Co3O4 Nanosheets Research Articles

Fe-doped porous Co3O4 nanosheets with highly efficient catalytic performance for soot oxidation

A series of CoxFe1-x-PNS materials were synthesized at room temperature through the one-pot MgO-mediated method and were then used as catalysts for soot oxidation. Of all the catalyst samples prepared, the porous Co0.8Fe0.2-PNS nanosheets exhibited the highest catalytic performance for soot oxidation under both loose and tight contact modes. The 2D nanosheets provided a larger external surface area for contact between the catalyst and soot, and the porous structure was beneficial to the adsorption and diffusion of reactant gas. It was found that Fe was successfully doped in the lattice of Co3O4, and the mechanism regarding how Fe doping enhances intrinsic activity was investigated by a series characterization and DFT calculations. The results indicated that Fe doping made it easier to form oxygen vacancies and adsorb gaseous O2, which effectively improved the catalytic activity of soot oxidation. Hence, it is believed that the synergy between the well-defined porous nanosheets morphology and the properties induced by the doping of Fe resulted in better catalytic activity. This study also provided insight into the design of 2D transition metal oxides nanosheets as catalysts for soot oxidation.

Cathode electrochemically reconstructed V-doped CoO nanosheets for enhanced alkaline hydrogen evolution reaction

• The crystalline V-doped CoO nanosheets were obtained by cathode electrochemical reconstruction of amorphous VCoO. • The crystallineV-doped CoO exhibited better HER active than amorphous VCoO. • Nanosheets structure could provide abundant active sites. • Vanadium doping effectively increased the intrinsic activity of CoO (1 1 1) and the number of active sites. • The V-doped CoO nanosheets display superb performance for HER at high potential. In the search for nonprecious metal catalysts to achieving active industrial hydrogen evolution reaction (HER), transition metal oxides (TMOs) have been proposed as promising candidates. In various synthetic methods for preparation of TMO electrocatalysts, electrochemical reconstruction, as one of the most efficient and controlled way, attracts much attentions. However, most of reported electrochemical reconstruction is usually carried out on the surface of anode via electrochemical oxidation reaction, and the investigations of cathode electrochemical reconstruction are rarely reported. Here, V-doped CoO nanosheets (V-CoO) are successfully prepared via cathode electrochemical reconstruction of amorphous VCoO. The reconstruction process and principle are studied in detail. Compared with the previous oxides, the obtained V-CoO possesses the promoted HER performance with overpotential of 280 mV at − 100 mA cm −2 and superior durability at − 1.07 V vs. RHE for 20 h. DFT calculations further reveals that vanadium doping effectively improves the intrinsic activity of oxides and HER active sites located at Co side of V-CoO (1 1 1) facet is the favorable H* adsorption site of reconstructed oxides. This work highlights the importance of electrochemical reconstruction on cathode to improve the HER activity of TMOs.

Lower coordination Co3O4 mesoporous hierarchical microspheres for comprehensive sensitization of triethylamine vapor sensor

Monitoring and detecting triethylamine (TEA) vapor are essential in the organic synthesis industry. Two-dimensional Co3O4 nanosheets with large surface areas and multiple active sites are ideal for fabricating chemiresistive gas sensors. However, the face-to-face stacking owing to the high surface energy of nanosheets, would cover up the active sites, obstruct gas diffusion, raise contact resistance, which all hinder its utilization for TEA detection. Herein, the Co3O4 mesoporous nanosheets were assembled into hierarchical microspheres by adding the structure-directing agent PVP K30 and combined with a proper annealing temperature, which optimized their grain size, specific surface area, pores structure, oxygen vacancies, and the atomic ratio of Co2+ to Co3+. And these ultimately improved the detection capability of TEA. The sensor based on Co3O4 sphere-300 exhibits the highest sensor response of 34.1–100 ppm TEA and a low detection limit (0.5 ppm) at a low working temperature of 150 °C. The promising properties are mainly due to the combination of several advantages that facilitate simultaneous chemical and electronic sensitization. This work prepared a high-performance TEA gas sensor and verified the improvement of comprehensive sensitization on the gas-sensing performance of two-dimensional metal oxide semiconductors.

Confined heterogeneous catalysis by boron nitride-Co3O4 nanosheet cluster for peroxymonosulfate oxidation toward ranitidine removal

Peroxymonosulfate (PMS) induced advanced oxidation processes hold great promise for heterogeneous oxidation reactions. In this study, boron nitride (BN)-Co3O4 nanosheet cluster (NC) was fabricated to facilitate PMS activation with a nanoconfined heterogeneous catalysis effect for the rapid removal of ranitidine (RAN) under mild conditions. The obtained BN-Co3O4 NC cluster exhibited efficient catalysis performance with a 99.5% removal efficiency for ranitidine in 5 min, and meanwhile this novel catalyst could be applied under a wide pH range (pH: 3–9) with still high degradation efficiencies. The porous structure of BN-Co3O4 NC provided a large number of channels for RAN and PMS molecules to enter the catalyst’s inner confinement space, resulting in a remarkable enhancement of catalytic performance. The kinetic rate constant for RAN degradation by the BN-Co3O4 NC/PMS system with 3–33 fold less catalyst dosage is much larger (1.58–213 fold) compared with the state-of-the-art. PMS activation by BN-Co3O4 NC was mainly due to the pathway of reduction via active radicals. Density functional theory calculations specified that the concomitant active radicals such as ∙OH and SO4∙− were mainly derived from PMS activation via O-O bond cleavage. This work provides a new perspective for regulating the structure of Co3O4 and elucidating the mechanism of PMS-induced heterogeneous catalytic oxidation.

Hypersensitized electrochemical detection of Hg(II) based on tunable sulfur-doped porous Co3O4 nanosheets: Promotion Co2+/Co3+ valence change cycle and adsorption via introducing S

Doping can effectively improve the performance of materials used for electrochemical detection, but non-metallic doping is rarely used in this regard, and the related electroanalytical mechanism is still not clear. Herein, a sulfur-doped porous Co3O4 nanosheets is prepared by hydrothermal synthesis. By controlling the amount of doped S, the Co3O4 with 10 mg S-doping (named as SC10) shows rich surface defects and high ratio of Co2+/Co3+, and demonstrates an excellent detection performance toward mercury ion (Hg(II)). Decent structural features of abundant surface defects and porous sheet structure provide more active sites and help the adsorption of Hg(II). Moreover, strong interaction of S and Hg improves the combining of SC10 and Hg(II) to obtain more Hg(II) on the electrode surface additionally. Meanwhile, the facilitated Co2+/Co3+ valence change cycle could also enhance the redox of Hg(II) to Hg(0) in the square wave anodic stripping voltammetry (SWASV) process. Consequently, the as-prepared SC10 modified electrode has an excellent sensitivity of 1027.46 μA μM−1 cm−2 and low LOD of 0.016 μM towards Hg(II). The SC10 shows excellent anti-interference and stability, as well as a satisfactory current response for actual water. This non-metal doped metal oxide is expected to become a promising electrode modification material.

Ultrathin polycrystalline Co3O4 nanosheets with enriched oxygen vacancies for efficient electrochemical oxygen evolution and 5-hydroxymethylfurfural oxidation

Surfactant-free, freestanding, and hierarchical two-dimensional (2D) polycrystalline cobalt oxide (Co3O4) nanosheets with enriched oxygen vacancies (Co3O4-VO) were synthesized by a topotactic conversion via rapid calcination of the solvothermally synthesized ultrathin cobalt oxide hydrate (CoOxHy) nanosheets. The topochemically transformed Co3O4-VO outperforms the as-synthesized P123-encapsulated CoOxHy nanosheets and their conventionally calcined Co3O4 counterpart for both electrochemical oxygen evolution and 5-hydroxymethylfurfural (HMF) oxidation to 2,5-furandicarboxylic acid (FDCA), owing to their largely preserved 2D structure and elimination of P123 for abundant exposed surface active sites. More importantly, the strain-induced oxygen vacancies at grain boundaries of Co3O4 nanocrystallines are also proposed to be responsible for the improved electrooxidation performance. Furthermore, Co3O4-VO exhibits remarkable long-term stability during the chronoamperometric test in 1 M KOH.

Surface Modification of Co3O4 Nanosheets to Promote Peroxymonosulfate Activation for Degradation of Atrazine

Surface Modification of Co3O4 Nanosheets to Promote Peroxymonosulfate Activation for Degradation of Atrazine

Co3O4-induced area-selective growth of Ni(OH)2 cellular arrays for high-capacity supercapacitor electrode

Three-dimensional (3D) hybrids are very valuable in the construction of supercapacitor electrodes. Ni(OH)2 cellular arrays were in-situ grown on nickel foam using Co3O4 nanosheets (NSs) as nucleating agent. The formation, microstructure and supercapacitance performance of the Co3O4/Ni(OH)2 cellular arrays are systematically investigated. The Co3O4/Ni(OH)2 arrays present an open cellular nanostructure with ultrathin Ni(OH)2 walls. The Co3O4/Ni(OH)2 prepared by hydrothermal reaction of 12 h delivers a super-high specific capacitance of 4396 F g−1 at 1 A g−1, above the theoretical capacitances of both the Ni(OH)2 and Co3O4. Additionally, the Co3O4/Ni(OH)2 electrode shows an excellent cycle performance by retaining 80.1% after 5000 cycles and a stable rate capability by decreasing 21.1% from 1 to 10 A g−1. The assembled asymmetric supercapacitor reaches a large energy density of 32 Wh kg−1 at 7999 W kg−1 by Co3O4/Ni(OH)2 as anode and reduced graphene oxides as cathode. The prominent high-capacity performance can be attributed to the cellular arrays, ultrathin hybrid NSs and synergetic reactions of the Ni(OH)2 and Co3O4. The proposed technology is also suitable for producing other multi-component oxide/hydroxide arrays as electroactive materials for energy storage devices.

Oxygen Plasma-Assisted Defect Engineering of Two-Dimensional Co3o4 Nanosheets for Wireless and High-Performance Monitoring of the Sensing Properties of Volatile Organic Compounds

Oxygen Plasma-Assisted Defect Engineering of Two-Dimensional Co3o4 Nanosheets for Wireless and High-Performance Monitoring of the Sensing Properties of Volatile Organic Compounds

Oxygen vacancies in Co3O4nanoarrays promote nitrate electroreduction for ammonia synthesis

Oxygen vacancy-enriched Co3O4nanosheet arrays enable ambient electrosynthesis of NH3vianitrate reduction, achieving a faradaic efficiency of 96.9% and a NH3yield of 12 157 μg h−1cm−2in 0.1 M NaOH with 0.1 M NO3−.

Boosting alkaline water splitting and the urea electrolysis kinetic process of a Co3O4 nanosheet by electronic structure modulation of F, P co-doping.

Designing non-precious metal electrocatalysts for accelerated electron transfer and richer active site exposure is necessary and challenging to achieve the versatility of electrocatalysts. In this research, a self-grown nanosheet array electrocatalyst on nickel foam with high structural stability is first rationally designed through suitable anionic doping. The combined experimental and theoretical calculations reveal that the F-P-Co3O4/NF material optimizes the adsorption energy of hydrogen/water through electron coupling, and its nanosheet structure provides abundant active sites, accelerating the mass and electron transfer in the reaction process. It is worth noting that the as-developed F-P-Co3O4/NF materials exhibit outstanding catalytic activity for overpotentials of 192 and 110 mV at a current density of 10 mA cm-2 for the oxygen evolution reaction and the hydrogen evolution reaction in 1 M KOH, respectively. More notably, an assembled F-P-Co3O4/NF//F-P-Co3O4/NF alkaline electrolytic cell requires only an ultra-low cell voltage of 1.53 V to achieve a current density of 10 mA cm-2, which is one of the best activities reported so far. Furthermore, F-P-Co3O4/NF also shows excellent performance for urea electrolysis. Theoretical calculations show that the superior activity of the F-P-Co3O4/NF catalyst is attributed to the optimal electron configuration and the lower Gibbs free energy of hydrogen adsorption due to co-doping of P and F. The work provides an alternative solution for the preparation of electrocatalysts with high structural stability, high catalytic activity and multifunction for alkaline water splitting and urea electrolysis.

In Situ Grown Co3o4 Nanosheets in the Interlayer Space of G-C3n4 for Efficient Removal of Hg0 from Flue Gas

In Situ Grown Co3o4 Nanosheets in the Interlayer Space of G-C3n4 for Efficient Removal of Hg0 from Flue Gas

Catalytic Oxidation of Formaldehyde on Ultrathin Co3o4 Nanosheets at Room Temperature: Effect of Enhanced Active Sites Exposure on Reaction Path

Catalytic Oxidation of Formaldehyde on Ultrathin Co3o4 Nanosheets at Room Temperature: Effect of Enhanced Active Sites Exposure on Reaction Path

In situ growth of CoO nanosheets on a carbon fiber derived from corn cellulose as an advanced hybrid anode for lithium-ion batteries

A facile method is proposed to prepare CoO/carbon fiber (CoO/CF) hybrids by employing corn cellulose as the biocarbon source for high-performance lithium ion batteries.

Honeycomb-like holey Co3O4 membrane triggered peroxymonosulfate activation for rapid degradation of organic contaminants

Heterogeneous advanced oxidation processes (AOPs) are commonly employed for the degradation of recalcitrant contaminants, however, practical application of heterogeneous AOPs has been limited by their low activation efficiency and inefficient utilization of radicals. Herein, this study demonstrates for the first time that 2D honeycomb-like holey membranes assembled by Co3O4 nanosheets, serve as an excellent activator for peroxymonosulfate (PMS) and aid in rapid pollutant removal. The Co3O4 membrane achieved 100% target pollutant ranitidine removal and a membrane retention time of only ~385 ms with the degradation rate 3–5 orders of magnitude faster than that achieved by conventional heterogeneous catalysis. Ranitidine degradation was maintained at >90% for 13 h of continuous-flow operation at a high flux of 176 L m−2 h−1 bar−1. Furthermore, the Co3O4 membrane could also effectively degrade several recalcitrant pollutants, including pharmaceutical personal care products, phenols, and dyes. SO4•– and •OH were identified as the primary reactive oxygen species in the Co3O4 membrane/PMS system, with Co providing the active site for PMS activation. This strategy of membrane-based AOP treatment offers helpful guidance for the design of other efficient heterogeneous catalytic systems and presents a novel approach to overcoming the limitations of conventional heterogeneous catalysis.

Ionic Liquid-Assisted Preparation of Co3O4 Nanosheets as a New and Efficient Catalyst for Green Synthesis of Various 1,5-Benothiazepine Derivatives in Water

Ionic Liquid-Assisted Preparation of Co3O4 Nanosheets as a New and Efficient Catalyst for Green Synthesis of Various 1,5-Benothiazepine Derivatives in Water

Porous Mn-doped Co3O4 nanosheets: Gas sensing performance and interfacial mechanism investigation with In situ DRIFTS

Unraveling the gas-solid interfacial sensing mechanism during gas sensing is very essential for the development of high-performance gas sensors. In this work, the Mn-doped Co3O4 porous nanosheets with 5.6 times higher response than pristine Co3O4 and short response/recovery time (55/30 s) for 100 ppm toluene gas is synthesized. More importantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is conducted to investigate the gas-solid interfacial sensing mechanism over 3-Mn-Co3O4. The interfacial reaction species have been monitored, such as methylbenzene, benzyl alcohol, benzaldehyde, benzoic acid, carbon monoxide, and water molecule. These species originate from the elementary and overall reactions during toluene gas sensing. The dynamic evolution of surface species could be divided into three stages of adsorption reaction, reaction balance, and desorption reaction. Furthermore, combined with the density function theory simulation calculation, the gas-solid interfacial sensing mechanism over 3-Mn-Co3O4 is proposed. Toluene molecule reacts with the surface active oxygen species resulting in the occurrence of a series of elementary reactions and the generation of intermediates. The products of overall reaction are CO2 and H2O during gas sensing. Our work implements a meaningful exploration of in situ DRIFTS in gas-sensing field and provides a distinctive view to understand the gas-soild interfacial gas-sensing mechanism.

Engineering Co2+/Co3+ redox activity of Ni-mediated porous Co3O4 nanosheets for superior Hg(II) electrochemical sensing: Insight into the effect of valence change cycle and oxygen vacancy on electroanalysis

Transition metal oxides (TMOs) have been recognized as promising sensing materials for heavy metal ions (HMIs) detection, mainly ascribing to a strong adsorption of HMIs on surface oxygen vacancies (OVs) of TMOs. However, the possibly more prominent role of valence change induced redox activity of TMOs in HMIs detection has not received its deserved attention, thus severely hindering the further development of TMOs-based HMIs detection. Herein, a facile strategy is proposed to co-engineer the redox activity and surface OVs of porous Co3O4 nanosheets by Ni doping. As a result, a boosted redox activity and an enhanced adsorption have been simultaneously achieved by optimizing the Ni doping level. Specifically, the 5% (atomic ratio) Ni-doped Co3O4 nanosheets exhibited best electroanalytical performance towards toxic Hg(II). More importantly, it has been demonstrated that the valence change cycle of Co cations (Co2+/Co3+) plays a more important role in electrochemical detection, rather than the adsorption of Hg(II) on OVs. Namely, the reduction of Hg(II) to Hg(0) on Co3O4 nanosheets can be effectively promoted by Ni-doping facilitated valence change cycle of Co cations (Co2+/Co3+). This work provides a feasible way to develop TMOs-based sensing materials by energetically synergizing their redox activity and adsorption ability towards HMIs simultaneously.

Electrolyte Dynamics Engineering for Flexible Fiber-Shaped Aqueous Zinc-Ion Battery with Ultralong Stability.

Flexible aqueous zinc-ion batteries (ZIBs) are considered as promising energy storage devices for wearable electronics due to their cost-effectiveness, environmental friendliness, and high theoretical energy density. Herein, a flexible fiber-shaped aqueous ZIB is demonstrated by using a self-assembled Co3O4 nanosheet array on a carbon nanotube fiber as the cathode and Zn nanosheets deposited on a carbon nanotube fiber as the anode. The cycle life span of the fiber-shaped battery is largely enhanced by a simple electrolyte dynamics engineering strategy of preadding a trace amount of Co2+ cations in the mild aqueous electrolyte. The assembled fiber-shaped ZIB shows a high specific capacity (158.70 mAh g-1 at 1 A g-1), superior rate capacity, and excellent cycling life span (97.27% capacity retention after 10,000 cycles). Additionally, the fiber-shaped ZIB also shows superior flexibility, which can charge a smart watch under deformed states. This work provides new opportunities for the development of flexible, safe, and high-performance energy storage devices for wearable electronics.

Inherent Facet-Dominant effect for cobalt oxide nanosheets to enhance photocatalytic CO2 reduction

Highly specific exposed to different crystal facets remarkably affect the CO2 reduction photoreactivity. Thereby, we give examples of well-interpretated Co3O4 nanosheets, which dominating with respective facets, {112} and {111}, to explore the reactivity of the photocatalysis's special exposed crystal facets in the photocatalytic CO2 reduction. The true photoreactivity of Co3O4-{112} were testified to be remarkably higher than Co3O4-{111} for both CO evolution and CH4 production reactions. Further photoelectrochemical detection studies have confirmed that the different reactivity is not only due to the different morphologies of the calcined materials under different temperature conditions, but controlled by the different exposing facets, giving rise to the photogenerated carriers and effective space separation. Under the calcination condition of 673 K, CO and CH4 evolution rates of Co3O4-{112} reached 96.4 and 18.94 μmol·g−1·h−1. The mechanism of the reaction was further confirmed by in-situ fourier transform infrared spectroscopy and DFT calculation. Effective separation of photogenerated carriers and specific flaky shapes, crystal facets, and surface atomic arrangement all contribute to the high activity of the carefully designed Co3O4 photocatalysis.