ChemCatChem
·
2019
·Vol. 12
·期 3
·903-910
·
IF 4.495
Li Zhao,Song Shi,Meng Liu,Chen Chen,Guozhi Zhu,Jin Gao,Jie Xu
Graphical It's good for the microenvironment : Hexagonal mesoporous silicas with hydrophobic microenvironment modified by phenyl group was used to mimic the enzymes with Co 3 O 4 incorporated as active sites, the pore hydrophobic environment had an enhancement in the adsorption of ethylbenzene and in turn improved the catalytic selective oxidation activity than the hydrophilic one. Microenvironments in enzymes play crucial roles in controlling the activities of active centers. Here, hexagonal mesoporous silicas (HMS) with hydrophobic microenvironment was used to mimic the enzymes on the hydrocarbon oxidation with cobalt oxides incorporated as active sites. The variation of the structure and surface properties of the materials with phenyl group incorporation and the state of the supported cobalt oxides were carefully studied. It showed that cobalt oxides presented as Co 3 O 4 distributed evenly among the support, and the catalytic microenvironment was modified by the neighboring phenyl groups to be hydrophobic. This novel catalyst showed enhancement in the adsorption of ethylbenzene and in turn promoted the catalytic conversion than the hydrophilic one. 55.1 % conversion of ethylbenzene and 86.1 % selectivity for acetophenone could be obtained at 393 K for 6 h under 1.0 MPa of O 2 with free solvent. Hydrophobic microenvironment of pore surface was considered as an important factor for the better catalytic activity.
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INORGANIC CHEMISTRY
·
2019
·
IF 4.85
Dandan Wu,Runping Jia,Ming Wen,Shuai Zhong,Qingsheng Wu,Yongqing Fu,Shuhong Yu
A nanostructural catalyst with long-term durability under harsh conditions is very important for an outstanding catalytic performance. Herein, a new ultrastable PtCo/Co3O4–SiO2 nanocatalyst was explored to improve the catalytic performance of carbon monoxide (CO) oxidation by virtue of the surface active lattice oxygen derived from strong metal–support interactions. Such a structure can overcome the issues of Co3O4–SiO2 inactivation by water vapor and the Pt inferior activity at low temperature. Further, Co3O4–SiO2 nanosheets endow superior structure stability under high temperatures of up to 800 °C, which gives long-term catalytic cyclability of PtCo/Co3O4–SiO2 nanocomposites for CO oxidation. Moreover, the large specific surface areas (294 m2 g–1) of the nanosheet structure can expose abundant surface active lattice oxygen, which significantly enhanced the catalytic activity of CO oxidation at 50 °C over 30 days without apparent aggregation of PtCo nanoparticles after 20 cycles from 50 to 400 °C. It can be expected to be a promising candidate as an ultrastable efficient catalyst.
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Journal of Energy Chemistry
·
2019
·
IF 5.162
Han Wu,Min Wu,Boyang Wang,Xue Yong,Yushan Liu,Baojun Li,Baozhong Liu,Siyu Lu
Ammonia borane (AB) is an excellent candidate for the chemical storage of hydrogen. However, its practical utilization for hydrogen production is hindered by the need for expensive noble-metal-based catalysts. Herein, we report Co–Co 3 O 4 nanoparticles (NPs) facilely deposited on carbon dots (CDs) as a highly efficient, robust, and noble-metal-free catalyst for the hydrolysis of AB. The incorporation of the multi-interfaces between Co, Co 3 O 4 NPs, and CDs endows this hybrid material with excellent catalytic activity ( r B = 6816 m L H 2 min –1 g Co –1 ) exceeding that of previous non-noble-metal NP systems and even that of some noble-metal NP systems. A further mechanistic study suggests that these interfacial interactions can affect the electronic structures of interfacial atoms and provide abundant adsorption sites for AB and water molecules, resulting in a low energy barrier for the activation of reactive molecules and thus substantial improvement of the catalytic rate.
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ACS Applied Nano Materials
·
2018
·
IF 0
Mu Gao,Xiaofeng Lu,Sihui Chen,Di Tian,Yun Zhu,Ce Wang
Doping with transition metal ions has been regarded as one of the most effective means to optimize the catalytic efficiency of metal oxides. In this work, a general approach for the fabrication of Mo6+-doped Co3O4 (Mo–Co3O4) nanotubes for peroxidase mimicking has been demonstrated via an electrospinning method combined with a calcination process. The prepared Mo–Co3O4 nanotubes exhibited a higher peroxidase-like catalytic activity than pure Co3O4 nanotubes, and the highest catalytic activity is achieved when the molar fraction of Mo is 2.0%. The catalytic kinetic of Mo–Co3O4 nanotubes follows a typical Michaelis–Menten mechanism, representing a strong affinity to H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB) substrates. Because of the high catalytic efficiency of the Mo–Co3O4 nanotubes, we have developed a facile and efficient strategy for the sensitive colorimetric determination of l-cysteine with a low detection limit of 24.2 nM. This detection limit is superior to many previous reported enzyme-like detection systems. Furthermore, a favorable selectivity toward the determination of l-cysteine based on this approach is also achieved, showing bright prospects in environmental monitoring and biomedical analysis.
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JOURNAL OF ALLOYS AND COMPOUNDS
·
2018
·
IF 3.779
Yuanyuan Fu,Yanfei Li,Rihui Zhou,Yuzhe Zhang,Shouhui Chen,Yonghai Song,Li Wang
A new route to load Co 3 O 4 nanoparticles (NPs) on MOF-5 (MOF-5 was composed of 1,4-benzenedicarboxylate (BDC) and Zn 2+ via coordination bond (Zn 4 O(BDC) 3 ·(DMF) 8 (C 6 H 5 Cl)), where MOF indicates metal-organic framework) derived hierarchically porous carbon (MDPC) was proposed. Various techniques including scanning electron microscopy, transmission electron microscopy , Raman spectroscopy , powder X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and electrochemical methods were used to characterize the Co 3 O 4 NPs@MDPC. The results showed that the MDPC contained mesopores obtained by vaporizing ZnONPs and micropores came from MOF-5 self. Lots of nano-sized Co 3 O 4 NPs formed in MDPC's mesopores. The vast micropores of MDPC provided an effective channel for the transport of Li + when it was used as anode materials for lithium ion batteries (LIBs). The MDPC prevented Co 3 O 4 NPs from agglomerating effectively, which remained robust for superior rate capability during repeated lithiation/delithiation process. And the as-prepared Co 3 O 4 NPs@MDPC composites remained 94% reversible capacity from the second cycle. Furthermore, the as-prepared Co 3 O 4 NPs@MDPC anode manifested outstanding capability of 587.2 mA h g -1 at 2000 mA g −1 after 200 cycles, apparently superior to that of other Co 3 O 4 NPs@PC. The high capacity especially at high current density and exceptional rate capability of Co 3 O 4 NPs@MDPC manifested it is a promising anode material for LIBs.
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JOURNAL OF THE ELECTROCHEMICAL SOCIETY
·
2015
·Vol. 162
·期 6
·E68
·
IF 3.266
Xinhua Cheng,Diyong Tang,Dingding Tang,Hua Zhu,Dihua Wang
Electrochemical splitting of Co3O4 into cobalt powder and oxygen was realized by electrolysis in molten Na2CO3-K2CO3 at 1023 K using a solid oxide pellet cathode and a Ni11Fe10Cu alloy inert anode. The electro-reduction mechanism of Co3O4 was investigated in details by cyclic voltammetry measurements and potentiostatic electrolysis in a three-electrode cell combining with the composition and morphology characterization of the electrolytic products. The electro-reduction of Co3O4 in Na2CO3-K2CO3 melt mainly involves two steps by electrochemical formation of intermediate product of CoO and then the CoO is reduced to cobalt metal. NaxCoO2 intermediate was not detected by XRD measurements and EDX analysis, different from the electro-reduction of Fe2O3 in this melt. However, the particle size and morphology of the intermediate CoO is found to be dependent of the applied potential in the range of −0.35 V to −0.75 V vs. Ag/Ag2SO4 reference electrode. Metallic cobalt powder was prepared by potentiostatic electrolysis at potential more negative than −1.25 V (vs. Ag/Ag2SO4) or by constant cell voltage electrolysis under a cell voltage higher than 1.7 V using a Ni11Fe10Cu inert anode. A high current efficiency of 95.3% and a low electrolysis energy consumption of 2.16 kW·h/kg-Co represents a novel high efficiency and green process for Co extraction. The Co product is a mixture of FCC and HCP structure, which is affected by the applied cell voltage and deserves further investigation to recognize the structure controllable condition and mechanism.
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RSC Advances
·
2014
·Vol. 4
·期 58
·30573-30578
·
IF 3.708
Jun Wang,Bing Gao,Long Zhang,Rui Li,Jinpeng Shen,Zhiqiang Qiao,Guangcheng Yang,Fude Nie
Two-dimensional Co3O4 nanostructures with porous architectures are experiencing rapid development in functional material fields for their unique structures and properties. Porous Co3O4–C hybrid nanosheet (NS) arrays grown directly on various conducting substrates are synthesized by a controlled method for the first time via a facile hydrothermal synthesis approach in combination with heat treatment. These NS arrays reveal uniform hexagonal morphology and have combined properties of quasi-single-crystallinity and a pore network inside the architecture. A four-step formation mechanism is proposed to understand the growth process of nanosheet arrays grown on the substrate based on the change of morphology. Both the concentration of Co2+ and poly(vinylpyrrolidone) (PVP) play key roles in the formation of NS arrays. When tested as an anode material in lithium-ion batteries, the porous Co3O4–C hybrid NS arrays exhibit improved electrochemical properties of cyclic performance and high coulombic efficiency compared with the commercial Co3O4 and Co3O4/carbon nanocomposites. This approach, porous Co3O4–C NS arrays grown directly on different substrates (wafer, foam, alloy net, foil, especially flexible carbon cloth), provides an efficient route to produce NS arrays to meet the demand for diversity, and may be extended to synthesize other transition metal oxide materials for other applications.
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Nanoscale
·
2016
·Vol. 9
·期 2
·899-906
·
IF 7.76
Linxu Xu,Fang Cui,Jiajia Zhang,Yanjun Hao,Yan Wang,Tieyu Cui
Herein, an autocatalytic route to fabricate dual metal ion-equipped organic/inorganic hybrid silica, an ideal precursor for multifunctional silica-based composites integrated with well-dispersed Ag and Co3O4 nanoparticles was demonstrated. Significantly, by rational selection of reactants, such dual metal ion-equipped organic/inorganic hybrid silica can be synthesized through successive spontaneous reactions under near neutral conditions without an additional catalyst. Both the Ag+ and Co2+ ions are introduced into silica by chemical bonds, which favor the formation of small-sized and well-dispersed Ag and Co3O4 nanoparticles without aggregation in the entire silica matrix. After calcination, multifunctional silica composites equipped with well-dispersed Ag and Co3O4 nanoparticles were obtained. The as-obtained silica composites, as indicated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), have a spherical morphology and smooth surface. TEM tests also reveal the well dispersed fashion of Ag and Co3O4 nanoparticles. In addition, the obtained Ag–Co3O4@SiO2 composites exhibit good catalytic performance in the reduction of methylene blue (MB) with NaBH4 as a reducing agent, and can be readily recycled by an external magnetic field due to their superparamagnetic properties.
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JOURNAL OF ALLOYS AND COMPOUNDS
·
2017
·
IF 3.133
Wei Guo,Linlin Hou,Biao Hou,Yalin Guo
Pseudocapacitive materials, e.g. , MnO 2 and Co 3 O 4 , can significantly enhance the energy density of supercapacitors because of Faradaic reactions that can take place with these materials. Single-component electrodes have shown insufficient performance due to limited variations in electrode structures. Herein, we report a hierarchical electrode through growing networked Co 3 O 4 @MnO 2 hierarchical nanosheets (HNS) arrays directly on Ni foam. We adopt a one-step hydrothermal reaction followed by a simple staged post-annealing treatment which simplifies the synthesis procedure. When used as electrodes for supercapacitors, the Co 3 O 4 @MnO 2 HNS electrode shows good electrochemical performance, such as high areal/specific capacitances of 2.85 F cm −2 /2374 F g −1 at a current density of 1 mA cm −2 and long-term cycling stability of 4500 cycles. These encouraging results demonstrate this electrode design strategy is promising for developing high capacitance electrode materials for high energy density supercapacitors.
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Scientific Reports
·
2017
·Vol. 7
·期 1
·1-10
·
IF 4.259
Cui Guangliang,Zhang Pinhua,Chen Li,Wang Xiaoli,Li Jianfu,shi Changmin,Wang Dongchao
Gas sensors with high sensitivity at and below room temperature, especially below freezing temperature, have been expected for practical application. The lower working temperature of gas sensor is better for the manufacturability, security and environmental protection. Herein, we propose a H 2 S gas sensor with high sensitivity at and below room temperature, even as low as −30 °C, based on Cu 2 O/Co 3 O 4 nano/microstructure heteroarrays prepared by 2D electrodeposition technique. This heteroarray was designed to be a multi-barrier system, and which was confirmed by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and scanning probe microscopy. The sensor demonstrates excellent sensitivity, sub-ppm lever detection, fast response, and high activity at low temperature. The enhanced sensing property of sensor was also discussed with the Cu 2 O/Co 3 O 4 p-p heterojunction barrier modulation and Cu 2 S conductance channel. We realize the detection of the noxious H 2 S gas at ultra-low temperature in a more security and environmental protection way.
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Journal of Materials Chemistry A
·
2017
·Vol. 5
·期 11
·5342-5350
·
IF 8.867
Haoran Du,Chao Yuan,Kuangfu Huang,Wenhai Wang,Kai Zhang,Baoyou Geng
A mesoporous bowknot-like Co3O4 material has been synthesized through a facile hydrothermal method, using cobalt nitrate as the cobalt source, urea as the precipitator and gelatin as the guide agent, followed by calcination at 600 °C in air. Morphology characterization reveals that this bowknot-like Co3O4 material possesses a mesoporous structure consisting of nanoparticles. Electrochemical experiments illustrate that the mesoporous bowknot-like Co3O4 anode material exhibits a superior first and 100th reversible specific capacity of 1427.9 mA h g−1 and 1388.8 mA h g−1 at 0.2C, respectively. This material also delivers a high charge capacity of 751.3 mA h g−1 after 150 cycles at 2C. The novel preparation method and satisfactory performance make the bowknot-like Co3O4 a good candidate as a high-performance anode material for use in Lithium-Ion Batteries (LIBs).
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Nano Research
·
2017
·Vol. 10
·期 9
·3035-3048
·
IF 7.354
Liu Yanyan,Han Guosheng,Zhang Xiaoyu,Xing Congcong,Du Chenxia,Cao Huaqiang,Li Baojun
Controllable pyrolysis of metal−organic frameworks (MOFs) in confined spaces is a promising strategy for the design and development of advanced functional materials. In this study, Co-Co 3 O 4 @carbon composites were synthesized via pyrolysis of a Co-MOFs@glucose polymer (Co-MOFs@GP) followed by partial oxidation of Co nanoparticles (NPs). The pyrolysis of Co-MOFs@GP generated a core–shell structure composed of carbon shells and Co NPs. The controlled partial oxidation of Co NPs formed Co-Co 3 O 4 heterojunctions confined in carbon shells. Compared with Co-MOFs@GP and Co@carbon- n (Co@C- n ), Co-Co 3 O 4 @carbon- n (Co-Co 3 O 4 @C- n ) exhibited higher catalytic activity during NaBH 4 hydrolysis. Co-Co 3 O 4 @C-II provided a maximum specific H 2 generation rate of 5,360 mL·min −1 ·g Co
−1 at room temperature due to synergistic interactions between Co and Co 3 O 4 NPs. The Co NPs also endowed Co-Co 3 O 4 @C- n with the ferromagnetism needed to complete the magnetic momentum transfer process. This assembly-pyrolysis-oxidation strategy may be an efficient method of preparing novel nanocomposites.
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