Cobalt oxide nanocubes as electrode material for the performance evaluation of electrochemical supercapacitor

Porous cobalt oxide (Co₃O₄) nanocubes (NCs) were synthesized by a simple and cost-effective hydrothermal technique for the potential application of electrochemical supercapacitors. The hydrothermally synthesized materials exhibited the small cube like morphology with the average size of ~ 50 to 60 nm. The surface analysis revealed a good surface area, and high pore volume of the synthesized porous Co₃O₄ NCs. The capacitive properties of porous Co₃O₄ NCs electrode were investigated by cyclic voltammetry (CV) in 6 M KOH electrolyte and a high specific capacitance of ~ 430.6 F/g at a scan rate of ~ 10 mV s^?1 was observed. The capacity retention of up to ~ 85% after 1000 cycles was shown by the fabricated porous Co₃O₄ NCs electrode. The porous Co₃O₄ NCs showed excellent structural stability through cycling with promising capacity retention which suggested a good quality of porous Co₃O₄ NCs as electrochemical supercapacitor electrode.     

Cobalt oxide nanocomposites and their electrocatalytic behavior for oxygen evolution reaction

In this work, we have described the simple preparation method of cobalt oxide nanocomposites where cobalt oxide nanoparticles were grown on the surface of carbon nanotube, graphene oxide and graphene (Co₃O₄@CNT, Co₃O₄@GO, Co₃O₄@G). The as-grown Co₃O₄@CNT, Co₃O₄@GO, Co₃O₄@G were investigated for H₂O oxidation. The nanoparticles displayed high activity toward oxygen evolution. Further, the stability of the catalysts were tested in alkaline solution, which exhibited good stability. Among all nanoparticles, Co₃O₄@G exhibited higher current density at lower overpotential and also exhibited lower Tafel slope (157.1 mV dec⁻¹) as compared to Co₃O₄@CNT and Co₃O₄@GO. The Co₃O₄@G delivered a current density of 10 mAcm⁻² at 0.8 V (overpotential 535 V versus Ag/AgCl) in 0.1 M KOH solution, which is superior than many electrocatalysts reported for oxygen evolution so far. The good electrocatalytic performance might be due to the structural features of Co₃O₄@G, which cause enhancement of oxygen evolution activity.     

Preparation of Three-Dimensional Co3O4/graphene Composite for High-Performance Supercapacitors

Here, we developed a simple and efficient route for the preparation of three-dimensional (3D) Co₃O₄-anchored graphene composites using the sacrificial template-assisted method and the subsequent deposition process of Co₃O₄ nanoparticles. As structural guiding materials, polystyrene (PS) spheres provide 3D porous architectures with a high surface area. 3D porous graphene materials serve as conductive supporters for the deposition of Co₃O₄ nanoparticles through precipitation growth. The 3D porous composite structures of Co₃O₄/graphene composites were intensively investigated using scanning electron microscope, transmission electron microscope, and X-ray diffraction. The 3D Co₃O₄/graphene composites show a high specific capacitance of 328?F?g^?1 with efficient and fast charge–discharge process in aqueous 6?M KOH electrolyte. In addition, the composites provide a good cycle lifetime, which retained 98% capacitance retention over 2000 cycles.     

One-pot dual product synthesis of hierarchical Co3O4@N-rGO for supercapacitors,N-GDs for label-free detection of metal ion and bio-imaging applications

Cobalt oxide nanoparticles@nitrogen-doped reduced graphene oxide (Co₃O₄@N-rGO) composite and nitrogen-doped graphene dots (N-GDs) were synthesized by a one-pot simple hydrothermal method. The average sizes of the synthesized bare cobalt oxide nanoparticles (Co₃O₄ NPs) and Co₃O₄ NPs in the Co₃O₄@N-rGO composite were around 22 and 24 nm, respectively with an interlayer distance of 0.21 nm, as calculated using the XRD patterns. The Co₃O₄@N-rGO electrode exhibits superior capacitive performance with a high capability of about 450 F g^?1 at a current density of 1 A g^?1 and has excellent cyclic stability, even after 1000 cycles of GCD at a current density of 4 A g^?1. The obtained N-GDs exhibited high sensitivity and selectivity towards Fe²⁺ and Fe³⁺, the limit of detection was as low as 1.1 and 1.0 μM, respectively, representing high sensitivity to Fe²⁺ and Fe³⁺. Besides, the N-GDs was applied for bio-imaging. We found that N-GDs were suitable candidates for differential staining applications in yeast cells with good cell permeability and localization with negligible cytotoxicity. Hence, N-GDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe³⁺/Fe²⁺) and also for early detection of opportunistic yeast infections in biological samples.     

Achieving ultra-high electromagnetic wave absorption by anchoring Co0.33Ni0.33Mn0.33Fe2O4 nanoparticles on graphene sheets using microwave-assisted polyol method

The Co_0.33Ni_0.33Mn_0.33Fe₂O₄/graphene nanocomposite for electromagnetic wave absorption was successfully synthesized from metal chlorides solutions and graphite powder by a simple and rapid microwave-assisted polyol method via anchoring the Co_0.33Ni_0.33Mn_0.33Fe₂O₄ nanoparticles on the layered graphene sheets. The Fe³⁺, Co²⁺, Ni²⁺ and Mn²⁺ ions in the solutions were attracted by graphene oxide obtained from graphite and converted to the precursors Fe(OH)₃, Co(OH)₂, Ni(OH)₂, and Mn(OH)₂ under slightly alkaline conditions. After the transformations of the precursors to Co-Ni-Mn ferrites and conversion of graphene oxide to graphene under microwave irradiation at 170?°C in just 25?min, the Co_0.33Ni_0.33Mn_0.33Fe₂O₄/graphene nanocomposite was prepared. The composition and structure of the nanocomposite were characterized by X-ray diffraction (XRD), inductive coupled plasma emission spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), transmission electron microscopy (TEM), etc. It was found that with the filling ratio of only 20?wt% and the thickness of 2.3?mm, the nanocomposite showed an ultra-wide effective absorption bandwidth (less than ?10?dB) of 8.48?GHz (from 9.52 to 18.00?GHz) with the minimum reflection loss of ??24.29?dB. Compared to pure graphene sheets, Co_0.33Ni_0.33Mn_0.33Fe₂O₄ nanoparticles and the counterparts reported in literature, the nanocomposite exhibited much better electromagnetic wave absorption, mainly attributed to strong wave attenuation, as a result of synergistic effects of dielectric loss, conductive loss and magnetic loss, and to good impedance matching. In view of its thin thickness, light weight and outstanding electromagnetic wave absorption property, the nanocomposite could be used as a very promising electromagnetic wave absorber.     

Towards high purity graphene/single-walled carbon nanotube hybrids with improved electrochemical capacitive performance

CoMgAl layered double hydroxides were prepared as catalysts for the in situ synchronous growth of graphene and single-walled carbon nanotubes (SWCNTs) from methane by chemical vapor deposition. The as-calcined CoMgAl layered double oxide (LDO) flakes served as the template for the deposition of graphene, and Co nanoparticles (NPs) embedded on the LDOs catalyzed the growth of SWCNTs. After the removal of CoMgAl LDO flakes, graphene (G)/SWCNT/Co₃O₄ hybrids with SWCNTs directly grown on the surface of graphene and 27.3 wt.% Co₃O₄ NPs encapsulated in graphene layers were available. Further removal of the Co₃O₄ NPs by a CO₂-oxidation assistant purification method induced the formation of G/SWCNT hybrids with a high carbon purity of 98.4 wt.% and a high specific surface area of 807.0 m²/g. The G/SWCNT/Co₃O₄ hybrids exhibited good electrochemical performance for pseudo-capacitors due to their high Co₃O₄ concentration and the high electrical conductivity of SWCNTs and graphene. In another aspect, the G/SWCNT hybrids can be used as excellent electrode materials for double-layer capacitors. A high capacity of 98.5 F/g_electrode was obtained at a scan rate of 10 mV/s, 78.2% of which was retained even when the scan rate increased to 500 mV/s.     

Graphene non-covalently tethered with magnetic nanoparticles

We describe a novel approach for coupling pristine graphene with superparamagnetic iron oxide nanoparticles to create dispersed, magnetically responsive hybrids. The magnetic iron oxide (Fe₃O₄) nanoparticles are synthesized by a co-precipitation method using ferric (Fe³⁺) and ferrous (Fe²⁺) salts and then grafted with polyvinylpyrrolidone (PVP). These PVP-grafted Fe₃O₄ nanoparticles are then used to stabilize colloidal graphene in water. The PVP branches non-covalently attach to the surface of the pristine graphene sheets without functionalization or defect creation. These Fe₃O₄–graphene hybrids are stable against aggregation and are highly responsive to external magnetic fields. These hybrids can be freeze-dried to a powder or magnetically separated from solution and still easily redisperse while retaining magnetic functionality. At all stages of synthesis, the Fe₃O₄–graphene hybrids display no coercivity after being brought to magnetic saturation, confirming superparamagnetic properties. Microscopy and light scattering data confirm the presence of pristine graphene sheets decorated with Fe₃O₄ nanoparticles. These materials show promise for multifunctional polymer composites as well as biomedical applications and environmental remediation.     

Magnetic Properties of FeMn<Subscript>y</Subscript>Co<Subscript>y</Subscript>Fe<Subscript>2−2y</Subscript>O<Subscript>4</Subscript>@Oleylamine Nanocomposite with Cation Distribution

In this study, oleylamine (OAm) capped FeMn_yCo_yFe_2?2yO₄ (0.0?≤?y?≤?0.4) nanocomposites (NCs) were prepared via the polyol route and the impact of bimetallic Co³⁺ and Mn³⁺ ions on the structural and magnetic properties of Fe₃O₄ was investigated. The complete characterization of FeMn_yCo_yFe_2?2yO₄@OAm NCs were done by different techniques such as XRD, SEM, TGA, FT-IR, TEM, and VSM. XRD analyses proved the successful formation of mono-phase MnFe₂O₄ spinel cubic products free from any impurity. The average crystallite sizes were calculated in the range of 9.4–26.4 nm using Sherrer’s formula. Both SEM and TEM results confirmed that products are nanoparticles like structures having spherical morphology with small agglomeration. Ms continued to decrease up to Co³⁺ and Mn³⁺ content of y?=?0.4. Although Mössbauer analysis reveals that the nanocomposites consist three magnetic sextets and superparamagnetic particles are also formed for Fe₃O₄, Co_0.2Mn_0.2Fe_2.6O₄ and Co_0.4Mn_0.4Fe_2.2O₄. Cation distributions calculation was reported that Co³⁺ ions prefer to replace Fe²⁺ ions on tetrahedral side up to all the concentration while Mn³⁺ ions prefer to replace Fe³⁺ ions on the octahedral.     

Characteristics of Cu and Mo-doped Ca3Co4O9−δ cathode materials for use in solid oxide fuel cells

In this study, Cu and Mo ions were doped in Ca₃Co₄O_9−δ to improve the electrical conductivity and electrochemical behavior of Ca₃Co₄O_9−δ ceramic and the performance of a solid oxide fuel cell (SOFC) single cell based on NiO-SDC/SDC/doped Ca₃Co₄O_9−δ-SDC were examined. Cu substitution in the monoclinic Ca₃Co₄O_9−δ ceramic effectively enhanced the densification, slightly increased the grain size, and triggered the formation of some Ca₃Co₂O₆; however, no second phase was found in porous Mo-doped Ca₃Co₄O_9−δ ceramics even when the sintering temperature reached 1050 °C. Substitution of Cu ions caused slight increase in the Co³⁺ and Co⁴⁺ contents and decrease in the Co²⁺ content; however, doping with Mo ions showed the opposite trend. Doping the Ca₃Co₄O_9−δ ceramic with a small amount of Cu or Mo increased its electrical conductivity. The maximum electrical conductivity measured was 218.8 S cm⁻¹ for the Ca₃Co_3.9Cu_0.1O_9−δ ceramic at 800 °C. The Ca₃Co_3.9Cu_0.1O_9−δ ceramic with a coefficient of thermal expansion coefficient of 12.1×10⁻⁶ K⁻¹ was chosen as the cathode to build SOFC single cells consisting of a 20 μm SDC electrolyte layer. Without optimizing the microstructure of the cathode or hermetically sealing the cell against the gas, a power density of 0.367 Wcm⁻² at 750 °C was achieved, demonstrating that Cu-doped Ca₃Co₄O_9−δ can be used as a potential cathode material for IT-SOFCs.     

Highly reversible Co3O4/graphene hybrid anode for lithium rechargeable batteries

A Co₃O₄/graphene hybrid material was fabricated using a simple in situ reduction process and demonstrated as a highly reversible anode for lithium rechargeable batteries. The hybrid is composed of 5 nm size Co₃O₄ particles uniformly dispersed on graphene, as observed by transmission electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray diffraction analysis. The Co₃O₄/graphene anode can deliver a capacity of more than 800 mA h g⁻¹ reversibly at a 200 mA g⁻¹ rate in the voltage range between 3.0 and 0.001 V. The high reversible capacity is retained at elevated current densities. At a current rate as high as 1000 mA g⁻¹, the Co₃O₄/graphene anode can deliver more than 550 mA h g ⁻¹, which is significantly higher than the capacity of current commercial graphite anodes. The superior electrochemical performance of the Co₃O₄/graphene is attributed to its unique nanostructure, which intimately combines the conductive graphene network with uniformly dispersed nano Co₃O₄ particles.     

Pseudocapacitive properties of electrodeposited porous nanowall Co3O4 film

A porous nanowall Co₃O₄ film is prepared by a facile cathodic electrodeposition. The as-prepared porous nanowall Co₃O₄ film shows a net-like porous structure with huge porosity. The porous network is made up of free standing interconnected Co₃O₄ nanoflakes with a thickness of 20 nm. As cathode material for pseudocapacitors, porous nanowall Co₃O₄ film exhibits weaker polarization, higher electrochemical reactivity and better cycling performance as compared to the dense Co₃O₄ film. The specific capacitance of porous nanowall Co₃O₄ film is 325 F g⁻¹ at 2 A g⁻¹ and 247 F g⁻¹ at 40 A g⁻¹, respectively, much higher than that of the dense Co₃O₄ film (230 F g⁻¹ at 2 A g⁻¹ and 167 F g⁻¹ at 40 A g⁻¹). The better pseudocapacitive performances of the porous nanowall Co₃O₄ film are attributed to its highly porous morphology, which provides large reaction surface and short ion diffusion paths, and relaxes the volume change caused by the reaction during the cycling process.     

Metal ions induced dielectric and magnetic loss in Co3O4 for electromagnetic wave absorption

Despite Co₃O₄ has been widely applied in electromagnetic wave (EMW) absorbers, single Co₃O₄ doesn't have excellent EMW absorbing performance. Modification of Co₃O₄ with other metal ions addition is an effective way to improve its impedance matching and EMW attenuation. Herein, CuO/Cu_0.3Co_2.7O₄/Co₃O₄ and NiCo₂O₄/Co₃O₄ composites have been obtained via a facile two-stage strategy, and the influence of Cu²⁺ and Ni²⁺ on the high-frequency and low-frequency EMW absorbing performance of the composites has been investigated as well. The electromagnetic parameters of samples are regulated by adding different metal ions to achieve optimum impedance matching. Dipole polarization and magnetic resonance are the main loss mechanisms. The composite with Cu²⁺ and Ni²⁺ additions exhibits the best EMW absorption with an effective absorption bandwidth (EAB) of 10.8–18.0 GHz for 2.1 mm thickness at high-frequency and 4.5–8.5 GHz for 4.9 mm thickness at low frequencies, respectively. This work offers an effective method for preparing composite materials with multicomponent broadband absorption of oxides.     

Unique porous yolk-shell structured Co3O4 anode for high performance lithium ion batteries

This paper introduces a unique porous yolk-shell structured Co₃O₄ microball, which is synthesized by spray pyrolysis from precursor solution with polyvinylpyrrolidone (PVP) additive. PVP acts as an organic template in the pyrolytic reaction facilitating the formation of yolk-shell structure. The electrochemical properties of porous yolk-shell Co₃O₄ microballs evaluated as anode materials for lithium ion batteries exhibit high initial columbic efficiency of 77.9% and high reversible capacity of 1025 mAh g⁻¹ with capacity retention of 98.8% after 150 cycles at 1 A g⁻¹. In contrast, the hollow microballs obtained without PVP addition show obvious capacity decay from 1033 to 748 mAh g⁻¹ after 150 cycles with the capacity retention of 72.3%. In addition, the microballs with porous yolk-shell structure exhibit better rate performance. The superior electrochemical performance is mainly attributed to the unique porous yolk-shell structure which provides large voids to buffer volume expansion and enlarge the contact area with the electrolyte, shortening the diffusion path of the lithium ions.     

High-performance inductive couplers based on novel Ce3+ and Co2+ ions co-doped Ni-Zn ferrites

High-performance inductive couplers require Ni-Zn ferrites of high saturation magnetization, Curie temperature, permeability and application frequency. However, for inductive couplers some of these properties run against each other in one ferrite. To balance these requirements, in this work, novel Ni-Zn ferrite ceramics co-doped by Ce³⁺ and Co²⁺ ions with chemical formula Ni_0.4Zn_0.5Co_0.1Ce_xFe_2-xO₄ (x = 0–0.06) were designed and fabricated by a molten salt method. For the acquired ferrites, both Ce³⁺ and Co²⁺ ions could come into the lattices. The initially doped Co²⁺ ions would cause a slightly decreased grain size and dramatically reduced the specimen densification, but the further added Ce³⁺ ions could effectively inhibit the density reduction, while the grain size continues to dwindle. The additional Ce³⁺ ions would generate a foreign CeO₂ phase in the acquired specimens. The sole doping of Co²⁺ ions would aggrandize the saturation magnetization of ferrites, but the introduction of Ce³⁺ ions would cause its decrease. However, with an appropriate doping level, the Ce³⁺ and Co²⁺ ions co-doped ferrites could preserve a relatively high saturation magnetization, while the Curie temperature and cut-off frequency of the ferrites are dramatically augmented, although the permeability would be somewhat reduced. The as-acquired ferrites were simulated to apply in inductive couplers, revealing that the devices manufactured by the Ni_0.4Zn_0.5Co_0.1Ce_xFe_2-xO₄ ferrites had significantly high maximum operating frequency, compared with that of the one manufactured by pure Ni_0.5Zn_0.5Fe₂O₄ ferrite.     

Preparation of scale-like nickel cobaltite nanosheets assembled on nitrogen-doped reduced graphene oxide for high-performance supercapacitors

Ultrathin scale-like nickel cobaltite (NiCo₂O₄) nanosheets supported on nitrogen-doped reduced graphene oxide (N-rGO) are successfully synthesized through a facile co-precipitation of Ni²⁺ and Co²⁺ in the presence of sodium citrate and hexamethylenetetramine and subsequent calcination treatment. The composition and morphology of NiCo₂O₄ nanosheets@nitrogen-doped reduced graphene oxide (denoted as NiCo₂O₄ NSs@N-rGO) were characterized by Scanning electron microscope, Transmission electron microscope, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller and thermogravimetric analysis. The thickness of NiCo₂O₄ nanosheets anchored on the reduced graphene oxide is around 4 nm. The capacitance of NiCo₂O₄ NSs@N-rGO is evaluated by cyclic voltammogram and galvanostatic charge/discharge with the result that the NiCo₂O₄ NSs@N-rGO could deliver a specific capacitance of 1540 F g⁻¹ after 1000 cycles at 10 A g⁻¹.     

An improved Hummers method for eco-friendly synthesis of graphene oxide

An improved Hummers method without using NaNO₃ can produce graphene oxide nearly the same to that prepared by conventional Hummers method. This modification does not decrease the yield of product, eliminating the evolution of NO₂/N₂O₄ toxic gasses and simplifying the disposal of waste water because of the inexistence of Na⁺ and NO₃⁻ ions. For the first time, we also developed a prototype method of post-treating the waste water collected from the systems of synthesizing and purifying graphene oxide. The content of Mn²⁺ ions in the purified waste water was measured to be lower than the guideline value for drinking water.     

Holey graphene interpenetrating networks for boosting high-capacitive Co3O4 electrodes via an electrophoretic deposition process

A composite of Co₃O₄/holey graphene (Co₃O₄/HG) was prepared via a facile hydrothermal route, and was then processed into an electrode by an electrophoretic deposition process. Holey graphene (HG) wrapped Co₃O₄ to form a 3D skeleton network, thereby providing high electrical conductivity, and the holes in HG could further shorten the electrolyte ion diffusion pathway. Therefore, by adjusting the mass ratio of Co₃O₄ to HG, the Co₃O₄/HG composite afforded an enhanced capacitance of 2714 F g⁻¹ (at a current density of 1 A g⁻¹), which is 20 times higher than that of pure Co₃O₄. To further explore the practical applications of Co₃O₄/HG, a symmetric supercapacitor employing Co₃O₄/HG was fabricated. The supercapacitor functioned stably at potentials up to 1.2 V, with an enhanced energy density of 165 Wh kg⁻¹ and a high power density of 0.6 kW kg⁻¹ at 1 A g⁻¹.     

Effect of Bismuth substitution on the enhancement of thermoelectric power factor of nanostructured BixCo3-xO4

Bismuth Cobalt Oxide (Bi_xCo_3-xO₄) nanoparticles with different compositions (x?=?0, 0.025, 0.05, 0.1, 0.2) were prepared by chemical precipitation method. The structural, morphological and thermal properties of the prepared samples were studied by XRD, SEM, FTIR and TG&DTA analysis. X-ray diffraction analysis shows that pure phase of Cobalt oxide was formed till x?≤?0.05 and while increasing the Bi concentration (0.05?≤ x?≤?0.2) mixed phases of Co₃O₄, Co₂O₃, CoO and separate phase of Bi₂O₃ were formed. The diffraction peaks were reasonably shifted due to substitution of Bi²⁺ ions. XPS analysis conforms the presence of mixed valance states of Co and presence of Bi with their binding states in the samples. The electrical resistivity and Seebeck coefficient were measured for Bi_xCo_3-xO₄ (0?≤ x?≤?0.2) at different temperatures. It was observed that the electrical resistivity decrease till x?≤?0.05 due to the substitution of Bi ions in Cobalt lattice and increases at higher x values (0.05?≤ x?≤?0.2) due to the formation of Bi₂O₃ phase. The Bi substitution has considerably reduced the electrical resistivity by one order when completely dissolved in the cobalt oxide lattice at lower x values. The Seebeck coefficient value gradually increased for all samples of Bi_xCo_3-xO₄ (0?≤ x?≤?0.2). The power factor was calculated from electrical resistivity and Seebeck coefficient and the maximum power factor of 0.025 µWm^?1K^?2 was obtained for Bi_0.2Co_2.8O₄ sample at 530?K. The experimental results revealed that the Bi substitution have promising effect on the thermoelectric properties of nanostructured Bi_xCo_3-xO₄ (0?≤ x?≤?0.2).     

Ni0.3Co2.7O4 spinel particles/polypyrrole composite electrode:: Study by X-ray photoelectron spectroscopy

In this work we have studied the multilayered polypyrrole/oxide composite electrode on glassy carbon having the structure GC/PPy/PPy(Ni_0.3Co_2.7O₄)/PPy, in which the spinel oxide Ni_0.3Co_2.7O₄ is known to be an electrocatalyst of the oxygen reduction reaction in alkaline medium. The successive GC/PPy, GC/PPy/PPy(Ni_0.3Co_2.7O₄) and GC/PPy/PPy(Ni_0.3Co_2.7O₄)/PPy parts of the electrode were examined by X-ray photoelectron spectroscopy. The results indicate that the electronic structure of the PPy is independent of the thickness of the PPy used to prepare the electrodes. The XPS data also show that cobalt is present in both divalent and trivalent states. The PPy doping degree by Cl⁻ ions (in terms of the Cl⁻/N) and the oxide/PPy mass ratio observed by XPS were 19 and 4.5%, respectively.     

Oxidation of ketones over metal oxide catalysts: I. Catalytic synthesis of biacetyl from methyl ethyl ketone

The gas-phase oxidation of methyl ethyl ketone was studied on metal oxide catalysts in the presence of water vapor. Two types of competitive partial oxidations, i.e., biacetyl formation and oxidative scission reaction leading to acetaldehyde and acetic acid, took place on every oxide studied at 400–500 K. An approximate linear relationship was observed between the selectivity of each reaction and the acid-base property of the oxides; the former reaction was accelerated on the basic oxides such as Co₃O₄, while the latter reaction became predominant on the acidic oxides. As Co₃O₄ was the most effective biacetyl former of single-component oxides, modification of Co₃O₄ was examined to develop more effective catalysts for biacetyl synthesis. Scission reaction took the place of biacetyl formation over a catalyst where Co²⁺ ions were located in Y zeolite by an ion-exchanged method. Scission reaction was suppressed when Co oxide was supported on basic oxides such as MgO or CaO; however, the selectivity to biacetyl was slightly decreased due to the occurrence of a new reaction, acetone formation. The addition of Na₂O or Li₂O to Co₃O₄ was found to improve the selectivity to biacetyl without loss of catalytic activity. The maximum efficiency (13%) in biacetyl formation was attained at a Li content of ca. 7 at.%.