electrode treated for 20 min achieved the highest 5.678 F/cm3 volumetric capacitance at 0.5 mA/cm2 current density along with 70.5 Wh/kg an energy density at 260 W/kg power density. The galvanostatic charge-discharge and cyclic voltammetry tests revealed that NZC-2 maintained superior charge-discharge efficiency, showing the longest discharge time at 1 mA/cm². Electrochemical impedance spectroscopy (EIS) measurements demonstrated that NZC-2 exhibited the lowest total impedance, thereby enhancing ion transport efficiency. The NZC-2/AC asymmetric supercapacitor showed excellent long-term stability, retaining 64.2% of its capacity after 20,000 charge-discharge cycles. It successfully powered a 1.2 V small fan, demonstrating its practical applicability. The results highlight the crucial importance of ultrasonic treatment in greatly improving the structural and electrochemical characteristics of NiZnCo2O4 electrodes, which opens up possibilities for the advancement of high-performance supercapacitors.

Effect of laser heating on partial decomposition of ZnCo2O4 nanoparticles: Raman study

We conducted a comprehensive investigation into the nanostructuring of the ZnO/CoO mixture by laser heating and optical attributes of partial decomposition of the obtained two-phase system represented by ZnO and ZnCo2O4. Starting mixtures were obtained across a broad range of dopant, CoO, concentrations, spanning from 5 % to 90 % of CoO. The samples were methodically prepared using the coprecipitation method and subjected to calcination at 600 °C. Laser-induced heating experiments were conducted at nine distinct laser powers. The characterization of these samples was accomplished through the utilization of SEM, XRD, and Raman spectroscopy. XRD analysis unveiled the presence of ZnO and ZnCo2O4 phases. Concurrently, we systematically monitored nanostructuring effects caused by laser-induced heating, the influence of partial decomposition on the behavior of surface optical phonons (SOP), and phase transitions in the samples with varying dopant concentrations during the performed experiment. New phases, including Zn1-xCoxO, ZnyCo3-yO4, CoO, and even the Co3O4 phase, were unveiled. The Raman spectra obtained distinctly indicate the presence of surface optical phonons (SOP), emphasizing the existence of the ZnO phase. The alterations in the behavior of surface optical phonon (SOP) modes were meticulously examined by laser-induced heating nanostructuring effects where it became evident that there was a discernible loss of these modes with an increase in dopant concentration and laser power. This detailed study sheds light on the intricate interplay between dopant concentration, laser power nanostructuring, partial decomposition, and the evolution of phase transformations and surface optical phonon modes in the examined samples.

Investigation of the Influence of the Oxygen Flow Rate on the Mechanical, Structural and Operational Properties of 86WC-10Co-4Cr Coatings, as Determined Using the High-Velocity Oxyfuel Spraying Method

The structural-phase composition and tribological and performance properties of coatings based on an 86WC-10Co-4Cr composition obtained by the HVOF method at varying (150 L/min, 170 L/min, 190 L/min) oxygen flow rates were studied. The results showed that the coefficient of friction of coatings in gear oil remained almost unchanged with the variation in oxygen flow rate. However, microhardness increased significantly with an increasing oxygen flow rate, reaching a maximum at 190 L/min. An increasing oxygen flow rate was also accompanied by an increase in roughness and coating thickness, with a decrease in porosity, particularly notable at 190 L/min. Adhesion strength reached the maximum values for the A2 and A3 coatings under high loads. The phase composition of the coatings included WC, W2C and CoO phases irrespective of the oxygen flow rate, and their microstructure was characterized by a more homogeneous and dense structure. Thus, this study confirmed that the optimal oxygen flow rate for achieving an improved performance and tribological characteristics of 86WC-10Co-4Cr coatings is 190 L/min.

Synthesis of Au/Co3O4/PVA hybrid nanocomposites via eco-friendly method based on pulsed laser ablation process for water treatment

A portable nanostructured nanocomposite film, based on cobalt oxide and gold nanoparticles (NPs) embedded in a polyvinyl alcohol structure (PVA), Au/Co3O4/PVA, was prepared via a novel way based on pulsed laser ablation to be applied as an effective catalytic degradation material for a hazardous chemical structure as nitro compounds. Au/Co3O4/PVA was investigated by the techniques of UV–Vis, FT-IR, SEM, and XRD. From XRD, the decrease in crystallinity of PVA is attributed to the intermolecular hydrogen bonding between PVA and Au/Co3O4. In addition, there are five interplanar peaks, with three shared peaks by both phases and one unique peak for each phase of Au and Co3O4. From FT-IR, the modes observed at a 500–1200 cm-1 wavenumber range correspond to the stretching vibration modes of Au/Co3O4. From UV–VIS, as the embedding of Co3O4 on Au-PVA structure increases, the energy band gap is shifted to a lower value. This is due to the embedding of Co3O4 NPs. From SEM, in the case of embedding PVA with Au NPs, the bright semi-spherical shape of the nanostructured materials has a bright semi-spherical light area. Moreover, in the case of the embedded PVA with Co3O4 NPs, the faint semi-spherical form of the nanostructured materials is discernible. Besides, the catalytic activity performance is tested for the degradation of 4-nitrophenol, which reveales that the reaction followed first-order kinetics, as indicated by linear regression analysis. The results shows that the sample completely convertes 4-nitrophenol to 4-aminophenol within 6 min.

Impact of pH Preparation on the Physical Nature and Metal Phase of Zeolite-Supported Metal Catalyst

The synthesis of CoMo/USY catalysts has been widely carried out. However, the bond strength between metal and USY is still a problem. Therefore, this research has synthesised the catalyst with the chelating agent ethylenediaminetetraacetate (EDTA). Apart from that, the effect of pH on the characteristics of the catalyst is also reviewed. This research aims to analyse the effect of preparation pH on catalyst characteristics. In the preparation process, the pH of the solution is set at values of 2, 7, and 8. Catalyst activation includes a calcination process and reduction. The catalyst characterisation uses XRD, GSA, and FTIR instruments to determine phase composition, specific surface area, and functional groups. The result showed that pH preparation significantly influenced the metal loading on the catalyst and reached a maximum at pH 8. The surface area is not directly related to the pH of the preparation but has the opposite property depending on the amount of metal added. Meanwhile, it was found that the CoO and MoO3 phases were achieved on the catalyst by all pH preparations. On the other hand, the CoMo alloys are present on the catalyst at pH 7 and 8, while the Co and Mo elements are visible at pH 2. The difference in pH during the synthesis process impacts the shift in the absorption wave number of the OH vibration.

Broadband dielectric spectroscopy studies of Co3O4 and Co2TiO4 two-phase spinel composites

Broadband dielectric spectroscopy studies of the two-phase composites, (1 – x) Co3O4 + x Co2TiO4, have been reported over a wide range of compositions (0 ≤ x ≤ 1) and temperatures (80 K ≤ T ≤ 573 K). Normal spinel Co3O4 and inverse spinel Co2TiO4 phases are well distinguishable with ∼4.6 % variation in the lattice parameter of the Co3O4 phase with an increase of x from 0 to x = 1. The ac-conductivity (σ) of this composite follows Johnscher's power law (∼Aωs) variation with frequency exponent factor ‘s’ both greater than as well as less than unity. The temperature dependence of ‘σ’ reveals the Arrhenius-like behavior instead of variable range hopping of charge carriers with activation energy in the 2–1800 meV range. Systematic analysis of such conductivity mechanisms for all the compositions is compared with the pristine Co3O4 system.

Simplified synthesis and identification of novel nanostructures consisting of cobalt borate and cobalt oxide for crystal violet dye removal from aquatic environments

Crystal violet dye poses significant health risks to humans, including carcinogenic and mutagenic effects, as well as environmental hazards due to its persistence and toxicity in aquatic ecosystems. This study focuses on the efficient removal of crystal violet dye from aqueous media using novel Co3O4/Co3(BO3)2 nanostructures synthesized via the Pechini sol–gel approach. The nanostructures, which were abbreviated to EN600 and EN800, were fabricated at calcination temperatures of 600 and 800 °C, respectively. X-ray diffraction (XRD) analysis revealed that the synthesized samples have a cubic Co3O4 phase and an orthorhombic Co3(BO3)2 phase, with mean crystal sizes of 43.82 nm and 52.93 nm for EN600 and EN800 samples, respectively. The Brunauer–Emmett–Teller (BET) surface areas of EN600 and EN800 samples were 65.80 and 43.76 m2/g, respectively, indicating a significant surface area available for adsorption. Optimal removal of crystal violet dye was achieved at a temperature of 298 K, a contact time of 70 min, and a pH of 10. The maximum adsorption capacities were found to be 284.09 mg/g for EN600 and 256.41 mg/g for EN800, which are notably higher compared to many conventional adsorbents. The adsorption process followed the pseudo-second-order kinetic model and fitted well with the Langmuir isotherm. The adsorption was exothermic, spontaneous, and physical in nature. Moreover, the adsorbents exhibited excellent reusability, retaining high efficiency after multiple regeneration cycles using 6 mol/L hydrochloric acid. These findings highlight the potential of these Co3O4/Co3(BO3)2 nanostructures as effective and sustainable materials for water purification applications.

Hierarchical mesoporous Co3O4@C-N nanostructure rods derived from a metal-organic framework as high-performance anode for lithium-ion battery

A uniform hierarchical mesoporous Co3O4@C-N nanostructure rods were in situ fabricated successfully by developing a facile one-step strategy. Cobalt-based metal organic framework [Co3(ndc)(HCOO)3(μ-OH)(H2O)]n with special Co chine constructed framework structure treated as a precursor directly pyrolyzed in a mixed atmosphere of argon and oxygen (95:5) at 500 °C for 2 h. According to the XRD pattern, SEM, TEM, EDS mapping images and XPS spectrum analysis, the well-defined hierarchical mesoporous Co3O4@C-N nanostructure rods showed pure Co3O4 phase, are assembled from a large number of core–shell structured Co3O4@C-N spherical particles with an ultrasmall and uniform size (∼8 nm) which were further connected by N doped carbon net to form nanostructure rods. Using as anode material for lithium-ion batteries, these hierarchical mesoporous Co3O4@C-N nanostructure rods exhibit excellent electrochemical performance with high reversible capacity, rate capability and good cycling stability. They maintained a reversible specific capacity of more than 1000 mAh/g at 100 mA/g, and the discharge specific capacities at the 5 current density of 0.1, 0.2, 0.5, 1, 2, and 5 A/g reached 1123, 1094, 1044, 979, 879 and 688 mAh/g, respectively.

Co3O4@SiO2 3D Monolith Catalysts, Additive Manufactured Structures for Propane Oxidation Reaction

AbstractIn this study, we successfully fabricated a three‐dimensional Co3O4@SiO2 3D Monolith catalyst. This process allowed for the effective and straightforward anchoring of Co3O4 nanoparticles onto SiO2 3D Monoliths. The active Co3O4 phase was primarily identified through XRD and XPS analyses, complemented by Co3O4 loading measurements (1.7 %). This innovative catalyst displayed remarkable proficiency in selectively converting propane to carbon dioxide. Additionally, it was demonstrated that the catalytic activity remained unimpaired even upon the catalyst's reuse in 5 successive reaction cycles. This performance was observed across various heating ramps, showcasing the catalyst's stability over time.

3D-Printed Hierarchically Microgrid Frameworks of Sodiophilic Co3O4@C/rGO Nanosheets for Ultralong Cyclic Sodium Metal Batteries.

Herein, hierarchically structured microgrid frameworks of Co3O4 and carbon composite deposited on reduced graphene oxide (Co3O4@C/rGO) are demonstrated through the three-dimensioinal (3D)printing method, where the porous structure is controllable and the height and width are scalable, for dendrite-free Na metal deposition. The sodiophilicity, facile Na metal deposition kinetics, and NaF-rich solid electrolyte interphase (SEI) formation of cubic Co3O4 phase are confirmed by combined spectroscopic and computational analyses. Moreover, the uniform and reversible Na plating/stripping process on 3D-printed Co3O4@C/rGO host is monitored in real time using in situ transmission electron and optical microscopies. In symmetric cells, the 3D printed Co3O4@C/rGO electrode achieves a long-term stability over 3950 at 1mA cm-2 and 1 mAh cm-2 with a superior Coulombic efficiency (CE) of 99.87% as well as 120h even at 20mA cm-2 and 20 mAh cm-2, far exceeding the previously reported carbon-based hosts for Na metal anodes. Consequently, the full cells of 3D-printed Na@Co3O4@C/rGO anode with 3D-printed Na3V2(PO4)3@C-rGO cathode (≈15.7mg cm-2) deliver the high specific capacity of 97.97 mAh g-1 after 500 cycles with a high CE of 99.89% at 0.5 C, demonstrating the real operation of flexible Na metal batteries.

Stabilizing magnetic order of cobalt-based anisotropic nanoparticles prepared using NaBH4 as a reducing agent

A one-pot chemical method was used to prepare cobalt nanoparticles (Co NPs) by employing sodium borohydride (NaBH4) as a reducing agent, as well as graphite and activated carbon as stabilizer materials. The resulting NPs were characterized by XRD, FE-SEM, EDX mapping and VSM measurements before and after annealing under a mixture of argon and hydrogen atmosphere at 600 ℃, in order to study their structural, morphological, and magnetic properties. This study focused on the shape and size of Co NPs, involving the formation of Co and Co3O4 phases with the effect of oxygen as the main factor that can significantly contribute to the magnetic anisotropy. Co NPs exhibited a high saturation magnetization (Ms) value after performing the annealing process, achieving Ms> 99 emu/g when using the graphite stabilizer. The results indicate that surface atoms play a significant role in the modification of magnetic characteristics of Co NPs.

Nanoengineered Cobalt Electrocatalyst for Alkaline Oxygen Evolution Reaction.

The alkaline oxygen evolution reaction (OER) remains a bottleneck in green hydrogen production owing to its slow reaction kinetics and low catalytic efficiencies of earth abundant electrocatalysts in the alkaline OER reaction. This study investigates the OER performance of hierarchically porous cobalt electrocatalysts synthesized using the dynamic hydrogen bubble templating (DHBT) method. Characterization studies revealed that electrocatalysts synthesized under optimized conditions using the DHBT method consisted of cobalt nanosheets, and hierarchical porosity with macropores distributed in a honeycomb network and mesopores distributed between cobalt nanosheets. Moreover, X-ray photoelectron spectroscopy studies revealed the presence of Co(OH)2 as the predominant surface cobalt species while Raman studies revealed the presence of the cubic Co3O4 phase in the synthesized electrocatalysts. The best performing electrocatalyst required only 360 mV of overpotential to initiate a current density of 10 mA cm-2, exhibited a Tafel slope of 37 mV dec-1, and stable OER activity over 24 h. The DHBT method offers a facile, low cost and rapid synthesis approach for preparation for highly efficient cobalt electrocatalysts.

Investigation of the Influence of Powder Fraction on Tribological and Corrosion Characteristics of 86WC-10Co-4Cr Coating Obtained by HVOF Method

Samples using powders of four different fractions, 15–20 μm, 20–30 μm, 30–40 μm and 40–45 μm, were fabricated to investigate the wear resistance, corrosion resistance and tribological properties of the 86WC-10Co-4Cr coating obtained using the HVOF method. The phase composition, microstructure and elemental distribution were analyzed using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. The hardness was measured on a Vickers microhardness tester, the friction coefficient and wear rate were investigated using a tribometer, and the corrosion resistance was evaluated on an electrochemical corrosion station. The results showed that the cross-sectional microstructure of the coating is mainly represented by multifaceted WC crystals embedded in the Co-Cr matrix and the presence of lower tungsten carbides, particularly W2C. The 15–20 μm fraction particles were subjected to superheating, contributing to the decarburization process. The 20–30 µm and 30–40 µm sized particles prevented overheating and had a more homogeneous structure. The 40–45 µm powder fractions did not reach sufficient temperature for complete melting, resulting in the formation of pores in the coating layers. The phase composition of the coatings included WC, W2C and CoO phases. According to the results of the study, it was found that the optimal powder fraction for coating the 86WC-10Co-4Cr composition with improved characteristics is the fraction of the 20–30 µm sized particles.

Synthesis and characterization of Co3O4 spinel nanowall: understanding the growth mechanism and properties

Formation of spinel tricobalt tetraoxide (Co3O4) nanostructures through a controlled thermal oxidation process is discussed here. Thin films of high purity cobalt (Co) were deposited on glass/quartz substrates using an electron beam (E-beam) evaporation technique. Thermal oxidation of the as-deposited Co thin films was carried out at various oxidation temperatures (400 °C to 600 °C) for different durations (5 h to 15 h) to grow various oxide nanostructures. Different surface characterizations techniques were used to investigate the structure, chemistry and electronic properties of the as-grown cobalt oxide nanostructures. x-ray diffraction analysis revealed the presence of the CoO phase along with the Co3O4 phases at relatively lower oxidation temperature. However, the Co3O4 phase becomes more predominant for longer oxidation durations at higher oxidation temperatures. Field emission scanning electron microscopy analysis showed a surface morphological transition from nanowalls to nanograins with an increase in the oxidation temperature. The surface electrical conductivity of the oxidized Co films is also increased for higher oxidation temperature and/or duration mainly due to the oxide phase purity and larger particle sizes. Ultraviolet–visible spectroscopy indicated two distinct optical energy bandgaps, which effectively decreased with an increase in the oxidation temperature and duration. Raman spectroscopy identified five different Raman-active modes corresponding to the Co3O4 phase, with the F2g mode dominating at higher temperatures. All these findings provide clear insights into the structural, electrical, chemical and optical properties of cobalt oxide thin films. Moreover, it provides a mechanism on how to grow 2D nanowalls morphology of Co3O4 films which can further be used in energy, sensor or catalytic applications.

Ceria-Terbium-based electrospun nanofiber catalysts for soot oxidation activity and its kinetics

BackgroundCeria-based materials have an excellent potential to be catalysts for catalytic three-way converters in the automobile industry. Developing Ceria-based nanofiber catalysts can be a significant approach for further exploring the application of these materials in automobile industries. MethodsIn this study, Ag, Cu, or Co doped Ceria–Terbium nanofibers were synthesized using the electrospinning technique. The obtained nanofiber catalysts were characterized using FE-SEM, XRD, FT-Raman Spectroscopy, and BET-BJH analysis and tested for soot oxidation activity and its kinetics. Significant findingsFE-SEM examination reveals that the obtained nanofibers have a diameter ranging from around 100 to 600 nm. CeTbCo nanofibers exhibited a reduced particle size and enhanced pore formation. The XRD investigation revealed that all the nanofibers displayed a face-centered fluorite structure of CeO2. In Raman spectroscopy analysis, CeTbCo nanofibes showed the emergence of a secondary Co3O4 phase. The CeTbCo nanofiber catalyst showed better SBET (specific surface area) (66 m2/g) and average pore size (12.08 nm) and total pore volume (0.223 cc/g)), better soot oxidation activity (T50 = 347 ℃) than other nanofiber catalysts. The CeTbCo nanofiber catalyst exhibited an activation energy of 132 kJ mol−1 and a pre-exponential factor (ln (A)) of 25.63 min−1.

Enhancing electrical and optical properties in layered NaxCoO2 through sodium non-stoichiometry: Insights into surface band bending and oxygen vacancies

The concentration of sodium ions (Na+) in layered sodium cobaltite (NaxCoO2) is a pivotal determinant influencing its physical and chemical properties. This study focused on NaxCoO2 with varying sodium content (x = 1, 0.9, 0.7, 0.5, 0.3, 0.1) to establish a correlation between the sodium concentration and the substantial modulation of the structural and electrical properties. X-ray diffraction and Raman studies confirmed the formation of hexagonal structured NaxCoO2 prepared by the sol-gel method, while a reduction in Na content increased the percentage of the Co3O4 phase. Notably, as the Na content was lowered, the Raman peak shifted towards a lower wavenumber due to the lattice alignment along the c-axis of the crystal plane. Morphological analysis displayed the growth of distinct plate-like structures, with a thickness ranging from 10 to 15 μm, which gradually decreased on lowering Na content. X-ray photoelectron spectroscopy studies revealed an increase in the relative concentration of Co4+/Co3+ with a decrease in sodium content implying a lattice distortion in CoO6 octahedra which led to the creation of additional oxygen vacancies in Na0.7CoO2 (NCO7). Optical studies highlighted a band bending phenomenon in the NCO7, while photoluminescence studies indicated an increase in emission intensity, suggesting the presence of oxygen vacancies in NCO7. Electrical measurements demonstrated the highest conductivity for NCO7 emphasizing the significance of the optimal lattice distortion, generation of oxygen vacancies, and surface band bending effect for efficient charge carrier transportation. This study highlights the crucial role of the sodium ion content between the CoO2 layers in precise tuning of the structural, electronic structure/distortion, optical, and electrical properties of NaxCoO2. The insights gained particularly in optimizing the optical and electrical properties through sodium non-stoichiometry, may hold significant implications for diverse energy conversion and storage devices, catalysis, and even optoelectronics devices.

Enhanced Cathode Performance: The Heterostructure Construction of LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12.

In this study, the heterostructure cathode material LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12 was prepared by coating Li6.4La3Zr1.4Ta0.6O12 on the surface of LiCoO2 through a one-step solid-phase synthesis. The morphology, structure, electrical state, and elemental contents of both pristine and modified materials were assessed through a range of characterization techniques. Theoretical calculations revealed that the LCO@LLZTO material possessed a reduced diffusion barrier compared to LiCoO2, thereby facilitating the movement of Li ions. Electrochemical tests indicated that the capacity retention rate of the modified cathode composites stood at 70.43% following 300 cycles at a 2C rate. This high rate occurred because the Li6.4La3Zr1.4Ta0.6O12 film on the surface enhanced the migration of Li+, and the spinel phase of Co3O4 had better interfacial stability to alleviate the generation of microcracks by inhibiting the phase change from the layered phase to the rock-salt phase, which considerably improved the electrochemical properties.

Construction of Petal‐Like CoO/CoP Heterostructures by Oxygen Vacancy Induced P‐doping for Efficient Overall Water Splitting

AbstractHydrogen energy has become a green, high‐efficiency new energy source due to its superior characteristics. Overall water splitting is considered as an effective method for hydrogen production. However, the synthesis of non‐noble metal‐based robust bi‐functional electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are still challenging. Here, the synthesis of petal‐like CoO/CoP heterostructures is reported by an oxygen vacancy induced P‐doping strategy. The oxygen defect sites of the defective Co3O4–x easily attract phosphorus atoms to enhance the P‐doping process, which induces the formation of a two‐dimensional CoO/CoP heterojunction structure. Due to the synergistic effect between CoP and CoO phases in the catalyst, the heterostructures can well drive the hydrogen and oxygen evolution reactions under alkaline conditions, and thus substantially promotes overall water splitting with a relatively low potential 1.64 V at 10 mA cm−2 without decay even after the durability test for 24 h.

Electrocatalytic ammonia production from nitrite via dual-site Co3O4/NiO catalysts derived from laser-induced cyanonickelate frameworks

Herein, we report the pioneering synthesis of the cobalt–nickel coordination frameworks (Co(H2O)2·Ni(CN)4, CoNi-CF) via pulsed laser irradiation in liquids (PLIL). The distinctive morphology of CoNi-CF has attracted considerable attention as a potential template to produce Co3O4/NiO composites with varying Co and Ni ratios. After subjecting CoNi-CF to a high-temperature calcination process at 400 °C, the resulting Co3O4/NiO composites displayed dual-active canters for efficient electrochemical nitrite (NO2−) reduction to ammonia (NH3). Optimizing the Co:Ni ratio at 1:0.75 yielded Co3O4/NiO with exceptional performance, achieving a remarkable 99.4 % Faradaic efficiency in NH3 production while maintaining a 96.1 % mass balance at −1.2 V vs. Ag/AgCl. Furthermore, this composite displayed long-term stability, degrading 60.82 % of NO2− in 180 min, with high NH3 yield rate (2012.03 μM h−1 cm−2) at −1.6 V vs. Ag/AgCl. The superior performance in NO2− reduction to NH3 can be attributed to the unique structural features inherited from CoNi-CF, including well-defined and self-standing Co3O4 and NiO phases. Synergistic effects at the oxide interface enhance electrochemical performance and facilitate efficient charge transfer kinetics of Co3O4/NiO, underscoring the unique potential of these composite materials.

A Hybrid Synthesis Approach: Tailoring Photocatalytic Activity of Co3O4 Nanoparticles by PEG Functionalization

This study presents a novel fusion of precipitation and hydrothermal methods for the synthesis of polyethylene glycol (PEG)-functionalized cobalt oxide (Co3O4) nanoparticles. The synthesized PEG/Co3O4 nanoparticles characterized using various techniques to elucidate their structure, composition, properties and application. The XRD analysis confirmed the formation of cubic phase of Co3O4 with a crystallite size of 2.04 nm. Two direct bandgap (Eg) transitions were observed at energy levels of 1.68 and 2.5 eV, exhibiting intensities that exceeded those reported in prior studies. The synthesized nanoparticles exhibited distinct structural features as revealed by FESEM and HRTEM investigations. Furthermore, the FTIR analysis provided evidence of interactions between PEG and Co3O4, suggesting successful functionalization. The high crystallinity of the PEG-mediated Co3O4 nanoparticles was further confirmed by the selected area electron diffraction (SAED) pattern. The XPS analysis revealed the presence of Co2+ and Co3+ ions, along with defect sites, confirming the successful synthesis of Co3O4 NPs with controlled oxidation states. These findings offer valuable insights into the chemical composition and electronic structure of the synthesized PEG-mediated Co3O4 nanoparticles. The photocatalytic activity of the PEG/Co3O4 nanoparticles was evaluated through the degradation of Congo red dye, a typical azo dye pollutant. The study revealed that PEG/Co3O4 (dose 200 mg L-1) acted as an efficient photocatalyst for Congo red degradation. These results suggest that PEG-mediated Co3O4 nanoparticles hold promising potential as efficient photocatalysts for the treatment of wastewater containing organic contaminants.