Structure Of Co3O4 Research Articles

Interface Manipulation of Composite Solid Polymer Electrolyte with Polydopamine to Construct Durable and Fast Li+ Conduction Pathways

Taking advantage of light weight, flexibility, and flame retardancy, solid polymer electrolytes (SPEs) provide a feasible solution to these safety concerns and to the enhancement of energy density for lithium-ion batteries (LIBs). However, the development of SPEs is still restricted by low ionic conductivity. Herein, we develop a type of SPE filler built by flower-like Co3O4 microspheres as a lithiophilic backbone and polydopamine (PDA) as a multifunctional coating for the engineering of the interphase properties of the polyether-based SPEs. The hierarchical structure of Co3O4 affords large interfacial contact area with SPEs and effectively suppresses the regular crystallinity of poly(ethylene oxide) (PEO) segments. Moreover, the PDA coating layers with diverse surface functionalities serve as a versatile mediator to finely tune ionic distribution and transport behavior via multiple Lewis acid–base interactions. We uncover the interphase characterizations and their synergistic effects to enhance Li+ conductivity and mechanical/electrochemical stability. This study provides intriguing alternatives for developing composite solid polymer electrolytes (CPEs), for which we further demonstrate the potential application of Co3O4@PDA-based CPEs in all-solid-state LIBs.

Optimizing the electronic structure of Fe-doped Co3O4 supported Ru catalyst via metal-support interaction boosting oxygen evolution reaction and hydrogen evolution reaction

Metal-support interaction (MSI) is an efficient way in heterogeneous catalysis and electrocatalysis to modulate the electronic structure of metal for enhanced catalytic activity. However, there are still great challenges in promoting the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) simultaneously by this way. Herein, Fe-doped Co3O4 supported Ru (Ru/FeCo) catalysts are synthesized by MSI strategies to further improve the electrocatalytic activity and stability of the catalysts. The results show that the optimized Ru/FeCo catalyst exhibits the best catalytic performance. The HER and OER tests at 10 mA/cm2 in 1 mol/L KOH solution show excellent overpotentials of 155 mV and 283 mV, respectively. The activity and stability enhancement can be attributed to the MSI that effectively modify the electronic structure and improve interfacial electron transfer between Ru and Fe-doped Co3O4 (FeCo). This work provides an innovative direction for the design of high-efficiency bifunctional electrocatalysts by virtue of the MSI.

Facile Synthesis of MOF-Derived Hierarchical Flower-Like Sr-Doped Co3O4 Structure for Effective TEA Sensing

Metal-organic framework (MOF)-derived metal oxide semiconductors (MOSs) have drawn great attention because of their abundant pore structures, large surface area, and good gas accessibility. Herein, hierarchical flower-like Sr-doped cobalt oxide (Co3O4) structure is obtained utilizing MOF as a self-sacrificing template. Compared with undoped Co3O4, the 2 mol% Sr-doped Co3O4 shows better triethylamine (TEA) sensing performance. It exhibits not only high response values of 52 (the response of undoped Co3O4 are about 3.3) and short response/recovery time (40/58 s) to 100 ppm TEA at a low working temperature of 160 °C, but also excellent selectivity and long-term stability, which show that the as-obtained flower-like Sr-doped Co3O4 structure is an effective material to detect TEA gas. The enhanced sensing properties are attributed to the synergistic effect of the creation of more oxygen vacancies and larger surface area of flower-like structure.

Modulating the electron structure of Co-3d in Co3O4−x/WO2.72 for boosting peroxymonosulfate activation and degradation of sulfamerazine: Roles of high-valence W and rich oxygen vacancies

Sulfate radical (SO4•–)-based heterogonous advanced oxidation processes (AOPs) show promising potential to degrade emerging contaminants, however, regulating the electron structure of a catalyst to promote its catalytic activity is challenging. Herein, a hybrid that consists of Co3O4−x nanocrystals decorated on urchin-like WO2.72 (Co3O4−x/WO2.72) with high-valence W and rich oxygen vacancies (OVs) used to modulate the electronic structure of Co-3d was prepared. The Co3O4−x/WO2.72 that developed exhibited high catalytic activity, activating peroxymonosulfate (PMS), and degrading sulfamerazine (SMR). With the use of Co3O4−x/WO2.72, 100 % degradation of SMR was achieved within 2 min, at a pH of 7, with the reaction rate constant k1 = 3.09 min−1. Both characterizations and density functional theory (DFT) calculations confirmed the formation of OVs and the promotion of catalytic activity. The introduction of WO2.72 greatly regulated the electronic structure of Co3O4−x. Specifically, the introduction of high-valence W enabled the Co-3d band centre to be closer to the Fermi level and enhanced electrons (e–) transfer ability, while the introduction of OVs-Co in Co3O4−x promoted the activity of electrons in the Co-3d orbital and the subsequent catalytic reaction. The reactive oxygen species (ROS) were identified as •OH, SO4•–, and singlet oxygen (1O2) by quenching experiments and electron spin resonance (EPR) analysis. The DFT calculation using the Fukui index indicated the reactive sites in SMR were available for an electrophilic attack, and three degradation pathways were proposed.

Co3O4 Nanowires Decorated with BOx Species for Electrocatalytic Oxygen Evolution

One-dimensional nanowires possess significant advantages in active site exposure and electron and matter transport. Their oxygen evolution reaction (OER) performances can be well enhanced by the introduction of oxygen vacancies (Ov) and boron element (B), which, however, have not been achieved simultaneously. Herein, the Ov and BOx motifs were simultaneously employed in typical cobalt spinel oxide nanowires via simple NaBH4 hydrolysis (Co3O4/BOx). When grown on carbon fiber cloth, the observed Co3O4/BOx nanowire array electrode drives a current density of 10 mA cm–2 with only 328 mV overpotential in a 1.0 M KOH solution, which is much superior to the spinel Co3O4. We found that the BOx motifs and Ov have efficiently tuned electronic structures of Co3O4, thereby enhancing the electrical conductivity and generating a large number of electroactive sites. This study provides a simple solution for designing and producing nanostructure OER catalysts with excellent electrochemical performance.

Enhanced structural, optical, and photo sensing properties of Ni-doped Co3O4 thin films prepared by nebulizer spray pyrolysis method

In the current manuscript, we deal with pure and 2, 4, 6, 8, and 10 wt% Ni-doped Co3O4 thin films prepared using the Nebulizer spray pyrolysis method. An in-depth discussion is provided on improving crystalline, morphological, optical, electrical, and photodetection characteristics of pure and Ni-doped samples. The cubic spinel structure of Co3O4 has been established by the X-ray diffraction (XRD) study. Microscopy studies using Field Emission Scanning Electron (FESEM) technology reveal tiny grains aggregated together that are in qualitative accord with the crystalline sizes determined by XRD analysis. Energy dispersive X-ray (EDX) analysis has observed the presence of constituent elements in the prepared films. The results of the photoluminescence (PL) experiments demonstrate the quality of the crystal structure and the presence of defects in the films. According to the absorption measurements, two-band gap values are determined in the range of 1.55 to 1.25 eV and in the range of 2.0 to 2.0 eV for different Ni doping concentrations, respectively. The maximum photoconductive parameters such as photo-responsivity (R), external quantum efficiency (EQE), and detectivity (D*) of 1.64 × 10−1AW−1, 38%, and 9.273 × 108 Jones were achieved for 8% Ni-doped Co3O4 sample. The results obtained in the present study indicate that the 8% Ni-doped Co3O4 sample finds suitable material for photodetector devices.

Trace W-doping flocculent Co3O4 nanostructures with enhanced electrocatalytic performance for methanol oxidation reaction

The electronic structure of electrocatalysts plays a critical role in the design of methanol oxidation reaction (MOR) catalysts. Herein, a series of Co3O4 electrocatalysts with W doping at different levels, including 0, 2.5, and 5% have been prepared by a facile method. According to results of comparisons, 2.5 % W-doped catalyst exhibits low onset potential and high mass activity (377.75 mA mg−1) in alkaline media, which is 1.825 times higher than that of pure Co3O4 at the same conditions. The superior catalytic activity of 2.5 % W-doped Co3O4 for methanol oxidation is attributed to enhanced dispersibility and optimized electronic structure of Co3O4. The activity and stability of catalytic systems prove W-doped Co3O4 catalyst can be a candidate of efficient electrocatalysts towards MOR.

Cu-doped Co3O4 spinel on cordierite monolithic for catalytic oxidation of VOCs

Ultrasonic impregnation was used to load Co3O4 with different amounts of Cu doping on cordierite monoliths. The effect of Cu doping amount on the structure of Co3O4 was investigated in detail. Among the different samples, Co2Cu1 with Co and Cu ratio of 2:1 presented the excellent catalytic activity for 500 ppm toluene (T90 = 210 °C), 500 ppm ethyl acetate (T90 = 170 °C) and 1000 ppm mixture of toluene and ethyl acetate oxidation (T90 = 220 °C), which was attributed to the abundant oxygen vacancies created by the Co3+/Co2+ increase in Co3O4 spinel due to Cu doping. In addition, Co2Cu1 presented a satisfactory cycle, long-term and mechanical stability, water resistance. This work provided a new route for the design of monolithic catalysts in VOCs oxidation.

Solar light induced photocatalytic degradation of tetracycline in the presence of ZnO/NiFe2O4/Co3O4 as a new and highly efficient magnetically separable photocatalyst.

In this study, a new solar light-driven magnetic heterogeneous photocatalyst, denoted as ZnO/NiFe2O4/Co3O4, is successfully prepared. FT-IR, XPS, XRD, VSM, DRS, FESEM, TEM, EDS, elemental mapping, and ICP analysis are accomplished for full characterization of this catalyst. FESEM and TEM analyses of the photocatalyt clearly affirm the formation of a hexagonal structure of ZnO (25–40 nm) and the cubic structure of NiFe2O4 and Co3O4 (10–25 nm). Furthermore, the HRTEM images of the photocatalyst verify some key lattice fringes related to the photocatalyt structure. These data are in very good agreement with XRD analysis results. According to the ICP analysis, the molar ratio of ZnO/NiFe2O4/Co3O4 composite is obtained to be 1:0.75:0.5. Moreover, magnetization measurements reveals that the ZnO/NiFe2O4/Co3O4 has a superparamagnetic behavior with saturation magnetization of 32.38 emu/g. UV-vis DRS analysis indicates that the photocatalyst has a boosted and strong light response. ZnO/NiFe2O4/Co3O4, with band gap energy of about 2.65 eV [estimated according to the Tauc plot of (αhν)2 vs. hν], exhibits strong potential towards the efficacious degradation of tetracycline (TC) by natural solar light. It is supposed that the synergistic optical effects between ZnO, NiFe2O4, and Co3O4 species is responsible for the increased photocatalytic performance of this photocatalyst under the optimal conditions (photocatalyst dosage = 0.02 g L−1, TC concentration = 30 mg L−1, pH = 9, irradiation time = 20 min, and TC degradation efficiency = 98%). The kinetic study of this degradation process is evaluated and it is well-matched with the pseudo-first-order kinetics. Based on the radical quenching tests, it can be perceived that •O2 − species and holes are the major contributors in such a process, whereas the •OH radicals identify to have no major participation. The application of this methodology is implemented in a facile and low-cost photocatalytic approach to easily degrade TC by using a very low amount of the photocatalyst under natural sunlight source in an air atmosphere. The convenient magnetic isolation and reuse of the photocatalyst, and almost complete mineralization of TC (based on TOC analysis), are surveyed too, which further highlights the operational application of the current method. Notably, this method has the preferred performance among the very few methods reported for the photocatalytic degradation of TC under natural sunlight. It is assumed that the achievements of this photocatalytic method have opened an avenue for sustainable environmental remediation of a broad range of contaminants.

High-valance molybdenum doped Co3O4 nanowires: Origin of the superior activity for 5-hydroxymethyl-furfural oxidation

Co3O4 has been widely explored in electrocatalytic 5-hydroxymethyl-furfural (HMF) oxidation. However, the poor intrinsic ability has seriously limited its electrochemical ability. Heteroatom-doping is an efficient method to enhance the electrocatalytic ability of catalyst by regulating electronic structure. Herein, we have modulated the electronic structure of Co3O4 by high valance Mo6+-doping. With the introduction of Mo6+, the content of Co2+ was increased and metal-oxygen bond was strength. Electrochemical results suggested that the electrocatalytic ability of Co3O4 towards HMF oxidation has been dramatically improved and reaction kinetics has been fasten. Theoretical calculations demonstrated that the surrounding cobalt sites after Mo6+-doping with assembled electron has a strong adsorption ability towards HMF molecule leading to more favourable oxidation of HMF. Post characterizations demonstrated pristine Co3O4 structure was kept after electrolysis cycles and CoOOH active species were formed. This work provides a valuable reference for developing efficient heteroatom-doped electrocatalysts for HMF oxidation.

Engineering Co3O4 with Co defects for highly sensitive nonenzymatic detection of glucose

Defect engineering was considered as an effective strategy to regulate electrocatalytic activities of transition metal oxides. However, there are seldom reports about metal defects in electrochemical sensing. In this work, Co-defected Co3O4 was synthesized via thermal treatment of glycerolatocobalt (CoGly) precursor for constructing a novel electrochemical nonenzymatic glucose sensor. The obtained nanomaterials were characterized by transmission electron microscopy (TEM), powder X-ray diffractometry (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. The presence of Co defects regulated electronic structure of Co3O4, which not only speeds up electron transfer rate but also exposes more high-valent Co sites, thus improving electrocatalytic activities. Under optimized conditions, Co-defected Co3O4 electrode exhibited excellent performance for glucose analysis with a wide linear range of 0.2 µM to 0.5 mM, a low detection limit of 0.16 µM. Importantly, an ultrahigh sensitivity of 2595.7 µA·mM−1·cm−2 was also obtained, which was about 10 times higher than that of conventional Co3O4. Therefore, engineering Co3O4 with Co defects is an effective strategy to tailor electrocatalytic activity, which sheds light on the potential applications of metal defects in the field of electrochemical nonenzymatic sensing.

In Situ/Operando Soft X-ray Spectroscopic Identification of a Co4+ Intermediate in the Oxygen Evolution Reaction of Defective Co3O4 Nanosheets.

Defect engineering is an important means of improving the electrochemical performance of the Co3O4 electrocatalyst in the oxygen evolution reaction (OER). In this study, operando soft X-ray absorption spectroscopy (SXAS) is used to explore the electronic structure of Co3O4 under OER for the first time. The defect-rich Co3O4 (D-Co3O4) has a Co2.45+ state with Co2+ at both octahedral (Oh) and tetrahedral (Td) sites and Co3+ at Oh, whereas Co3O4 has Co2.6+ with Co2+ and Co3+ at Td and Oh sites, respectively. SXAS reveals that upon increasing the voltage, the Co2+ in D-Co3O4 is converted to low-spin Co3+, some of which is further converted to low-spin Co4+; most Co2+ in Co3O4 is converted to Co3+ but rarely to Co4+. When the voltage is switched off, Co4+ intermediates quickly disappear. These findings reveal Co(Oh) in D-Co3O4 can be rapidly converted to active low-spin Co4+ under operando conditions, which cannot be observed by ex situ XAS.

Vacancy and strain engineering of Co3O4 for efficient water oxidation

Co3O4 has been widely explored in electrocatalysis but seriously limited by its poor intrinsic ability. Defect engineering is an effective method to improve the electrocatalytic ability of catalysts by regulating electronic structure and optimizing the binding energy with surface adsorbates. Herein, in this work we have successfully integrated metal vacancies and tensile strain into Co3O4. With the formation of metal vacancies, the electronic structure of Co3O4 has been regulated. Moreover, the d-band center of Co3O4 has been modulated with the presence of tensile strain. The electrochemical oxygen evolution reaction (OER) ability of the obtained electrocatalyst was improved dramatically. The overpotential to reach 10 mA cm−2 was only 327 mV. Reaction kinetics was rapidly facilitated as indicated by smaller Tafel slope and charge transfer resistance. Density Functional Theory (DFT) calculations revealed that the relocated atoms induced the formation of tensile strain and made d-band center of electrocatalyst near to Fermi level leading to enhanced the adsorption to reaction intermediates. What’s more, the free energy barrier of rate-determining step (RDS) has been decreased with the integration of metal vacancies and tensile strain. This work provides an efficient strategy to develop defective and effective electrocatalysts.

Optical bandgap tuning of cubic spinel Co3O4 by annealing temperature

The optical bandgap of cubic normal spinel cobalt cobaltite (Co3O4) nanoparticles synthesized by the precipitation route has been studied. The tuning of the optical bandgap is demonstrated by annealing temperature at 400, 600, and 800°C. X-ray diffraction (XRD) analysis of all samples of Co3O4 nanoparticles confirms the single-phase cubic structure. The optical bandgap of Co3O4 nanoparticles at different annealed temperatures was studied by UV visible diffuse reflectance spectroscopy (DRS). The optical bandgap of Co3O4 nanoparticles increased as the annealing temperature varies from 400 to 800°C. The redistribution of Cobalt metal ions among the tetrahedral and octahedral sites of spinel Co3O4 structure moderated the optical bandgap with the increasing annealing temperature. The tetrahedral and octahedral peak's intensity ratios of XRD patterns, Raman spectroscopies, and FT-IR spectroscopies reveal the shifting of Co3+ ions from tetrahedral to the octahedral site, which leads to the increased optical bandgap.

Combined Corner‐Sharing and Edge‐Sharing Networks in Hybrid Nanocomposite with Unusual Lattice‐Oxygen Activation for Efficient Water Oxidation

AbstractCorner‐sharing and edge‐sharing networks are the two most important material genomes. Inspired by the efficient electron transport capacity of corner‐sharing structures and the low steric hindrance of edge‐sharing units, an attempt is made to exert both merits by combining these two networks. Here, a unique self‐assembled hybrid SrCo0.55Fe0.5O3‐δ nanorod composed of a corner‐sharing SrCo0.5Fe0.5O3‐δ phase and edge‐sharing Co3O4 structure is synthesized through a Co‐site enrichment method, which exhibits the low overpotentials of 310 and 290 mV at 10 mA cm–2 for oxygen‐evolving reaction in 0.1 m and 1.0 m KOH, respectively. This efficiency is attributed to the high Co valence with strong CoO covalence and the short distance between CoCo/Fe metal active sites in hybrid nanorods, realizing a synergistic benefit. Combined multiple operando/ex situ characterizations and computational studies show that the edge‐sharing units in hybrid nanorods can help facilitate the deprotonation step of lattice oxygen mechanism (LOM) while the corner‐sharing motifs can accelerate the electron transport during LOM processes, triggering an unusual lattice‐oxygen activation. This methodology of combining important material structural genomes can offer meaningful insights and guidance for various catalytic applications.

Potential of Piper betle@Co3O4 nanoparticles as high-performance photocatalysts for the removal of industrial dyes

In this study, cobalt oxide (Co3O4) NPs were bio-synthesized for photocatalytic application through the reduction of cobalt chloride hexahydrate using extract of Piper betle (e.g., polyphenols). The as-prepared Co3O4 NPs exhibited the face-centered cubic structure of Co3O4 with the crystallite sizes ranging from 20 to 30 nm with an energy band gap of 3.86 eV. FTIR spectra revealed that Piper betle extracts were present on the surface of the resulting Co3O4. HRTEM confirmed the dispersion of non-agglomerated uniformly spherical particles over a large area. The photocatalytic activity of the Co3O4 NPs was investigated for the degradation of the industrial dye, Eriochrome Black T (EBT). The degradation efficiency of EBT could exceed 94% within 80 min under UV light. The Piper [email protected]Co3O4 NPs recorded superior performance (quantum yield of 1.98 × 10−4 Φ and figure-of-merit of 1.59 × 10−9 mol L J−1 g−1 h−1) with a low energy requirement of 2.35 × 109 J mol−1. As such, the Piper betle@Co3O4 NPs are recognized as a high-efficiency photocatalyst for efficient degradation of industrial dyes.

Regulating electronic structure of hollow LaxCoyO4@NC by La incorporation for electrochemical oxygen evolution reaction

Developing efficient and low-cost electrocatalysts to substitute noble metals is crucial for oxygen evolution reaction (OER). Herein, we successfully synthesized hollow porous La-doped Co3O4 dodecahedral nanoparticles (LaxCoyO4@NC) through using ZIF-67 as precursor. Wherein, La could regulate electronic structure of Co3O4 and thus promotes the OER performance efficiently. La doped Co3O4 displays enhanced OER activity than pure Co3O4, as confirmed by experience results and density functional theory (DFT) calculation. Due to La doping, the ratio of Co2+ and Co3+ would increase obviously and generate new electronic states near the Fermi level. The La0.17Co2.83O4@NC exhibites excellent OER performance and high durability, which only requires an overpotential of 363 mV at the current density of 10 mA·cm−2 in alkaline medium and markedly outperforms Co3O4@NC (414 mV). These findings might provide a new strategy for controllable synthesis of transition metal nanocatalysts for high-performance OER electrocatalysis.

Co3O4 nanoparticles anchored on stable Na2Ti2O5 nanobelts for improved lithium storage

Co3O4, which is one of the many promising alternative candidates, promises a high capacity anode material. However, it suffers from large volume variation and slow reaction kinetics during the cycle. Herein, we demonstrate a facile, efficient method to tailor the structure of Co3O4 whereby improving its electrochemical performance significantly. The Co3O4 is tailored to ultrasmall 0D nanoparticles to anchor on the surface of 2D Na2Ti2O5 nanobelts (NTO) through a simple method. The established 0D/2D heterostructure interface provides a guarantee for structure durability and reaction kinetics of the entire NTO@Co3O4 composite anode during cycle. As expected, the results demonstrate that the NTO@Co3O4 exhibits improved performance over both NTO and Co3O4, revealing 927.2 mA h g−1 after 150 cycles at 200 mA g−1 and 782.5 mA h g−1 after 250 cycles at 1000 mA g−1. Besides simple preparation, the overall performance of NTO@Co3O4 is superior to those of other reported Co3O4-based two-transition metal oxide nanocomposites, therefore demonstrating the significance of this work.

Electron-Deficient Pd clusters induced by spontaneous reduction of support defect for selective phenol hydrogenation

A facile and green synthesis route to fabricate the stable and highly-dispersed Pd catalyst was reported by utilizing the reducibility and defect structure of Co3O4. Specifically, nanoshaped Co3O4 with different Co and O vacancies was prepared. Taking these as support, Pd2+ precursors were introduced and preferentially anchored in isolated Co vacancies, confirmed by density functional calculations. Notably, Pd2+ species were reduced by support without any reducing agent. More interestingly, as-obtained Pd catalysts exhibited different product distribution in selective phenol hydrogenation, whereas Pd/hexagonal Co3O4 only generated the cyclohexanol as product, while the cyclohexanone was dominant in rod and commercial Co3O4 supported Pd catalysts. This phenomenon was ascribed to electron-deficient Pd clusters influenced by Co vacancy in hexagonal Co3O4, facilitating further hydrogenation of reaction intermediate rather than desorption. This work provides a feasible way to construct well-distributed and electron-deficient Pd clusters, offering an opportunity to control product distribution in selective hydrogenation.

A novel hybridized needle-like Co3O4/N-CNO composite for superior energy storage asymmetric supercapacitors

The controlled growth of needle-like Co3O4 and composite formation with highly graphitic carbons such as N-CNOs is critically essential for obtaining high-performance energy storage supercapacitors. In this study, the needle-like Co3O4 and graphitic N-CNOs are synthesized by the simple solvothermal and pyrolysis methods, respectively. The Co3O4/N-CNO composite enhances the fast charge transfer by reducing ion diffusion. The Co3O4/N-CNO composite demonstrated an improved specific capacitance (3066 F g−1) than the needle-like structure of Co3O4 (2068 F g−1). The Co3O4/N-CNO composite exhibited very good rate capability and high capacitance retention of 82% at a high current density of 8 A g−1 meanwhile the Co3O4/N-CNO//AC ASC device shows high power and energy densities with capacitance retention of 78% and Coulombic efficiency of 100% over 2000 cycles. This attractive electrochemical performance of Co3O4/N-CNO composite makes it a favorable device for practical applications of supercapacitors.