Ultrafine Co3O4 Nanoparticles Research Articles

Interfacial engineering of RuO2 for electrocatalytic decomposition of Li2CO3 in Li–CO2/O2 battery

Li2CO3, the primary byproduct of Li–CO2/O2 batteries, is challenging to decompose electrochemically and its accumulation cause the short lifespan of the battery. Herein, we report strong interfacial interaction between the intimately interfaced ultrafine RuO2 and Co3O4 nanoparticles, which leads to transfer of electrons from Ru 4d orbital to Co 3d orbital via interfacial Ru–O–Co bridges. Such intense interaction is found to boost the adsorption of CO2 and O2 on the RuO2; more importantly, it can also effectively decrease the energy barrier for the rate determining step of decomposition of Li2CO3. Therefore, both the formation and decomposition kinetics of Li2CO3 during charge and discharge are efficiently enhanced on the Co3O4-interfaced RuO2 compared to the freestanding RuO2. Using such Co3O4-interfaced RuO2 as cathode catalyst, Li–CO2/O2 (V:V = 4:1) batteries depict an overpotential as low as 1.31 V and a cycling stability of 137 cycles under a constant capacity of 1000 mAh g−1, which is significantly better than that with only Co3O4 or RuO2; the enhanced decomposition kinetics of Li2CO3 is also confirmed by monitoring the release of CO2 using in-situ mass spectrum. This work emphasizes the role of interfacial oxygen bridges in enhancing electrocatalytic decomposition of Li2CO3.

Controllable preparation of ultrafine Co3O4 nanoparticles on H-ZSM-5 with superior catalytic performance in lean methane combustion

Co3O4/HZSM-5 has been proven a competitive catalyst in lean methane combustion. However, the poor dispersion of Co3O4 hinders its industrial application. To prevent the agglomerate of Co3O4 nanoparticles over zeolite, polyvinyl alcohol (PVA) assisted impregnation method is proposed to prepared Co3O4/H-ZSM-5 catalysts. It is found that the crosslink structure of PVA limits the free movement of Co2+ ions, by which Co3O4 nanoparticles are effectively dispersed on the surface of H-ZSM-5 and thus ultra-fine Co3O4 nanoparticles are obtained. The obtained catalysts exhibit stronger interaction between Co3O4 nanoparticles and H-ZSM-5 support, higher ratio of surface Co3+, which enhance the catalytic activity. Experiments show when the mass ratio of PVA to Co is 1.0, the temperature at methane conversion of 90 % (T90) is 391 °C, while T90 is 460 °C with the catalyst prepared by traditional impregnation method. Moreover, the catalyst shows a lower activation energy and much higher thermal stability.

Two-dimensional hollow carbon skeleton decorated with ultrafine Co3O4 nanoparticles for enhanced lithium storage

Transition metal oxides have shown high theoretical capacities as anode materials and have been considered as high potential materials to substitute graphite for composing new generations of lithium-ion batteries (LIBs). However, the considerable volume changes of transition metal oxide materials during practical processes have limited their applications. Herein, we report a simple approach to construct a two-dimensional (2D) hollow carbon skeleton decorated with ultrafine Co3O4 nanoparticles (Co3O4/C). This composite is derived from a leaf-like zeolitic imidazolate framework-L (ZIF-L (Co)) via etching coordination using tannic acid (TA). The Co3O4/C has a unique structure consisting of 2D carbon skeleton, ultrafine Co3O4 nanoparticle, and open channel, which can accelerate electron transport, alleviate volume change, and facilitate ion diffusion. Benefiting from these features, the LIBs assembled using Co3O4/C as anode material exhibits superior reversible cycle performance and impressive rate property. This study provides an efficient strategy for implementing transition metal oxide-based composites for energy storage applications.

Heterostructured ultrafine metal oxides nanoparticles anchored on Co-MOF nanosheets obtained by partial pyrolysis for promoted oxygen evolution reaction

The anchor of functional materials on metal-organic frameworks (MOFs) nanosheets to precisely construct fascinated heterostructures for electrocatalysis is highly promising but challenging owing to the different interfacial thermodynamics and nucleation kinetics. In this work, we design and synthesize ultrafine metal oxides nanoparticles (NPs) homogenously distributed on cobalt-based MOF (Co-MOF) nanosheets for oxygen evolution reaction (OER) by a facile solvothermal reaction and subsequent partially controlled pyrolysis. The ultrafine Co3O4 NPs with a particle size of about 1.5 nm can be obtained from the dispersed elemental Co in Co-MOF and uniformly generated on the surface of the MOF, which is crucial for the formation of the unique heterostructure. The well-designed Co-MOF-350 exhibits an efficient electrocatalytic activity with a low overpotential of 239 mV at a current density of 10 mA cm−2 and a small Tafel slope of 63 mV dec−1, and an outstanding catalytic stability for OER, much superior to the pure Co-MOF and Co3O4 electrocatalyst. The intriguing OER performance mainly originates from the desirable combination of the abundant active sites, the extended electron transport channel between ultrafine metal oxides and Co-MOF nanosheets. More importantly, the work will help to design novel heteroarchitectured MOFs-based composites as efficient and robust electrocatalysts for practical applications.

Quenching-induced surface modulation of perovskite oxides to boost catalytic oxidation activity

Quenching is a powerful method for modulating surface structures of metal oxide nanocatalysts to achieve high catalytic oxidation activities, but it is still challenging. Herein, a catalyst of ultrafine Co3O4 nanoparticles decorated on Co-doped LaMnO3 (Co3O4/LaCoxMn1−xO3) is synthesized via one-step quenching perovskite-type LaMnO3 nanocatalyst into an aqueous solution of cobalt nitrate, which exhibits significantly improved catalytic performance with toluene (1000 ppm) conversion of 90% at 269 °C under the gas hourly space velocity of 72000 mL g−1 h−1. The high catalytic activity correlates with large surface area, abundant oxygen vacancies and good reducibility. Furthermore, density functional theory calculations disclose that Co doping and interfacial effect of Co3O4/LaCoxMn1−xO3 can achieve lower C−H bond activation energy. These findings provide a unique and effective route towards surface modification of nanocatalysts.

A strategy for constructing highly efficient Co3O4-C@SiO2 nanofibers catalytic membrane for NH3-SCR of NO and dust filtration

The strategy of constructing catalytic membrane has a significant influence on its structure and performance. In this work, Co3O4-Cx@SiO2 nanofiber membranes (NFMs) were fabricated by an in-situ growth–pyrolysis–oxidation strategy. The Co3O4-Cx catalyst derived from ZIF-67 was wrapped around nanofibers, which helps to maintain a stable membrane structure, then suppressing the reduction of gas permeability. Among the Co3O4-Cx catalyst, the carbon skeleton can prevent the agglomeration of Co3O4 nanoparticles, obtaining an ultra-fine Co3O4 nanoparticles with high dispersibility, redox property and surface area. The obtained Co3O4-C300@SiO2 NFM exhibits outstanding ammonia selective catalytic reduction (NH3-SCR) denitrification activity (T90 = 225 °C at a GHSV of 77,000 h−1). The effect of catalyst loading on PM2.5 filtration performance of SiO2 NFM was also tested. Co3O4-C300@SiO2 NFM has higher filtration efficiency (99.99%) than SiO2 NFM at a lower pressure drop of 58 Pa, which suggests that catalyst loading via our method can improve the filtration performance of SiO2 NFM. This work might provide a universal strategy for the design and preparation of highly efficient catalytic membrane.

High lithium storage of Co3O4 enabled by integrating hollow and porous carbon scaffolds

The Co3O4, as a potential anode of lithium-ion batteries, has gained considerable attention because of high theoretical capacity. However, the Co3O4 is suffering from serious structure deterioration and rapid capacity fading due to its bulky volume change during cyclic charge/discharge process. Herein, to stabilize the lithium storage performance of the Co3O4 nanoparticles, a characteristic carbon scaffold (HPC) integrating hollow and porous structures has been fabricated by a well-designed method for the first time. The ultrafine Co3O4 nanoparticles are cleverly anchored on the HPC (HPC@Co3O4) and hence achieve significantly improved electrochemical properties including high capacity, improved reaction kinetics and outstanding cycle stability, showing high capacity of 1084.7 mAh g-1 after 200 cycles at 200 mA g-1 as well as 681.4 mAh g-1 after 300 cycles at 1000 mA g-1. The HPC@Co3O4 therefore shows good promising for application in advanced lithium-ion battery anodes. The results of the systematically material and electrochemical characterizations indicate that the synergistic effects of ultrafine Co3O4 nanoparticles and well-designed HPC scaffolds are responsible for the outstand performance of the HPC@Co3O4 anode. Moreover, this work can enrich the understanding and development of stable and high-performance metal oxide-based lithium-ion battery anodes for advanced lithium storage.

Confinement of ultrafine Co3O4 nanoparticles in nitrogen-doped graphene-supported macroscopic microspheres for ultrafast catalytic oxidation: Role of oxygen vacancy and ultrasmall size effect

• Confinement of ultrafine Co3O4 NPs in nitrogen-doped graphene-supported macroscopic microspheres were fabricated. • Ultrafine Co3O4 allowed a higher density of active sites to be exposed. • Oxygen vacancy and confined structure induced the interfacial mass/electron transfer. • Co3O4@N-rGO achieved ultra-fast SMX degradation. • Singlet oxygen dominated the degradation of SMX. Ultrasmall size and abundant defects are two key factors for enhancing the property of catalysts. However, how to simultaneously introduce defects and ultrasmall nanoparticles is still challenging. Herein, oxygen vacancies on confinement of ultrafine Co 3 O 4 NPs (6–14 nm) in nitrogen-doped graphene-supported macroscopic microspheres (Co 3 O 4 @N-rGO) were firstly fabricated and its large-scale applications in peroxymonosulfate activation for eliminating pollutants. Detailed characterizations manifested that ultrafine Co 3 O 4 allowed a higher density of active sites to be exposed, the synergy of abundant oxygen vacancies and confinement graphene-supported structure induced the interfacial mass/electron transfer. As expected, Co 3 O 4 @N-rGO achieved ultra-fast (0.453 min −1 ) sulfamethoxazole (SMX) degradation and 67.4 % mineralization within 10 min, which greatly outperformed that of Co 3 O 4 NPs from ZIF-67 (0.055 min −1 ). Integrated with ESR and quencher experiments, electrochemical analysis and XPS spectra before and after reaction, the degradation of SMX was dominated by singlet oxygen and other ROS had an auxiliary role. Moreover, a continuous fluidized-column reactor represented a cost-effective method for large-scale industrial wastewater treatment. This work not only verified the coaction of confined and ultrasmall NPs and oxygen vacancy but also provided a generally applicable strategy, thus expanding the applicability of heterogeneous catalysts.

Highly dispersed and ultrafine Co3O4@N-doped carbon catalyst derived from metal-organic framework for efficient oxygen reduction reaction

Electrocatalysts are composed of transition metal/metal oxide and N-doped carbon can overcome the sluggish kinetics of oxygen reduction reaction (ORR). Herein, The Co3O4/ketjen black (KB) @MOF-derived with uniformly dispersed and ultrafine Co3O4 nanoparticles (1-5 nm) is synthesized by a facile in-suit method and subsequent mild pyrolysis process. It exhibits enhanced activity with onset potential (Eonset) of 0.96 V (vs. RHE) and a half-wave potential (E1/2) of 0.86 V (vs. RHE) in 0.1 M KOH solution, the excellent durability with E1/2 a small negative shift of 10 mV after 5000 continuous cycles and good methanol-tolerance property. The ultrahigh catalytic performance of Co3O4/KB@MOF-derived can be ascribed to the small particle size range of 1-5 nm of Co3O4, as well as the strong interaction between the in-situ formed N-Co3O4 active sites and substrate under the mild calcination temperature. Above all, these indicate that the as-prepared Co3O4/KB @MOF-derived may be a good alternative to commercial Pt-based catalysts.

Core–shell Co3O4@FeOx catalysts for efficient oxygen evolution reaction

Rational fabrication of oxygen evolution reaction (OER) electrocatalysts based on earth-abundant elements is crucial for sustainable energy applications. Although Fe–Co-based (oxy)hydroxides show excellent catalytic activity for OER, a comprehensive understanding of the role of Fe and Co is still lacking. Here, we prepared a core–shell Co3O4@FeOx catalyst with an ultrathin FeOx (<1 nm) coating onto ultrafine Co3O4 nanoparticles (~3.1 nm), which exhibit higher OER activity than Fe/Co-based mixed oxides. The enhanced OER electrocatalytic performance is attributed to the introduction of ultrathin FeOx, which can (1) combine water molecules to promote the reaction, (2) enhance the charge transfer ability of Co3O4, and (3) speed up the diffusion of the reactant water close to the active sites and the produced oxygen away from the active sites.

Novel and highly efficient catalyst for Li–O2 battery: Porous LaCo0.6Ni0.4O3 nanofibers decorated with ultrafine Co3O4 nanoparticles

It is crucial to design effective cathode catalysts for high performance of Li–O2 batteries (LOBs). Herein, porous LaCo0.6Ni0.4O3 nanofibers decorated with ultrafine Co3O4 nanoparticles (Co3O4@LCN NFs) are designed and employed as cathode catalyst for LOBs. The X-ray photoelectron spectroscopy measurement results suggested that uniform dispreading of Co3O4 nanoparticles on LCN NFs surface could largely increase the surface chemisorbed oxygen, resulting in enhanced catalytic activity. Furthermore, with the assistance of Co3O4 nanoparticles, Co3O4@LCN NFs can significantly facilitate O2 adsorption and diffusion, Li2O2 nucleation/decomposition and the formation of tiny sheet-like Li2O2, thereby achieving a low charge overpotential. A high specific capacity of 11,288 mA h g−1, a low charge voltage plateau of 3.72 V at first cycle and excellent cycle stability of 116 cycles at 1000 mA g−1 are obtained for LOBs with Co3O4@LCN NFs.

Ultrafine Co3 O4 Nanoparticles within Nitrogen-Doped Carbon Matrix Derived from Metal-Organic Complex for Boosting Lithium Storage and Oxygen Evolution Reaction.

Transition metal oxides have recently received great attention for application in advanced lithium-ion batteries (LIBs) and oxygen evolution reaction (OER). Herein, the ethylenediaminetetraacetic cobalt complex as a precursor to synthesize ultrafine Co3 O4 nanoparticles encapsulated into a nitrogen-doped carbon matrix (NC) composites is presented. The as-prepared Co3 O4 /NC-350 obtained by pyrolysis at 350 °C demonstrates superior rate performance (372 mAh g-1 at 5.0 A g-1 ) and high cycling stability (92% capacity retention after 300 cycles at 1.0 A g-1 ) as anode for LIBs. When evaluated as an electrocatalyst for OER, the Co3 O4 /NC-350 achieves an overpotential of 298 mV at a current density of 10 mA cm-2 . The NC-encapsualted porous hierarchical structure assures fast and continuous electron transportation, high activity sites, and strong structural integrity. This works offers novel complex precursors for synthesizing transition metal-based electrodes for boosting electrochemical energy conversion and storage.

Synthesis of ultrafine Co3O4 nanoparticles encapsulated in nitrogen-doped porous carbon matrix as anodes for stable and long-life lithium ion battery

Hybrid nanostructures with ultrafine metal oxides in porous nitrogen-doped carbon matrix have received great attention for the enhancing performance of lithium-ion batteries because of their advantages in effectively solving the problems during the discharge/charge processes, such as low conductivity, large volume expansion, and long diffusion path for the fast transfer of Li+ ion. Herein, we report a facile strategy for the synthesis of ultrafine Co3O4 nanoparticles uniformly encapsulated into nitrogen-doped porous carbon matrix (Co3O4@NC) through pyrolysis of metal-organic frameworks (MOFs) followed by a hydrothermal oxidation method. Moreover, Co3O4@NC inherited the advantage of MOFs with porous structure, and the as-synthesized Co3O4 nanoparticles uniformly distributed into the simultaneously generated nitrogen-doped carbon matrix. Benefiting from its unique structural features, Co3O4@NC exhibits a large discharge capacity of 1017 mAh g−1 after 100 cycles at 100 mA g−1, and the long reversible capacity of 731 mAh g−1 can be retained after 1000 cycles at 1000 mA g−1, indicating that Co3O4@NC has potential application in lithium-ion batteries with long cycling life and high power density.

Metal-organic framework-derived hollow Co3O4/carbon as efficient catalyst for peroxymonosulfate activation

Concurrently rational optimization and design of the structure and composition of catalysts are significant for improving its catalytic performance. In this report, a novel hollow carbon supported ultrafine Co3O4 nanoparticles (HCo3O4/C) with a diameter of 6–12 nm were prepared as an active catalyst for peroxymonosulfate (PMS) activation. Initially, the zeolitic-imidazole-framework (ZIF-67) was synthesized followed by top-down etching strategy to get the hollow structure. Finally, as prepared hollow ZIF-67 was used as a precursor to fabricate HCo3O4/C. To understand the effects of structure and final composition on catalytic performance, another material, solid carbon supported Co3O4 nanoparticles (SCo3O4/C) was synthesized for comparison. The catalytic efficiency in control experiments between HCo3O4/C and SCo3O4/C was identified; in which HCo3O4/C demonstrated more than two times improved catalytic efficiency as compared to a solid structure. Interestingly, the HCo3O4/C catalyst exhibits better efficiency for PMS activation to generate sulfate radicals (SO4−) and the results show that degradation rate of targeted pollutant bisphenol A (BPA) was achieved up to 97% in 4 min, which is higher than other reported catalysts. The other factors which could influence PMS activation were also analyzed as well, for instance, the solution pH, catalyst loading, pollutant (BPA) concentration, system temperature and effect of organic molecules. Moreover, the Liquid chromatography-mass spectrometry (LC–MS) was used to identify the BPA degraded intermediate products. This work provides a new prospect into the synthesis of high-performance metal-organic framework (MOF) derived catalysts with exceptional properties, which may encourage the employ of hollow MOF materials in more practical applications.

Rambutan‐Like Hybrid Hollow Spheres of Carbon Confined Co3O4 Nanoparticles as Advanced Anode Materials for Sodium‐Ion Batteries

AbstractTransition metal oxides, possessing high theoretical specific capacities, are promising anode materials for sodium‐ion batteries. However, the sluggish sodiation/desodiation kinetics and poor structural stability restrict their electrochemical performance. To achieve high and fast Na storage capability, in this work, rambutan‐like hybrid hollow spheres of carbon confined Co3O4 nanoparticles are synthesized by a facile one‐pot hydrothermal treatment with postannealing. The hierarchy hollow structure with ultrafine Co3O4 nanoparticles embedded in the continuous carbon matrix enables greatly enhanced structural stability and fast electrode kinetics. When tested in sodium‐ion batteries, the hollow structured composite electrode exhibits an outstandingly high reversible specific capacity of 712 mAh g−1 at a current density of 0.1 A g−1, and retains a capacity of 223 mAh g−1 even at a large current density of 5 A g−1. Besides the superior Na storage capability, good cycle performance is demonstrated for the composite electrode with 74.5% capacity retention after 500 cycles, suggesting promising application in advanced sodium‐ion batteries.

Graphite-graphene architecture stabilizing ultrafine Co3O4 nanoparticles for superior oxygen evolution

Tremendous strides have been made in active and stable electrocatalysts of oxygen evolution reaction (OER) for water splitting to produce hydrogen. Nevertheless, the electrocatalysts with highly exposed active sites, fast electron/charge and mass transfer capabilities and long-term stability are still requisite. An efficient strategy of electrochemical activation is presented to fabricate the graphite-graphene Janus architecture and further stabilize the ultrafine Co3O4 nanoparticles for OER. The wrinkled and cross-linked graphene sheets that are in-situ formed and firmly bonded on the conductive graphite foil, act as pillared spacer for fast mass transport and anchoring sites for nucleation and growth of uniform distributed Co3O4 active species. The interlayer graphite contributes to the fast charge transfer as conductive substrate/framework. Benefitting from these merits, the resultant electrocatalyst achieves the outstanding OER performance with small overpotential (301 mV at 10 mA cm−2), low Tafel slope (47 mV dec−1) and long-term durability in basic medium.

Synthesis of an ultra-fine Co3O4 / graphene composite by one-step hydrothermal process and its effective catalytic performance on thermal decomposition of ammonium perchlorate

ABSTRACTThe Co3O4/graphene composite was prepared by a facile one-step method under hydrothermal conditions. During this hydrothermal synthesis process, graphene oxide was reduced to graphene with three-dimensional networks structure and ultra-fine Co3O4 nanoparticles were simultaneously deposited on graphene sheets. The average particle size of the ultra-fine near-spherical Co3O4 nanoparticles on the surface of graphene was in the range of 10–20 nm. The influence of as-prepared composite on the thermal decomposition of ammonium perchlorate show a strong catalytic effect. The decomposition temperature was decreased by 95.2° when adding 3% Co3O4/graphene composite and the low temperature decomposition meanwhile disappeared.

Space-Confined Earth-Abundant Bifunctional Electrocatalyst for High-Efficiency Water Splitting.

Hydrogen generation from water splitting could be an alternative way to meet increasing energy demands while also balancing the impact of energy being supplied by fossil-based fuels. The efficacy of water splitting strongly depends on the performance of electrocatalysts. Herein, we report a unique space-confined earth-abundant electrocatalyst having the bifunctionality of simultaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), leading to high-efficiency water splitting. Outperforming Pt/C or RuO2 catalysts, this mesoscopic, space-confined, bifunctional configuration is constructed from a monolithic zeolitic imidazolate framework@layered double hydroxide (ZIF@LDH) precursor on Ni foam. Such a confinement leads to a high dispersion of ultrafine Co3O4 nanoparticles within the N-doped carbon matrix by temperature-dependent calcination of the ZIF@LDH. We demonstrate that the OER has an overpotential of 318 mV at a current density of 10 mA cm-2, while that of HER is -106 mV @ -10 mA cm-2. The voltage applied to a two-electrode cell for overall water splitting is 1.59 V to achieve a stable current density of 10 mA cm-2 while using the monolithic catalyst as both the anode and the cathode. It is anticipated that our space-confined method, which focuses on earth-abundant elements with structural integrity, may provide a novel and economically sound strategy for practical energy conversion applications.

High-performance lithium storage based on the synergy of atomic-thickness nanosheets of TiO2(B) and ultrafine Co3O4 nanoparticles

Lithium ion batteries (LIBs) are critical constituents of modern day vehicular and telecommunication technologies. Transition metal oxides and their composites have been extensively studied as potential electrode materials for LIBs. However, inefficient lithiation, poor electrical conductivity, and drastic volume change during cycling result in low reversible capacity and rapid capacity fading, and thus hinder the practical applications of those electrodes. In this work, we report a facile synthesis of a novel hierarchical composites, which consist of ultrafine Co3O4 nanoparticles uniformly dispersed on TiO2(B) nanosheets with atomic thickness (Co3O4 NPs@TiO2(B) NSs). When tested as anode material for LIBs, the Co3O4 NPs@TiO2(B) NSs sample with optimized composition shows a reversible capacity of ∼677.3 mAhg−1 after 80 cycles at a current density of 100 mAg−1. A capacity of 386.2 mAhg−1 is still achieved at 1000 mAg−1. The synergistic effect of ultrafine Co3O4 nanoparticles and atomic-thickness TiO2(B) nanosheets is responsible for the enhanced electrochemical performance.

Facile synthesis of ultrafine cobalt oxide nanoparticles for high-performance supercapacitors

The ultrafine Co3O4 nanoparticles are successfully prepared by a novel solvothermal–precipitation approach which exploits the supernatant liquid of Co3O4 nanoflake micropheres synthesized by solvothermal method before. Interestingly, the water is only employed to obtain the ultrafine nanoparticles in supernatant liquid which was usually thrown away before. The microstructure measurement results of the as-grown samples present the homogeneous disperse ultrafine Co3O4 nanoparticles with the size of around 5–10nm. The corresponding synthesis mechanism of the ultrafine Co3O4 nanoparticles is proposed. More importantly, these ultrafine Co3O4 nanoparticles obtained at 250°C show the highest specific capacitance of 523.0Fg−1 at 0.5Ag−1, 2.6 times that of Co3O4 nanoflake micropheres due to the quantum size effect. Meanwhile, the sample annealed under 350°C possesses the best cycling stability with capacitance retention of 104.9% after 1500 cycles. These results unambiguously demonstrate that this work not only provides a novel, facile, and eco-friendly approach to prepare high-performance Co3O4 nanoparticles electrode materials for supercapacitors but also develops a widely used method for the preparation of other materials on a large scale.