Co3O4 Precursor Research Articles

Modulating Silver Performance in Electrocatalytic Oxidation of HCHO via SMSI between Ag-Co3O4 Interfaces.

The replacement of oxygen evolution reactions with organic molecule oxidation reactions to enable energy-efficient hydrogen production has been a subject of interest. However, further reducing reaction energy consumption and releasing hydrogen from organic molecules continue to pose significant challenges. Herein, a strategy is proposed to produce hydrogen and formic acid from formaldehyde using Ag/Co3O4 interface catalysts at the anode. The key to improving the performance of Ag-based catalysts for formaldehyde oxidation lies in the strong SMSI achieved through the well-designed "spontaneous redox reaction" between Ag and Co3O4 precursors. Nano-sized Ag particles are uniformly dispersed on Co3O4 nanosheets, and electron-deficient Agδ+ are formed by the SMSI between Ag and Co3O4. Ag/Co3O4 demonstrates exceptional formaldehyde oxidation activity at low potentials of 0.32V versus RHE and 0.65V versus RHE, achieving current densities of 10 and 100mA cm-2, respectively. The electrolyzer "Ag/Co3O4||20% Pt/C" achieves over 195% hydrogen efficiency and over 98% formic acid selectivity, maintaining stable operation for 60 hours. This work not only presents a novel approach to precisely modulate Ag particle size and interface electronic structure via SMSI, but also provides a promising approach to efficient and energy-saving hydrogen production and the transformation of harmful formaldehyde.

Visualizing Phase Evolution of Co2C for Efficient Fischer-Tropsch to Olefins.

Cobalt carbide (Co2C) possesses high catalytic efficiency Fischer-Tropsch synthesis (FTS), while the products selectivity appears sensitive to crystallography geometry. Since the Anderson-Schulz-Flory (ASF) distribution in FTS is broken through fabricating facetted Co2C nanocrystals, yet the underlying mechanism of Co2C crystallization remains unclarified suffering from sophisticated catalyst composition involving promoter agents. Herein, the synthesis of high-purity single-crystal nanoprisms (Co2C-p) for highly efficient FTS is reported to lower olefins. Through comprehensive microstructure analysis, e.g., high-resolution TEM, in situ TEM and electron diffraction, as well as finite element simulation of gas flow field, for the first time the full roadmap of forming catalytic active cobalt carbides is disclosed, starting from reduction of Co3O4 precursor to CoO intermediate, then carburization into Co2C-s and subsequent ripening growth into Co2C-p. This gas-induced engineering of crystal phase provides a new synthesis strategy, with many new possibilities for precise design of metal-based catalyst for diverse catalytic applications.

Electrochemical activation of venus flytrap-like CoP and Co3O4 for boosting the supercapacitance performance

Electrochemical activation tactic can be adopted to boost electrochemical performance of electrodes by adjusting the composition and microstructure. Herein, venus flytrap-like CoP nanostructures and corresponding Co3O4 precursor are synthesized on nickel foam (NF) framework, and the electrochemical activation mechanisms of CoP and Co3O4 are investigated in KOH electrolyte. When endured for 100 CV cycles, the activated CoP exhibits a 3D framework structure consisted of thin nanosheets, and the discharge capacity enhances to 1536 C g−1 at 1 A g−1 from initial capacity of 663 C g−1. The enhanced performance is due to the composition transition from upper CoP and beneath NiP to NiCo-hydroxides and NiCoOOH, and the microstructure transition from nanoneedles to 3D framework structure stacked by thin nanosheets. Different from the transition mechanism of NF/CoP, seldom microstructure transitions are occurred for the Co3O4 precursor, only involving the change of nanoneedle diameter. The activation of Co3O4 induces a limited capacity enhancement from 242 to 623 C g−1, due to a simple transition from oxides to oxyhydroxides. The application performance of NF/CoP is investigated by assembling asymmetric supercapacitor with NF/AC. The device releases a discharge capacitance of 137 F g−1 at 1 A g−1, and the capacitance retention is 77.4% when cycling for 5000 cycles. The energy density is 48.7 W h kg−1 at 804.4 W kg−1. Compared with existing Co-based phosphides, activated NF/CoP electrode exhibits an obvious performance advantage in supercapacitors.

Co3O4 electronic-structure tuning via Se doping for peroxymonosulfate activation: Synergy of reactive-oxygen species generation and adsorption–desorption strength

Increasing peroxymonosulfate (PMS) activation efficiency by Co3O4 to produce more reactive sites remains a challenge. Here, we report Se doping to simultaneously tune oxygen vacancy densities, Co2+ active site levels, and the Co3O4 3d-band center for activating PMS to degrade levofloxacin (LEV). The Se-doped Co3O4 (Se@Co3O4) was fabricated by pyrolyzing a mixture of Se powder and Co3O4 precursors. It had many more Co2+ active sites and oxygen vacancies relative to Co3O4. This favored generation of reactive oxygen species that degraded LEV in bulk solution. Density functional theory calculations revealed a downshift of the Co 3d-band in Se@Co3O4 with an enhanced electron-donating ability and an optimized adsorption–desorption strength, which increased reactive oxygen production and subsequent leave from hetero-surface to extinct LEV in bulk solution. Se@Co3O4 exhibited over 95% degradation of 10 mg/L LEV with 0.2 g/L PMS activated within 25 min at 25 °C, while Co3O4 exhibited 20% degradation under the same conditions. The first-order rate constant for LEV degradation by Se@Co3O4 was approximately 42 times that of Co3O4, and it exhibited good PMS activation over the pH range 5.0–9.0. LEV degradation conditions and effects of water matrices were optimized and explored, respectively. The Se@Co3O4/PMS system could still degrade over 85% of LEV after five cycles, as well as pefloxacin, p-nitrophenol, tetracycline and rhodamine B. This suggests its excellent universality. The potential mechanism of PMS activation by the Se@Co3O4 and probable LEV degradation routes were discussed based on the outcomes of active reactive species tests and LEV degradation intermediates confirmed by liquid chromatography-mass spectrometry. This work revealed that Se doping promoted electronic modulation in Se@Co3O4 for PMS activation, and indicated potential high-performance Fenton-like catalysts.

Acetone hydrogenation over face-centered cubic and hexagonal close-packed cobalt

Acetone hydrogenation is employed for investigating the structure sensitivity of H2 activation over cobalt catalysts while the produced isopropanol garners increasing interest in the sustainable energy context e.g. as H2 storage material and fuel for direct fuel cells. Both hexagonal close-packed (hcp) and face-centered cubic (fcc) Co can produce isopropanol with 100% selectivity below 150 °C with the reaction proceeding almost ten times faster over hcp Co. Hydrogenation rates are even higher over an hcp Co/Co3O4 composite which remains highly selective to isopropanol despite that Co3O4 yields mostly mesityl oxide and related products. The superior performance of hcp Co and its composite are attributed to efficient generation of atomic H on the metal and the presence of stronger sites for acetone activation on XRD-amorphous phases that are formed during reduction of the Co3O4 precursor at 250 °C and 400 °C. These findings provide insight into the optimum structural design of highly active and selective low-temperature cobalt hydrogenation catalysts.

Efficient and Stable Anode Material for Li Batteries: Utilizing Co3O4 Nanoparticles Modified Active Graphite Derived from Date Pulp

To date, there has been extensive research conducted on Li-ion batteries to address the challenge of achieving both safety and high energy density. This paper describes the successful synthesis of an anode material for lithium storage with exceptional performance by utilizing cobalt nitrate as a Co3O4 precursor and dates as a carbon source. The carbon derived from the dates possesses several desirable properties, including a high specific surface area, hierarchical arrangement, satisfactory electronic conductivity, and remarkable mechanical flexibility. This carbon effectively maintains the stability of large-capacity Co3O4 particles. The electrochemical behavior of lithium cells containing the fabricated carbon electrodes was analyzed using various electrochemical techniques. As a result, the carbon–metal oxide composite electrodes in lithium-ion batteries exhibit satisfactory reversible capacity, cycling stability, Coulombic efficiency, and comparatively high-rate capability, which can be attributed to their unique structure that facilitates the rapid transport of Li+ ions.

Lattice Compressive Strain of Co3O4 Induced by Synthetic Solvents Promotes Efficient Oxidation of Benzene at Low Temperature.

A series of Co3O4 with different surface defective structures were prepared by the solvothermal method and tested for the activity of benzene oxidation. The characterizations revealed that the synthetic solvent had a dramatic effect on the composition of Co3O4 precursors as well as the physicochemical properties of Co3O4. Although all Co3O4 exhibited a cubic spinel structure, Co3O4 prepared with triethylene glycol (Co-TEG) had the highest compressive strain due to the nature of high viscosity of triethylene glycol. These in turn affected the surface chemical structure and the low-temperature redox properties. Co-TEG exhibited the best benzene oxidation activity and showed excellent stability and good water resistance. In situ diffuse reflectance infrared Fourier transform spectroscopy was used to study the oxidation process of benzene. It was found that Co-TEG with more defective structures had abundant surface adsorbed oxygen and active lattice oxygen, which promoted the conversion of benzene and the corresponding intermediates at low temperature.

Anodic polarization characteristics in hydrogen and methane oxidations at nickel-cobalt yttria-stabilized zirconia cermet relating to prolonged cell performance stability

The conventional solid oxide fuel cell (SOFC) anode, which consists of metallic Ni and yttria-stabilized zirconia (YSZ), is liable to deactivation when a carbon-containing gaseous fuel is directly supplied. To retard the degradation due to a direct supply of CH4, the Ni/YSZ has been modified with the incorporation of Co into the Ni matrix, forming a substitutional solid-solution alloy. As a result, the porous anode exhibits well-connected compositional grains owing to the Co3O4 precursor as a sintering aid. The 25 mol% Co incorporation producing the Ni0.75Co0.25/YSZ anode significantly improves the cell performance and prolonged stability. In addition, the Ni0.75Co0.25/YSZ anode provides the apparent activation energy of the charge transfer reaction to a lower value in the electrochemical oxidation of CH4 at the triple-phase boundary. However, the apparent activation energy decrease is not identified for H2. The Co alloying effect on catalyzing the electrochemical oxidation of CH4 is caused by suppressing the carbon deposition originating from the thermal dissociation of adsorbed CH4 on the Ni1-xCox alloy surface.

Long-term cycling behavior of Mg-doped LiCoO2 materials investigated with the help of laboratory scale X-ray absorption near-edge spectroscopy

The use of Li-ion batteries is increasing rapidly. Understanding the processes behind active material aging helps to enhance the materials, and therefore, development of new in situ methods for structural studies is important. In addition, understanding the effect of different synthesis methods on the active material properties is necessary to optimize the material cycle life. In this work, the performance of LiCoO2 doped with Mg during the lithiation step is compared to LiCoO2 prepared using an Mg-doped Co3O4 precursor. In situ laboratory-scale X-ray absorption near-edge spectroscopy is used to analyze the Co valence changes in LiCoO2 to understand the electrochemical behavior of the investigated materials. The maximum reachable Co valence state is found to decrease upon aging, a small decrease indicating a good cycle-life, and this is attributed to the enhanced stacking order, better Mg distribution in the lattice, and fine primary particle size in the material. In the synthesis conditions used in this study, Mg doping during the lithiation step is shown to perform better compared to the precursor doping. Overlithiation is shown to reduce the electrochemical performance of nondoped and precursor-doped LiCoO2 materials but not to affect the cyclability of lithiation-doped LiCoO2.

Improved solid interfacial kinetics and electrochemical performance for LiCoO2(1 1 0) textured thin-film lithium batteries

The solid-solid interfaces have crucial, but still poorly understood, roles in the performance of thin-film lithium batteries (TFBs). The modulating of crystalline preferred growth orientation is an effective method to build rapid ionic diffusion channel with lower interfacial barrier. This work develops and reveals the interfacial electrochemical behaviors of textured cathode/solid electrolyte in TFBs by controlling preferred growth orientation of LiCoO2 (LCO) thin-film. The LCO(003) texture is transformed from the (440) plane of Co3O4 precursor with the lowest surface energy after annealing. Remarkably, oxygen reactive sputtering will promote the formation of LCO grains instead of Co3O4 species, resulting in the growth of LCO along (110) facet with the lowest volume strain-energy after annealing. TFBs (LCO/LiPON/Li) configuration with LCO(110) texture exhibit enhanced electrochemical performance with the capacity of about 101 mAh g−1 about twice than that of (003) texture on 10C-rates, owing to the lower interface and bulk resistance. These results indicate that the method of controlling the lattice orientation not only minimize the lithium-ion diffusion pathways in the film textures, but also is beneficial to the interface between LCO and LiPON electrolyte to establish high performance solid-state batteries.

Heterostructured CoO/Co3O4 nanowire array on Titanium mesh as efficient electrocatalysts for hydrogen evolution reaction

Heterostructured CoO/Co3O4 nanowire array on Titanium mesh (CoO/Co3O4 NA/Ti) is fabricated via a facile controllable calcination treatment of the Co3O4 precursor in a reducing atmosphere (H2/Ar) and applied as efficient electrocatalyst for hydrogen evolution reaction (HER). This electrode could catalyze the HER in 1.0 M KOH electrolyte with initial overpotential as low as 2.7 mV and need overpotential of 108 mV to approach 10 mA cm−2. Remarkably, it also shows high catalytical activity and long-time durability for HER both in phosphate buffer saline (PBS) and NaCl solution. This work may inspire the design of other high-performance three dimensional-nanostuctured (3D-nanostuctured) HER catalysts with abundant heterojunction interfaces.

CoxP@Co3O4 Nanocomposite on Cobalt Foam as Efficient Bifunctional Electrocatalysts for Hydrazine-Assisted Hydrogen Production

The kinetically sluggish oxygen evolution reaction (OER) at an anode has always been the bottleneck in the large-scale application of electrocatalytic water splitting to produce ecofriendly and sustainable hydrogen. Therefore, replacing the OER with hydrazine oxidation reaction (HzOR), which requires a lower theoretical potential, has been considered as a more energy-efficient strategy. Herein, a novel bifunctional CoₓP@Co₃O₄ nanocomposite with grass-like and block-like structures was fabricated on Co foam (defined as P–Co₃O₄/Co) via a facile hydrothermal synthesis for Co₃O₄ and the sodium hypophosphite-phosphorization method for cobalt phosphides. Compared with the Co₃O₄ precursor on Co foam, the heterogeneous P–Co₃O₄/Co, composed of a mixture of CoP, Co₂P, and Co₃O₄, possessed superb electrochemical catalytic activity for both the hydrogen evolution reaction and HzOR in 1.0 M KOH and 0.3 M hydrazine medium. Low overpotentials of 106 and 129 mV were required to deliver current densities of 10 and 200 mA cm–², respectively. Meanwhile, potentials of −100 and −83 mV are needed to drive current densities of 10 and 200 mA cm–², respectively, which exceed those of almost recently reported catalysts. The excellent performance can be attributed to the fact that the synergistic effect between the presence of multiphase of CoₓP/Co₃O₄ and the three-dimensional porous Co foam substrate makes the as-synthesized catalyst possess a large specific surface area and fast charge/mass transport. Density functional theory calculations unravel that the phosphorization strategy can not only regulate the electronic structure of pristine Co₃O₄, enhancing the electronic conductivity, but also optimize the adsorption/desorption strength of H* and alter the free energy change of the dehydrogenation kinetics of NH₂NH₂*. Meanwhile, a low cell voltage of 1 V was achieved to deliver a current density of 948 mA cm–² when P–Co₃O₄/Co behaved as both the cathode and anode simultaneously, which was superior to most of the nonprecious metal-based catalysts.

Green gelatin-assisted: Synthesis of Co3O4NPs@rGO nanopowder for highly efficient magnetically separable methylene orange dye degradation

GO and Co(NO3)2 were respectively used as rGO and Co3O4 precursors for preparing magnetically separable Co3O4NPs attached Co3O4NPs@rGO nanocomposites by a straightforward sol–gel technique. To characterize the nanocomposite materials, FESEM, EDX, elemental mapping, XRD, FTIR, Raman spectroscopy, UV–vis, VSM and BET were employed. When exposed to UV rays, the nanocomposite showed extraordinary photocatalytic degradation of MO dye. According to the measurements of photocatalytic activity, the highly efficient photocatalytic efficiency of the nanocomposite could be attributed to preventing electron-hole recombination by highly effective electron transfer between rGO and semiconductor NPs. The nanocomposite succeeded in the efficient degradation of MO dye, even after five photocatalytic cycles.

Construction of SnO2/Co3O4 n-p heterojunctions by organometallic chemistry-assisted approach

SnO2/Co3O4 n-p heterojunctions have been prepared by organometallic chemistry-assisted approach, where holy Co3O4 nanosheets and (CH3)2SnCl2were used as precursors. It is found that the surface oxygen-containing species could be regulated by changing the ratio of Co3O4 precursors and Sn-containing organic compound. Our present work is of importance because it provides a new and effective approach for construction of heterojunctions.

Tunable S doping from Co3O4 to Co9S8 for peroxymonosulfate activation: Distinguished Radical/Nonradical species and generation pathways

The introduction of non-metal heteroatoms is an effective way to improve the catalytic properties of heterogeneous catalysts to peroxymonosulfate. Unfortunately, the influence of foreign elements on the catalytic process has not been deeply revealed. Herein, we reported a series of Co9S8 nanorods catalysts from Co3O4 precursor with different S doping ratios. S doping effectively enhanced the catalytic properties, and the catalytic process gradually switched from non-radical (1O2) into radical (SO4−) with the increase of S doping ratio. Moreover, quenching experiments, EPR, XPS, and radicals quantification indicated that the concentration of 1O2 exhibited a linear relationship with ΔOL. Indicating that 1O2 was derived from the reaction between PMS and OL. S doping also altered the valency of cobalt. In Co3O4/PMS, ROS was generated through Co3+/Co2+ catalytic circle. However, in Co9S8/PMS, Co3+/Co2+/Co0 were all involved and accounted for the generation of ROS due to the low redox potential of S2-. Our work may provide some new clues and strategies for studying the influence of foreign elements on the catalytic process in PMS-based heterogeneous catalytic system.

Co3O4 nanoparticles/graphitic carbon nitride heterojunction for photoelectrochemical aptasensor of oxytetracycline

As a broad-spectrum tetracycline antibiotic, the overuse of oxytetracycline (OTC) causes antibiotics residues in the environment and seriously threats to human health owing to effective antibacterial properties. Thus, it is particularly important to design a photoelectrochemical (PEC) aptasensor to detect OTC with excellent performance. Herein, we developed a selective and stable PEC aptasensor of OTC on the basis of Co3O4 nanoparticles (Co3O4 NPs)/graphitic carbon nitride (g-CN) heterojunction, used as PEC active materials. The Co3O4 NPs were successfully grown on the g-CN via grinding and calcining mixture of Co3O4 precursors and bulk g-CN. The Co3O4/g-CN heterojunction with improved light utilization and promoted electrons/holes separation capability can exhibit higher PEC signal than that of g-CN. In order to implement the purpose of specific recognition, OTC-aptamer was introduced into modified electrode to construct highly selective PEC aptasensor for OTC determination, which can possess wide linear range (0.01–500 nM) with low detection limit (3.5 pM, S/N = 3). This PEC aptasensor platform with excellent selectivity and high stability can provide a practical application in the field of water monitoring.

Combustion of toluene over cobalt-modified MFI zeolite dispersed on monolith produced using 3D printing technique

A facile method of fabrication of ceramic monoliths assisted by 3D printing was developed for preparation of Co3O4-based catalysts of total oxidation of volatile organic compounds. The proposed approach was based on the production of a resin template, which was subsequently used at a casting step for the construction of corundum monolith. The walls of this material were additionally coated with a MFI zeolite layer providing the possibility of modification with a Co3O4 precursor using ion-exchange and impregnation techniques. The parent and Co3O4-modified monoliths with varying active phase content were characterized by SEM/EDS, XRD, XRF, XPS, UV–vis-DR and H2-TPR. Their catalytic performance in the toluene combustion was also tested. It was shown that the formation of Co3O4 spinel particles highly dispersed on the zeolite-coated monolith resulted in excellent catalytic activity measured by very high TOF values. Furthermore, stability tests confirmed that the obtained monolith catalysts can work for prolonged reaction time without noticeable changes in the toluene conversion and selectivity to CO2.

Reaction mechanism and thermoelectric properties of In0·22Co4Sb12 prepared by magnesiothermy

The magnesioreduction synthesis of In0·22Co4Sb12 with high In rattler concentration from Sb2O4 and In-doped Co3O4 precursors is reported. This process directly yields a submicronic powder in a single step of 96 h at 810 K. The reaction mechanism has been investigated by stopping the reaction every 12 h and quantifying the existing phases by X-ray diffraction and Rietveld refinements. The precursors are first reduced in CoO and Sb2O3 lower oxides, then form CoSb2O6 and CoSb2O4 intermediates which are finally reduced in InxCo4Sb12. A powder with 350 nm average size and mostly composed of In-filled skutterudite phase with composition close to In0·17Co4Sb12 is obtained. Upon spark plasma sintering, small residual amount of InSb reacts with the skutterudite matrix to form a single-phase densified pellet with composition close to In0·22Co4Sb12. The resulting densified material with 1.8 μm average grain size shows a figure of merit ZTmax of 0.95 at 750 K.

Three-Dimensional Precursor-Derived Synthesis of Co3O4 Towards High Electrochemical Performance

Three-dimensional (3D) cobalt oxide (Co3O4) flowers with different shapes were prepared by a facile hydrothermal synthesis. The morphology of Co3O4 precursors has adjusted obviously from acicular shapes to acicular-sheet-like flowers and then to sheet-like flowers by changing reaction temperature and solution concentration. After annealing, as-prepared precursors were converted into 3D flower-like Co3O4 samples and their morphology and sizes were well preserved. The effect of experimental conditions on growth of Co3O4 precursors was explored and the growth mechanism was proposed. Moreover, the electrochemical properties of various Co3O4 with different shapes were tested. The result of electrochemical investigation indicates that 3D flower-like Co3O4 assembled by sheets exhibited high capacitance and excellent cycling performance.

Cobalt‐Based Catalyst Supported on Different Morphologies of Alumina for Non‐oxidative Propane Dehydrogenation: Effect of Metal Support Interaction and Lewis Acidic Sites

AbstractDeveloping an economically viable and eco‐friendly catalyst is essential for the dehydrogenation reaction. In this context, cobalt‐based catalysts supported on different morphologies of γ‐Al2O3, nano‐sheet (Al2O3−NS), nano‐fiber (Al2O3−NF) and nano‐plate (Al2O3−NP) were synthesized using wetness impregnation method and tested for non‐oxidative propane dehydrogenation reaction. Metal support interaction and Lewis acidic center play a crucial role in propane dehydrogenation reaction; therefore this study focuses on investigating the role of these parameters on the catalytic activity for cobalt‐based catalysts. A higher metal support interaction was observed in Co/Al2O3−NS as compared to Co/Al2O3−NF and Co/Al2O3−NP. The presence of tetrahedral coordinated Co+2 in Co/Al2O3−NS leads to higher selectivity towards propylene. The formation of metallic cobalt from Co3O4 precursor present in Co/Al2O3−NP promoted side reactions to form lower hydrocarbons and carbon, which caused catalyst deactivation. In‐situ DRIFTS analysis revealed the interaction of propane and propylene gases with the catalyst, which was an important revelation to find the source of carbon deposition.