Co3O4 Content Research Articles

Cobalt oxide-alumina catalysts for the methane-assisted selective catalytic reduction of SO2 to sulfur

Preventing emission of pollutants in any kind, is a way to protect global environment. The objective of this study is to develop cobalt catalysts supported on alumina for the conversion of the toxic gas SO2 into elemental sulfur using methane. Although several useful catalysts have been proposed, there is still a need to synthesize a catalyst with a high sulfur yield that is also persistent during on-stream stability. To this end, four different catalysts were prepared using the wet impregnation technique, with Co3O4 content ranging from 0 to 15 wt%. Catalytic activity tests were carried out at atmospheric pressure and temperatures ranging from 550 to 800 °C. The Al2O3–Co (15 %) catalyst exhibited superior performance, with a sulfur yield of 98.1 % at 750 °C. The catalytic stability of the best catalyst was examined using a 20 h on-stream stability test under the optimized conditions including an SO2/CH4 molar feed ratio of 2 at 750 °C. The structural changes of the used catalyst after the stability test were investigated using XRD and TPO analyses. It was revealed that sulfidation of Co3O4 after a short while, results in decreasing the sulfur yield from 98.1 % to 89.8 %.

Evaluation of structural, morphological and optical properties of Co3O4/SnO2 nano-composite films

Nano-composite films of cobalt (II·III) oxide/tin (IV) oxide (Co3O4/SnO2) to be applicable for optoelectronic applications were prepared via sol gel method with variable concentrations of the Co3O4 in the range of 0–45 mol %. Structural analysis using x-ray diffraction (XRD)of the composite powder Co3O4/SnO2 revealed that a polycrystalline structure was formed, whereas the composite films showed an amorphous behavior. Transmission electron microscope (TEM) was performed to investigate the polycrystalline structure of the prepared films. The results obtained from optical measurements indicated that the absorption edge was shifted towards longer wavelengths upon increasing the Co3O4 content from 0 to 35 mol %. Further increase of Co3O4, revealed that the cut off transmission spectra were shifted to higher energies. The refractive index of prepared films increases from 1.61to1.892 along with increasing the Co3O4 mole %. The Co3O4/SnO2 content ratio can control the optical properties and energy band gap of the mixture consequently, the present study is an innovative, promising, and appreciating the Co3O4/SnO2 based composite for optical applications.

Nanocomposite Co3O4-ZnO Thin Films for Photoconductivity Sensors.

Thin nanocomposite films based on zinc oxide (ZnO) added with cobalt oxide (Co3O4) were synthesized by solid-phase pyrolysis. According to XRD, the films consist of a ZnO wurtzite phase and a cubic structure of Co3O4 spinel. The crystallite sizes in the films increased from 18 nm to 24 nm with growing annealing temperature and Co3O4 concentration. Optical and X-ray photoelectron spectroscopy data revealed that enhancing the Co3O4 concentration leads to a change in the optical absorption spectrum and the appearance of allowed transitions in the material. Electrophysical measurements showed that Co3O4-ZnO films have a resistivity up to 3 × 104 Ohm∙cm and a semiconductor conductivity close to intrinsic. With advancing the Co3O4 concentration, the mobility of the charge carriers was found to increase by almost four times. The photosensors based on the 10Co-90Zn film exhibited a maximum normalized photoresponse when exposed to radiation with wavelengths of 400 nm and 660 nm. It was found that the same film has a minimum response time of ca. 26.2 ms upon exposure to radiation of 660 nm wavelength. The photosensors based on the 3Co-97Zn film have a minimum response time of ca. 58.3 ms versus the radiation of 400 nm wavelength. Thus, the Co3O4 content was found to be an effective impurity to tune the photosensitivity of radiation sensors based on Co3O4-ZnO films in the wavelength range of 400-660 nm.

Comparison effect of thin microrod‐nanowhisker manganese oxide (MnO2) and spherical grain‐like cobalt oxide (Co3O4) as nanofiller for performance‐enhanced composite gel terpolymer electrolyte‐based dye‐sensitized solar cells

AbstractGel polymer electrolyte (GPE) are better replacement of liquid electrolyte for dye‐sensitized solar cell (DSSC) but they have low efficiency due to insufficient segmental motion within the electrolyte. By incorporating transition metal oxide nanofiller, it can improve the performance of DSSC due to the existence of cross‐linking center that provides interaction with polymer side chain and redox mediator. Two different transition metal oxides (namely, manganese oxide, MnO2 and cobalt oxide, Co3O4) were synthesized using sonochemical method and incorporated as nanofiller. Poly (vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate) (P(VB‐co‐VA‐co‐VAc)) as a host terpolymer and sodium iodide (NaI) as a dopant salt were used to formulate the composite gel terpolymer electrolytes (CGPEs). The two different shapes of nanofiller have impacted the performance of CGPE proven by the structural analysis. It was found that both systems, the highest ionic conductivity achieved at 2.5 wt% of MnO2 and Co3O4 content with values of 6.40 and 5.2 mS cm−1, respectively. Surprisingly, the performance DSSC of Co3O4‐based CGPE was higher due to the strong Lewis's acidity of Co3O4, which absorb more iodide ions into the surface and facilitating the ions mobility. CGPE containing 2.5 wt% Co3O4 yield the highest efficiency, with value of 3.69%.

Preparation and Electrochemical Performance of Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub>/Co<sub>3</sub>O<sub>4</sub> Composite as an Anode of Lithium-Ion Battery

The Li4Ti5O12/Co3O4 composites were prepared by hydrothermal reaction method with different Co3O4 mass content (3%, 7%, 11%, and 15%). The Li4Ti5O12 nanoparticles were set in-situ on the Co3O4 sheet. Co ion was doped into the Li4Ti5O12 lattice. The first cycle specific capacity firstly increased and then decreased with Co3O4 content increasing, which the discharge capacity reached the peaking value that the first capacity was 1111 mAh/g and the specific discharge capacity retained 240 mAh/g after 200 cycles. After 200 cycles of charge and discharge, the retention of the capacity was 96.4% at 0.1 A/g, and the retention of the capacity was 98.4% at 0.5 A/g.

Role of cobalt precursors in the synthesis of Co3O4 hierarchical nanostructures toward the development of cobalt‐based functional electrocatalysts for bifunctional water splitting in alkaline and acidic media

AbstractThe precursors have significant influence on the catalytic activity of nonprecious electrocatalysts for effective water splitting. Herein, we report active electrocatalysts based on cobalt oxide (Co3O4) hierarchical nanostructures derived from four different precursors of cobalt (acetate, nitrate, chloride, and sulfate salts) using the low‐temperature aqueous chemical growth method. It has been found that the effect of precursor on the morphology of nanostructured material depends on the synthetic method. The Co3O4 nanostructures exhibited cubic phase derived from these four precursors. The Co3O4 nanostructures obtained from chloride precursor have demonstrated improved oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to other precursors due relatively higher content of Co3O4 nanostructures at the surface of material. An overpotential of 400 mV versus reversible hydrogen electrode (RHE) at 10 mA cm−2 was observed for HER. The Co3O4 nanostructures derived from the chloride precursor have shown favorable reaction kinetics via 34 mV dec−1 value of the Tafel slope for HER reaction. The Co3O4 nanostructures derived from chloride precursor have also shown an excellent HER durability for 15 hr in alkaline media. Furthermore, the OER functional characterization was carried out onto Co3O4 nanostructures derived from chloride precursor exhibited 220 mV overpotential at 10 mA cm−2 and Tafel slope of 56 mV dec−1. Importantly, the reason behind the favorable catalytic activity of Co3O4 nanostructures derived from chloride precursor was linked to one order of magnitude smaller charge transfer resistance and higher amount of Co3O4 content at the surface of nanostructures than the Co3O4 nanostructures derived from other precursors. The performance of Co3O4 nanostructures derived from chloride precursor via the wet chemical method suggests that cobalt chloride precursor could be of great interest for the development of efficient, stable, nonprecious, and environmentally friendly electrocatalysts for the chemical energy conversion and storage devices.

Effect of Co3O4 on the structure and electrochemical performance of IrO2-Co3O4/Ti electrodes by first-principles calculations and experimental

The electrode materials have a decisive effect on the performance of supercapacitors. IrO2-Co3O4/Ti composite material was prepared by a thermal decomposition method. The first-principles calculation was used to study the effect of Co content on the electronic structure of IrO2-Co3O4. The influence of the Co3O4 content on the microstructure and electrochemical performance of the electrode was analyzed in detail. First-principles calculation revealed that the coating with the 50% mol Co3O4 was in a full conductive structure, and the density of states of the composite oxide with excessive content of Co3O4 would shift to a higher energy level and generate a band gap. Co doping could inhibit the crystallization of IrO2. The 50%IrO2-50%Co3O4/Ti electrode exhibited the most obvious coexistence of crystalline and amorphous phases. Besides, the addition of Co3O4 changed the microstructure to a ring-shaped branched structure, which effectively increased the specific surface area and total pore volumes of the coating. The electrode with the 50% Co3O4 had the maximum capacitance value of 979.6 F/g and maintained 90% of its initial capacitance even after 20,000 cycles of constant charge-discharge cycles, which was an ideal electrode material for supercapacitors. The results from first-principles calculation and the experiments were in consistency.

Enhanced the electrochemical performance of mesh nano composite based catalyst for oxygen evolution reaction: Recent development

The energy crisis globally has severely damaged the economy of the globe which forces researchers and scientists to provide a new promising technology. Also, the rapid depletion of fossil fuels leads to an energy crisis & environmental concern, because of this, economic stress is created for the people of the world. To overcome these, water splitting is sustainable and renewable energy, but it requires active electrocatalysts. The nanostructure material morphology characterization was investigated by the, XRD, EDS, SEM, HRTEM, EELS chemical composition maps through & XPS which properly reveal the nanocomposite materials morphology strongly aggregates. The materials exhibit outstanding OER response as compared to Co3O4 & manganese sulfide due to the synergetic effect produced in the composite materials including fast charge transport from MoSOX, active sites & high density of Co3O4, which accelerates the OER kinetics. Between the composites, Co3O4-MoSOX with the greatest amount of Co3O4 (S4 0.7g) content owns the lower overpotential to produce OER kinetics & having a 60 mV dec−1 and Tafel slope of as compared to other material. Further, for the exchange of current density of 2.97 × 10−3A/cm2 & it is extremely durable for 45 h. The EIS ensure the fast charge transport for the extra addition of pristine S4 (0.7g) in the composite, which potentially enhanced the production of the OER kinetics activity. In this regard transition metal oxide especially, Co3O4 is promising material, but it requires certain strategies to improve its catalytic kinetics activity & stability for the full water splitting. Keeping these challenges, the proposed study is of great concern to economical and societal needs, which can lead to a boost in the electrochemical applications in particular oxygen evolution reaction (OER). Therefore, rapid efforts must be made to realize the nonprecious catalysts for water splitting and equality compete with the world in the hydrogen/electron economy.

Enhanced thermal and dielectric performance in ternary PVDF/PVP/Co3O4 nanocomposites

AbstractThe main objective of this research was to prepare high thermal and dielectric performance PVDF/PVP/Co3O4 nanocomposites (PVDF, oply(vinylidene fluoride); PVP, polyvinylpyrrolidone) using the method of solution mixing. The structural properties and thermal stability of the samples were examined through measurements of XRD, SEM, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). From the XRD measurements, the cubic crystal structure of the Co3O4 nanoparticles was revealed with an average size of 17 nm. Also, diffraction peaks of the α‐phase were seen in PVDF/PVP/Co3O4 nanocomposite spectra. The SEM images for the surface of the films showed a homogeneous distribution of the nanoparticles. The absorption peaks of both α‐ and β‐phases were confirmed by measurements of the FTIR spectra. The nanocomposite films grafted with Co3O4 nanoparticles possess high thermal stability. The dielectric permittivity and energy density of the nanocomposites improved significantly at 4.0 wt% Co3O4. Finally, the increase in Co3O4 content caused an improvement in dielectric response function as well as electrical conductivity. © 2021 Society of Industrial Chemistry.

Development of Mn-Zn power ferrite with low losses over a broad temperature range for applications in the high frequency region of 0.5-3 MHz

Due to the rapid development of electronic devices towards high frequency, miniaturization, and high efficiency, it is imperative to develop MHz-frequency power ferrites exhibiting low loss over a broad temperature range. In this work, the broad-temperature low-loss Mn-Zn power ferrites operating in the frequency range of 0.5-3 MHz have been fabricated following the traditional oxide ceramic process. Co3O4 was added and its content was optimized to achieve the broad-temperature characteristics of power loss. The optimal Co3O4 content was determined to be 0.35 wt%. The power losses of this material are less than 30, 120, and 30 kW/m3 in the broad temperature range from 0 to 120 °C under the conditions of 500kHz/50 mT, 1MHz/50 mT, and 3MHz/10 mT, respectively. This material is an ideal material for applications in power conversion electronics at high frequencies (0.5-3 MHz). The effect of Co3O4 addition on power loss is discussed based on the compensation model of magnetocrystalline anisotropy constant. Analysis of the three parts of power loss reveals that the residual loss gradually becomes to be predominant above 1.2 MHz. The addition of Co3O4 reduces the residual loss and increases the cut-off frequency. This is ascribed to the induced uniaxial anisotropy of Co2+.

Embedding Co3O4 nanoparticles in three-dimensionally ordered macro-/mesoporous TiO2 for Li-ion hybrid capacitor

Lithium-ion hybrid capacitors (LICs) have gained increasing focus owing to their high energy/power densities. The development of anodes with superior rate capability is an effective way to surmount the kinetic mismatch between anodes and cathodes, and thus, enhancing the energy/power densities. Herein, Co3O4 nanoparticles embedded in three-dimensionally (3D) ordered macro-/mesoporous TiO2 (Co3O4@TiO2) are synthesized through an in situ method from dual templates. Differing from the composite prepared by loading active nanoparticles on support, Co3O4 nanoparticles are embedded in TiO2 framework, which can improve the stability of the electrode. Furthermore, the hierarchically porous structure of TiO2 is in favor of the rapid diffusion of ions and electrolyte. As a result, The Co3O4@TiO2-2 composite with an optimized Co3O4 content (~25 wt%) delivers a high capacity of 944.1 mAh g−1 after 100 cycles at 0.1 A g−1 and high-rate capability (405.7 mAh g−1 after 1000 cycles at 5 A g−1). The LIC assembled with Co3O4@TiO2-2 anode and activated carbon (AC) cathode delivers high energy/power densities (maximum, 87.9 Wh kg−1/10208.9 W kg−1) and great cycle stability (88.1%, 6000 cycles, 0.5 A g−1).

Dielectric properties and AC conductivity of PIn and PIn/Co3O4 composites

Polyindole/Co3O4 composites have been synthesized by chemical-oxidative-polymerization route with APS as an oxidizer. The composites were made by mixing them in the well defined proportions, PIn1-x(Co3O4)x; x = 0.1, 0.2, 0.3, 0.4 and 0.5. XRD scans of the samples revealed their amorphous nature. The dielectric measurements were carried out over wide frequency and temperature. Dielectric constant and loss were found to decrease with frequency and increase with temperature. AC conductivity is found to decrease by an order of magnitude with increase of Co3O4 content. By fitting Arrhenius expression to conductivity, its activation energy has been determined to lie in the range 0.19 meV to 4.52 meV. Activation energy decreased with increase in the quantity of Co3O4.

High CO reactivity of cobalt oxide catalyst deposited on alumina powders by rotary chemical vapor deposition

Cobalt oxide (Co3O4) catalysts supported on α-Al2O3 were prepared by a rotary chemical vapor deposition (CVD) method. Although the specific surface area of α-Al2O3 powders was extremely low, finely dispersed nanoparticles of Co3O4 with the size of several nanometers were formed on the support under the deposition condition of 370 °C for 30–120 min. Despite the minimal Co3O4 content of 0.10–0.36 wt%, the Co3O4/α-Al2O3 exhibited the significant catalytic activity for CO oxidation; the temperatures at which the conversion of CO reached 20% (T20) were 157–189 °C and the conversion reached 100% until 300 °C. Thus, a rotary CVD method can finely control the dispersibility of Co3O4 on α-Al2O3 surface, which was related to high catalytic activity.

Facile one-step deposition of Co3O4-MoS2 nanocomposites using a vacuum kinetic spray process for non-enzymatic H2O2 sensing

Co3O4-MoS2 nanocomposites (NCs) were deposited on titanium sheets at room temperature using a vacuum kinetic spray process and Co3O4 and MoS2 micro powders. Co3O4-MoS2 NCs/Ti electrodes were used as electrocatalysts for non-enzymatic detection of H2O2 in 0.1 M NaOH. X-ray photoelectron spectroscopy revealed an improvement in the synergy between various cobalt-based active sites and MoS2 species in all hybrid electrodes. Analysis of the amperometric response of H2O2 oxidation in 0.1 M NaOH revealed that titanium-modified electrodes with either nanostructured Co3O4 or Co3O4-MoS2 NCs exhibited a wide linear detection range of 20 μM to 1mM. A gradual increase in the amount of Co3O4 in the modified electrodes led to a reduction in charge-transfer resistance and the evolution of more electro-active sites at the working electrode surface, accompanied by an overall enhancement in detection sensitivity to a peak of 3000 μA·mM−1·cm−2 at a Co3O4 content of 75 wt.%. Besides, the titanium modified electrodes with Co3O4-MoS2 NCs exhibited high selectivity for H2O2 oxidation in 0.1 M NaOH.

Structural and shielding properties of NiO/xCo3O4 nanocomposites synthesized by microwave irradiation method

In the present study, nanocomposites with different ratios of NiO and Co3O4 (x = 0.3, 0.5, and 0.7) have been prepared via microwave oven and characterized using XRD. FLUKA code has been used to estimate the values of the mass attenuation coefficient (μm) for all samples. From the measurement, we found that when the thickness of the samples increases, the gamma transmission values decrease. Besides, the μm values increase as the Co3O4 content increase from 0.3 to 0.7%. At selected photon energy, the HVL, TVL, and MFP values decrease with increasing Co3O4 concentrations. At low energies (0.1–0.5 MeV), the linear decreasing trend in MAC values indication that photoelectric effect (PEA) (∝1/E3.5) dominance over this region. Afterward, at medium energy regions (0.5–1.33 MeV), the decrements in MAC values are insignificant as the Compton scattering (CS) (∝1/E) phenomenon dominates. As a conclusion, CoNi3 has superior effectiveness as a shielding material.

Encapsulated Co3O4/(SiAl@Al2O3) thermal storage functional catalysts for catalytic combustion of lean methane

It is well known that the structural problem between the autothermal operation and the outside utilization of heat in the catalytic combustion system and the runaway on catalyst bed is hard to avoid during the combustion process. Herein, the encapsulated Co3O4/(SiAl@Al2O3) thermal storage functional catalysts which couple Co3O4 catalysts and SiAl@Al2O3 phase change materials are proposed and firstly applied for catalytic combustion of lean methane to improve the thermal environment of the catalyst bed and achieve the high efficiency of lean methane utilization. The thermal management behaviors of such thermal storage functional catalysts and the dynamic coupling effect between heat storage/release characteristics of catalysts and catalytic performance during methane combustion process are investigated in detail. It is found that the encapsulated Co3O4/(SiAl@Al2O3) thermal storage catalysts retain the high latent heat of SiAl@Al2O3 phase change material (410 J/g) and the values vary from 280 J/g to 30 J/g when the SiAl@Al2O3 content decreases from 90 wt% to 10 wt%. When applying the catalysts to catalytic combustion of lean methane, such thermal storage functional catalysts with high thermal storage density show significant efficiency of lean methane conversion than pure Co3O4, and it can also keep the methane conversion at a high level for a long time even if the external heat source disappears. This indicates that the effective heat management of Co3O4/(SiAl@Al2O3) thermal storage catalysts during methane combustion process plays a crucial role in determining the catalytic activity via improving the thermal runaway and hot spots problems in catalyst bed and reducing heat loss. However, the content of SiAl@Al2O3 needs to be carefully regulated to avoid the decrease of activity resulting from the low active Co3O4 content. Particularly, the Co3O4/(SiAl@Al2O3-30 wt%) catalyst shows a competitive activity (e.g., T10, T50 and T90 at 226, 282 and 370 °C) and it surpasses the activity of pure Co3O4 in literatures although the active Co3O4 content is significantly lower than them. After turning off the heat source for 37 min, its methane conversion can still reach 50%, which is twice that of pure Co3O4. The present approach for thermal management in catalytic methane combustion reaction will provide good references for solving the problems (e.g., temperature runaway and hot-spot) in fixed bed reactors during other complex heterogeneous chemical reactions.

A Highly Stable and Efficient Co–Mg–Sr Mixed Oxide Catalysts for Hydrogen Production from Glycerol Steam Reforming

The production of hydrogen from glycerol steam reforming (GSR) was studied over a series of Co–Mg–Sr (CMS) mixed oxide catalysts. Co-precipitation method was adopted to prepare catalysts by varying the molar ratios of MgO–SrO and keeping Co3O4 content constant. The physico-chemical properties of the samples were investigated by BET surface area, X-ray diffraction, hydrogen chemisorption, temperature programmed reduction, temperature programmed desorption of CO2, Raman spectroscopy and CHNS analysis. The reforming activity depended on the composition of the metal oxides. The catalyst with Co–Mg–Sr molar ratio of 3:1:1 exhibited the highest catalytic activity at 700 °C. Glycerol was completely converted to gaseous products and showed 72% hydrogen yield. Catalytic activity of the catalysts was explained on the basis of cobalt particle size, basicity and metal oxides interaction. The catalysts basicity originating from MgO–SrO is also playing an important role in GSR. The present catalyst activity was unaltered even after 100 h of time on stream analysis.

Co3O4/g-C3N4 Hybrids for Gas-Phase Hg0 Removal at Low Temperature

The Co3O4/g-C3N4 hybrids are constructed via the incipient wetness impregnation method by depositing Co3O4 onto the exterior of g-C3N4, and then employed for Hg0 capture within 60–240 °C. The results show that the Co3O4/g-C3N4 hybrid with a Co3O4 content of 12 wt% performs optimally with the highest Hg0 removal efficiency of ~100% at or above 120 °C. The high performances of the Co3O4/g-C3N4 hybrids are probably attributed to the tight interfacial contact between Co3O4 and g-C3N4, with its improved electron transfer, inferring that cobalt oxide and g-C3N4 display a cooperative effect towards Hg0 removal. NO and SO2 shows a significant suppressive influence on the mercury capture performance, plausibly owing to the competing adsorption and side reactions.

Synergistic effect of hexagonal flake Co3O4@PANI core–shell composites with excellent microwave-absorbing properties

Hexagonal flake Co3O4 was prepared by calcining Co-MOF precursors in air. Co3O4@PANI was obtained via hydrothermal and oxidative polymerization processes, and the electromagnetic wave absorption properties of the composites were investigated. Scanning emission microscopy and transmission electron microscopy images show that hexagonal flake Co3O4 possesses a diameter in the range of 2–4 µm and a side length 550–950 nm. With the decrease in Co3O4 content, the absorption performance of Co3O4@PANI increases gradually. When the mass ratio of Co3O4 to PANI is 1:8, the minimum reflection loss value is − 37.39 dB at 7.28 GHz with a layer thickness of 4 mm. Co3O4@PANI also has effective absorption with the entire test thickness, and the maximum absorption bandwidth can reach 3.52 GHz. Therefore, the as prepared hexagonal flake Co3O4@PANI has potential for application in the field of electromagnetic wave absorption.

Effects of Co3O4 Addition on Friction and Dry Sliding Wear Characteristics of 8 mol% Yttria-Stabilized Cubic Zirconia

The aim of the present study was to investigate the influence of Co3O4 additive on the microstructure, wear, and tribological properties of 8 mol% yttria-stabilized cubic zirconia (8YSZ) using a pin-on-disk tribometer, surface profilometer, hardness tester, and a scanning electron microscopy system. Specimens were produced by doping 1-15 wt.% Co3O4 in 8YSZ using a colloidal process, sintering at 1500 °C for 1 h, and subsequent annealing at 1500 °C for 10 and 50 h. Microstructural analysis showed that Co3O4 dissolved partially in 8YSZ, with the undissolved Co3O4 precipitating as a secondary phase at the grain boundaries. Further, the addition of Co3O4 enhanced the grain size. Wear tests were carried out using an Al2O3 ball as the counterface against ceramic disk under dry sliding friction conditions at room temperature (24 °C). The wear volume of 8YSZ decreased from 0.30 to 0.11 mm3 as a result of the addition of 15 wt.% Co3O4. Additionally, friction coefficient of the 8YSZ significantly reduced from 0.55 to 0.17 at the beginning stage of the sliding after the addition of 15 wt.% Co3O4. This was because Co3O4 creates a thin lubricating layer on the friction surface. In addition, the undoped and Co3O4-doped 8YSZ specimens exhibited abrasive wear under the dry sliding friction conditions, owing to the formation and propagation of microcracks, which resulted in the removal of material from the surface. The specific wear rate of 8YSZ decreased with increasing the Co3O4 content. Thus, the addition of Co3O4 to 8YSZ improves its wear resistance and surface topography.