Porous Co3O4 Research Articles

Metal-organic framework derived porous nanosheets-like Co3O4 electrodes on stainless steel with high-performance for supercapacitors

In this work, three-dimensional (3D) nanoporous MOF-derived Co3O4 was successfully prepared by a facile, easy, and rapid solvothermal method on a stainless steel substrate using 1, 4-BDC organic linker and a precursor. Additionally, the effects of the Co-precursor and organic linker on the structure, composition, and morphology of the prepared MOF-derived Co3O4 samples were investigated through an XRD study, which indicated that the MOF-derived Co3O4 thin films exhibited crystalline nature upon deposition on the stainless steel substrate. FE-SEM revealed a porous nanosheet-like morphology. EDAX analysis confirmed the formation of the MOF-derived Co3O4 structure, indicating the presence of cobalt, oxygen, and carbon elements. The oxidation states of the prepared MOF-derived Co3O4 thin films were determined by X-ray photoelectron spectroscopy. Furthermore, the electrochemical performance of the MOF-derived Co3O4 samples was evaluated in a three-electrode system using 1 M KOH electrolyte. Consequently, optimized MOF-derived Co3O4 exhibited excellent electrochemical performance attributed to these advantages. The C3 sample demonstrated an outstanding specific capacitance of 1210 F/g at a current density of 0.5 mA/cm², along with remarkable cyclic stability retention of 94.30 % after 4000 charging/discharging cycles. Additionally, the MOF-derived Co3O4 (C3) electrode showed an excellent energy density of 35.70 Wh/kg and a power density of 4.5 kW/kg. As a result, the unique hierarchical porous structure of MOF-derived Co3O4 also offers effective pathways and excellent electrochemical performance, making it a promising candidate for advanced electrode materials in high-performance supercapacitors.

Chemiresistive detection of xylene vapor using MOF-derived porous Co3O4 microrods activated by Mo6+ cations

Incorporation of high-valence cation into catalytic oxide (eg. Co3O4) is favorable for regulating the carrier concentration and creating more active centers for surface reaction process, thus promoting the sensing capability towards low reactive gas (eg. xylene). Herein, the metal-organic framework (MOF)-derived Mo-doped porous Co3O4 microrods are achieved through a simple solution method combing with a thermal method. The introduction of Mo6+ into Co3O4 matrix enhances the concentration of oxygen defects and Co3+, coupled with the specific surface area. As a result, the 5 at% Mo/Co3O4-based gas sensor sample exhibits a nice selectivity, clear response value (Rg/Ra=29.8 – 100 ppm), low concentration limit (0.5 ppm), and reliable stability to xylene vapor under a low working temperature (140 °C). Moreover, the possible reaction pathway (benzyl-benzaldehyde-benzoate-aromatic ester/anhydride) of xylene oxidation over this 5 at% Mo-doped Co3O4 microrod is proved by an in-situ DRIFTS analysis. Importantly, this optimized xylene-sensing capability is further discussed from the viewpoint of Mo-introducing effect into the porous Co3O4 microrods. This work further demonstrates a reliable approach of high valence cation-doped catalytic oxides to detect low reactive vapor.

Hierarchical ultra-thin porous Co3O4 nanosheets derived from mixed phase α- and β-Co(OH)2 for high sensitivity and ppb-level acetone sensing

Addressing the energy loss of carriers during transmission and achieving high sensitivity detection of target gases facilitates the synthesis of trace-level acetone sensors, which is of great significance in the fields of air quality early warning, health monitoring, and industrial safety monitoring. Here, we propose a strategy where, under hydrothermal conditions, the content of mixed-phase α- and β-Co(OH)2 is regulated by varying the protonation level of 2-methylimidazole in different solutions, leading to the formation of porous monocrystalline Co3O4 microflower structure. The microflower is assembled from ultrathin nanosheets, and the 3D-interconnected macroporous and mesoporous structure provides high surface area and gas diffusion channels. The monocrystalline and two-dimensional structures favor high carrier mobility, enhancing the signal-to-noise ratio. Furthermore, the thickness of the Co3O4 nanosheets is less than twice the Debye length, making their electrical properties completely dependent on surface. DFT calculations also indicate that the few layers Co3O4 model is conducive to acetone adsorption. The Co3O4 sensor exhibits exceptional gas sensing performance towards acetone, with favourable sensitivity (16.83 to 10 ppm), selectivity, and stability, as well as an ultra-low practical detection limit of 10 ppb. Rich point defects and line defects play a significant role in improving the surface activity of the sensitive material as well. This research offers a pathway for designing sensors with exceptional gas sensitivity by employing a straightforward method to control the morphology of sensitive materials, combined with defect engineering to enhance sensing activity.

Two-dimensional confined topotactic transformation to produce Co-Pi/Co3O4 hybrid porous nanosheets for promoted water oxidation

Exploring advanced electrocatalyst for the oxygen evolution reaction (OER) is of great importance in pursuing efficient and sustainable hydrogen production via electrolytic water splitting. Considering the structure–activity-stability relationship for designing advanced OER catalysts, two-dimensional (2D) porous catalyst with single crystallinity is deemed to be an ideal platform which could simultaneously endow enriched active sites, facile mass and charge transport ability as well as robust structural stability. Herein, we proposed a facile 2D confined topotactic phase transformation approach, which realizes the fabrication of highly porous single-crystalline Co3O4 nanosheets with in-situ surface modification of amorphous Co-Pi active species. Benefitted from the highly exposed undercoordinated cobalt sites, facilitated mass transport and facile 2D charge transfer pathway, the Co-Pi/Co3O4 hybrid porous nanosheets display enhanced OER activity with obvious pre-oxidation-induced activation. In addition, the operational stability was significantly improved owing to the strengthened structural stability which effectively buffers the internal strains and avoids the structural collapse during the electrochemical process. This work proposed a facile and mild method for the synthesis of amorphous/single-crystalline hybrid porous materials, and the achievement of synergistic modulation of active site density and charge transfer ability via targeted microstructural construction will shed light on catalyst design in the future.

Efficient mixed-potential acetone sensor with yttria-stabilized zirconia and porous Co3O4 nanofoam sensing electrode for hazardous gas monitoring and breath analysis

For hazardous gas monitoring and non-invasive diagnosis of diabetes using breath analysis, porous foams assembled by Co3O4 nanoparticles were designed as sensing electrode materials to fabricate efficient yttria-stabilized zirconia (YSZ)-based acetone sensors. The sensitivity of the sensors was improved by varying the sintering temperature to regulate the morphology. Compared to other materials sintered at different temperatures, the porous Co3O4 nanofoams sintered at 800 °C exhibited the highest electrochemical catalytic activity during the electrochemical test. The response of the corresponding Co3O4-based sensor to 10 ppm acetone was –77.2 mV and it exhibited fast response and recovery times. Moreover, the fabricated sensor achieved a low detection limit of 0.05 ppm and a high sensitivity of –56 mV/decade in the acetone concentration range of 1–20 ppm. The sensor also exhibited excellent repeatability, acceptable selectivity, good O2/humidity resistance, and long-term stability during continuous measurements for over 30 days. Moreover, the fabricated sensor was used to determine the acetone concentration in the exhaled breaths of patients with diabetic ketosis. The results indicated that it could distinguish between healthy individuals and patients with diabetic ketosis, thereby proving its abilities to diagnose and monitor diabetic ketosis. Based on its excellent sensitivity and exhaled breath measurement results, the developed sensor has broad application prospects.

Facile synthesis of N-doped porous CoO@C nanocubes as anode with superior lithium storage

N-doped porous CoO@C nanocubes were fabricated using a hydrothermal method and annealing process. The uniform wrapped carbon layer effectively mitigates the volume changes during electrochemical reactions. Moreover, the porous carbon layer enhances the electrical conductivity and promotes Li ion diffusion. Therefore, the as-prepared CoO@C nanocubes maintian a capacity of 565 mA h/g at 0.2 A/g after 100 cycles. This stabilization ability is attributed to the introduction of carbon layer and its porous structure, which buffers the volume expansion of cobalt oxide, and increases the surface area and active sites.

Design synthesis of ZnO nanoparticles on Co3O4 nanosheet with rich oxygen vacancies for rapid detection of NO2 at room temperature

The solvothermal and wet chemical method was developed to synthesized the p-n heterostructures of the thin porous Co3O4 nanosheets with ZnO nanoparticles. The resulting products were analyzed by using various characterization techniques. The results possessed that the presence of a large number of oxygen defects on the surface of Co3O4-ZnO-7 favors enhancing the NO2 adsorption. Correspondingly, the formation of p-n heterojunction and the large surface area of the material itself increased the carrier density and exposed more active sites, which collectively boost the sensing performance to NO2. The sensor showed a high response of 45.7 (S = Ra/Rg) to 100 ppm NO2 at room temperature (RT = 25 °C), with a short response/recovery time (1.3/25 s), and the lower detection limit of the sensor reached 30 ppb, with good selectivity, reproducibility and stability. This study will offer the opportunity to develop new sensors with high response and fast response-recovery to NO2 at room temperature.

Unlocking low-concentration NH3 gas sensing: An innovative MOF-derived In2O3/Co3O4 nanocomposite approach

Ammonia (NH3) is an odorless gas with a pungent smell that can affect health differently based on exposure and concentration. In this study, indium oxide was decorated with cobalt oxide (In2O3/Co3O4) flower-like nanocomposites (NFs) as gas-sensitive materials, revealing p-type semiconducting characteristics. The detection of ammonia (NH3) at low concentrations is a significant challenge for chemoresistive gas sensors. Porous Co3O4 nanoflowers were combined with In2O3 nanoparticles to form p-n heterojunctions for NH3 detection. The p-n heterojunction effect and the capability of the sub-valent band to hold vacancies within In2O3 nanoparticles effectively inhibit electron-hole recombination and extend the carrier lifetime. The In2O3/Co3O4 = 0.04 ratio-based gas sensor exhibited excellent selectivity, achieving a low detection limit of 500 ppb for NH3 at 250 °C. The rapid diffusion of gas within the porous Co3O4 NSs and In2O3 nanoparticles accounted for the high response (7.72) and fast response/recovery time (92 s/51 s) of the In2O3/Co3O4-based gas sensor to 10 ppm NH3. This study presents a method for fabricating NH3 gas sensors with trace-level detection capabilities by adjusting the band structure of nanoparticles and three-dimensional metal-oxide nanostructures.

A multi-strategic exploration towards significantly enhanced electrochemical performance of Co3O4-based anodes for lithium-ion batteries

Electroactive cobalt oxide (Co3O4) exhibits great promise as an anode material for lithium-ion batteries (LiBs) owing to its high theoretical capacity. However, its potential application faces challenges posed by low conductivity and poor cycling stability. In this study, a comprehensive multi-strategic approach was employed to fabricate a high-performance Co3O4-based anode. The approach involved utilizing Co–Cu bimetallic metal-organic frameworks (MOFs) anchored on a stainless-steel mesh (SSM) as the precursor. The resulting free-standing anode comprises Cu-doped porous Co3O4 nanosheets, offering several advantageous characteristics such as being binder-free, possessing a hierarchically porous architecture, and demonstrating improved conductivity and structure stability. This combination of merits results in a material that exhibits significantly enhanced electrochemical performance, featuring high specific capacity, excellent cycling stability, and remarkable rate performance. This multi-strategic exploration of metal oxides with tailored surface area and pore size enables the precise design and fabrication of advanced anodes, specifically optimized for the demanding requirements of LiBs.

Facile synthesis of Co3O4 with porous capsule–shaped structure and its lithium storage properties as anode materials for Li–ion batteries

In this work, a porous Co3O4 anode material with capsule–shaped morphology is prepared by a simple solvothermal method and subsequent heat treatment process in air. The as–synthesized CoCO3 precursor and Co3O4 sample are systematically studied and analyzed by a series of testing technologies, such as XRD, FTIR, FESEM, (HR)TEM, TGA, XPS and N2 adsorption/desorption measurement. As negative materials in Li–ion batteries, the Co3O4 active material exhibits high charge/discharge specific capacity, good rate performance and satisfactory cycle stability. The excellent electrochemical properties are inevitably related to the structural characteristics of the electrode material itself, including regular morphology, rich pore structure, large specific surface area, high crystallinity, nanoscale particle size, etc.

Efficient and stable neutral seawater splitting achieved via strong-proton-adsorption in Pd-O-Co collaborative coordination

Direct electrolysis of pH-neutral seawater for hydrogen generation is a promising method for storing renewable energy. However, the oxygen evolution reaction (OER) faces a selectivity challenge, competing with chlorine evolution and confronting severe corrosion issues of the electrode. Here, we have synthesized ultrathin, polycrystalline, porous Co3O4 nanosheets with Pd single atoms (PdSA-Co3O4) for efficient and stable pH-neutral seawater decomposition. The octahedral Pd-O-Co active unit, generated by the synergistic coordination of the Pd single atom strong proton adsorption (SPA) material with Co3O4 nanosheets, resulted in PdSA-Co3O4 have activities 3, 5, and 31 times higher than Co3O4, IrO2, and commercial Co3O4, respectively. It also remained stable in pH-neutral seawater for 80 h. Operando in situ Raman spectroscopy combined with density functional theory calculations showed that synergistic interactions between the strong proton adsorption of Pd single atoms and the active site Co enhanced the adsorption of intermediates and significantly reduced the free energy of adsorption at the rate-determining step (O*→OOH*). The Pd-O-Co active units inhibited the transformation of the dynamic structure of the Co3O4 substrate and reduced the corrosive effect of Cl ions during the OER process.

Highly-enhanced toluene gas-sensing behavior of high-valent metal-cations doped Co3O4 nanostructures derived from ZIF-67 MOF

In this paper, the different valent metal-cations (Zn2+, In3+ and Zr4+) doped porous Co3O4 nanostructures were synthesized through the pyrolysis of ZIF-67 metal–organic framework (MOF). The influence of the different valence and doping content of metal-cations on the morphology, microstructures and gas-sensing performance of Co3O4 sensors is discussed in detail. The Zr-doped Co3O4 nanostructures present the higher specific surface area for the smaller average grain size, and the toluene gas-sensing performance of Co3O4 nanostructures is significantly improved with the high-valent Zr-doping. The high valence Zr-doping greatly improves the toluene gas-sensing properties, which Co2.717Zr0.189O4 sensor exhibits the highest response value of 94.58 to 100 ppm toluene gas (3.8-fold of Co3O4 sensor). The donor Zr-doping to p-type Co3O4 nanostructures optimizes the hole distribution and further affects Fermi level. Combining with the more oxygen adsorption from the high specific surface area, the resistance in air greatly decreases and resistance in toluene gas increases.

Fabrication of one-dimensional porous p-type Co3O4 rods-based sensors for ultra-high sensitivity and selectivity towards benzene vapour

This study reports on the noble gas sensing properties of Co3O4 nanostructures for the detection of benzene vapour at a low functional temperature of 75 ˚C. The Co3O4 nanostructures were synthesized hydrothermally at different reaction temperatures ranging from 120 ˚C to 220 ˚C. Surface morphology analysis of the nanostructures revealed the formation of 1-D mesoporous nanorods at lower reaction temperatures, i.e., 120 ˚C and 140 ˚C, while synthesis at higher temperatures disintegrated the nanorods and formation of agglomerated plate-like and block-like nanostructures was observed. Among the Co3O4 nanostructures, 1-D nanorods synthesized at 140 ˚C demonstrated a notable response of 361 towards 5 ppm benzene at 75 ˚C. In addition, the lowest theoretical detection limit of 1.9 ppb and sensitivity of 92 ppm−1 were observed for 1-D mesoporous nanorods. The reported ultra-sensitivity of the 1-D mesoporous nanorods is attributed to the porous surface that supplied numerous sites for adsorption/desorption of O2- ions and benzene molecules, the rod-like configuration of its crystallites that provided connecting pathways for efficient charge transportation and the catalytic oxidation of Co3O4 to benzene. Further analyses of the long-term stability of the sensor stored for 304 days and tested in dry air and under relative humidity were discussed in detail as well as the sensing mechanism induced by surface oxygen and benzene gas adsorption.

Effect of Precursor and Calcination Time on the Morphological Structure and Catalytic Activity of Co3O4 Film in the Oxygen Evolution Reaction

This research investigates the effect of cobalt precursor and calcination time on the morphology and catalytic activity of Co3O4 films in the oxygen evolution reaction (OER). Co3O4 films with porous flower-like nanostructures were obtained using cobalt nitrate as a cobalt precursor, while cobalt chlorides were used to produce porous nanoneedle structures Co3O4 film. Extended annealing time at temperatures 350°C caused structural fractures in the films. Among the samples, the synthesized Co3O4 films were then evaluated as catalyst materials for the OER in alkaline 1M KOH electrolyte. Among synthesized films, the Co3O4-2-1h, synthesized using the cobalt chlorides as Co precursor and annealed at 350°C for 1 hour, exhibited better OER catalytic activity. With its porous nanoneedle structure, the Co3O4-2-1h demonstrated superior performance comparable to the state-of-the-art 20% Ir/C catalyst. Moreover, the Co3O4-2-1h film demonstrates remarkable stability for the OER in a 1M KOH alkaline electrolyte.

Enhanced Electrochemical Performance of Low-Content Graphene Oxide in Porous Co3O4 Microsheets for Dual Applications of Lithium-Ion Battery Anode and Lithium-Ion Capacitor

Enhanced Electrochemical Performance of Low-Content Graphene Oxide in Porous Co3O4 Microsheets for Dual Applications of Lithium-Ion Battery Anode and Lithium-Ion Capacitor

Mo-doped porous Co3O4 nanoflakes as an electrode with the enhanced capacitive contribution for asymmetric supercapacitor application

Cobalt oxide (Co3O4) electrode materials have tremendous properties for supercapacitors, such as being environmentally friendly, having a high surface area, being low cost, and having high theoretical specific capacitance (3560 Fg−1). However, its poor electronic conductivity restricts the performance of the practical application. Doping transition metal ions into the host materials is an effective method to improve conductivity and enhance storage capacity. In this research work, we studied Mo-doped Co3O4 nanostructure electrodes synthesized using the electrodeposition technique. The integrated material samples were characterized by XRD, SEM with EDAX, XPS, FTIR, Raman spectra, UV–visible, and BET for their structure, morphology, composition, optical, and surface area properties. The 2 mM Mo-doped Co3O4 electrode exhibits excellent electrochemical pseudocapacitive properties. The optimized Mo2-doped Co3O4 shows a maximum specific capacitance of 1674 Fg−1 at 10 mA cm−2 current density in 1 M KOH electrolyte solution. Finally, the asymmetrical hybrid supercapacitor device (AsHScD) Mo2-Co3O4//rGO) demonstrates the highest power density of 159.0 KWKg−1 and maximum energy density of 13.80 WhKg−1 with a long-term stability of 95 % up to 2000 cycles. The Mo2-Co3O4 electrode is a promising candidate material for a charge-storage hybrid supercapacitor in an aqueous 1 M KOH electrolyte.

Enhanced CO oxidation in porous metal-oxide nanoparticles derived from MOFs

Porous nanoparticles of Co3O4, Fe2O3 and Fe3O4 were successfully developed. Among them, the porous Co3O4 nanoparticles greatly improved the catalytic CO oxidation performance due to their large specific surface area and excellent Co active sites.

Moss-like porous biochar loading Co3O4 nanoparticles as sulfur host maintain the stability of Li-sulfur batteries

Moss-like porous biochar loading Co3O4 nanoparticles as sulfur host maintain the stability of Li-sulfur batteries

Enhanced acetone sensing of MOFs derived Co3O4-ZIF hierarchical structure under the strategy of internal construction and external modification

Co3O4-ZIF-x (x = 0,1,2,3) composites have been prepared by in-situ growth of ZIF membrane on MOFs-derived hierarchical porous Co3O4 by the solvothermal method with adjusting the ratio of dimethylimidazole. The effects of ZIF membrane on Co3O4 structure and acetone-sensing properties are investigated by the techniques of XRD, Raman, SEM, TEM, BET, XPS and performance testing, and the possible gas-sensing enhancement mechanism is analyzed. The results show that the typical Co3O4-ZIF-1 sensor has the maximum response of 77.8–50 ppm acetone at 180 °C, the short response/recovery time of 7/35 s, and the low detection limit of 0.1 ppm (3.28). It also has the reliable acetone selectivity against to other interfering gases, as well as good repeatability and high stability. Its enhanced acetone-sensing property may be attributed to the synergistic effect of the improved surface state, high specific surface area, adjustable pore size and rich reaction activation sites, which caused by the hierarchical porous structure of MOFs-derived Co3O4 and the gas adsorption and enrichment effect of ZIF membrane, promoting the further reaction and diffusion of acetone. The “internal construction and external modification” role of MOFs playing in Co3O4 provides a new idea for designing high performance sensing materials.

Numerous active sites in self-supporting Co3O4 nanobelt array for boosted and stabilized 5-hydroxymethylfurfural electro-oxidation

Constructing an efficient electrocatalyst for the oxidation of 5-Hydroxymethylfurfural (HMF) to 2,5-furan dicarboxylic acid (FDCA) is highly desirable in achieving biomass conversion. Generally, there are two strategies to enhance the electrocatalyst’s activity: increasing the number of active site or increasing the intrinsic activity of each active site. Compared with the latter, the former is usually ignored in the HMF oxidation reaction (HMFOR), but it is very critical for practical applications. Herein, we fabricate a self-supporting three-dimensional porous Co3O4 nanobelt array decorated on nickel foam (P-Co3O4-NBA@NF) electrode with numerous active sites. Benefiting from the unique structural feature, P-Co3O4-NBA@NF electrode demonstrates nearly 100% of HMF conversion efficiency, 96.9% of FDCA selectivity, and 97.0% of Faraday efficiency. Notably, it can also deliver remarkable long-term stability over 30 continuous cycles. These exceptional features position P-Co3O4-NBA@NF as one of the promising electrocatalysts reported thus far for HMFOR.