Co3O4 nanorods, nanobelts, nanosheets and cubic/octahedral nanoparticles have been successfully synthesized with tunable size from the nanoscale to the microscale, accompanied by a variation in the nature of the expos...Co3O4 nanorods, nanobelts, nanosheets and cubic/octahedral nanoparticles have been successfully synthesized with tunable size from the nanoscale to the microscale, accompanied by a variation in the nature of the exposed crystal planes. The products are formed by thermal treatment of Co（CO3）05（OH）-0.11H2O nanorod, nanobelt, nanosheet and nanocubic/nanooctahedral precursors at 250 ℃. Detailed characterization, including X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, and nitrogen adsorption and desorption isotherms, revealed that the as-prepared nanorods, nanobelts, and nanosheet Co3O4 samples are single crystalline and mesoporous in nature with a predominance of exposed high-energy （11-0） crystal planes. They exhibited excellent electrochemical properties in supercapacitors, showing higher capacitance and better rate capability than conventional cubic/octahedral COBO4 nanoparticles having exposed low-energy （100） and （111） planes. No decay in capacitance was observed when the scan rate was increased from 5 mV/s to 100 mV/s, or from I A/g to 10 A/g. The maximum value of the specific capacitance was calculated to be 162.8 F/g and the capacitance retention reached as high as 90%. Their excellent performance in supercapacitors is believed to result from the large-area exposure of active （110） crystal planes. The Co3O4 nanosheets showed the best performance due to their larger surface area and ability to provide a better pathway for charge transfer, and are promising electrode materials for application in practical supercapacitors.展开更多
In this work, we report enhanced electroactivity of Co304 nanocrystals （nanocubes, NCs and truncated nano-octahedra, TNO） on the exposed {111} facets as compared to the {001} facets in relation to the surface densit...In this work, we report enhanced electroactivity of Co304 nanocrystals （nanocubes, NCs and truncated nano-octahedra, TNO） on the exposed {111} facets as compared to the {001} facets in relation to the surface density and the activity of the octahedral Com species. Transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were em- ployed to characterize the crystal facets and materials properties. The enhanced electroactivity of {111 } crystal facets was evaluated by cyclic voltammetry and amperometric titration. Our results indicate that the {111 } facets in TNO has a better electroactivity for enzymeless glucose sensing with a decent glucose sensitivity of 32.54 μA （mmol/L）-1 cm-2.展开更多
Microsized single-crystalline Co3O4 has been synthesized by high-temperature hydrolysis of CoCD2H20 at 600℃. The samples were characterized by powder X-ray diffraction （XRD）, scanning electron microscopy （SEM） an...Microsized single-crystalline Co3O4 has been synthesized by high-temperature hydrolysis of CoCD2H20 at 600℃. The samples were characterized by powder X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results reveal that the as-prepared powders are microsized single-crystalline CO3O4 with cubic spinel structure. An increase in the high-temperature hydrolysis time results in the evolution of particle shapes from cube to quasi-sphere, and then to octahedron. The effect of NaCl additive on the surface morphologies of Co3O4 particles was experimentally investigated. The results indicate that the NaCl additive acts as an inert disperse phase in the high-temperature hydrolysis, and prevents the aggregation of Co3O4 particles effectively.展开更多
Hierarchical Co3O4 porous nanowires （NWs） have been synthesized using a hydrothermal method followed by calcination. When employed as a cathode catalyst in non-aqueous Li-oxygen batteries, the Co3O4 NWs effectively ...Hierarchical Co3O4 porous nanowires （NWs） have been synthesized using a hydrothermal method followed by calcination. When employed as a cathode catalyst in non-aqueous Li-oxygen batteries, the Co3O4 NWs effectively improve both the round-trip efficiency and cycling stability, which can be attributed to the high catalytic activities of Co3O4 NWs for the oxygen reduction reaction and the oxygen evolution reaction during discharge and charge processes, respectively.展开更多
An Ostwald ripening-based route is proposed to prepare Ni-rich layered cathodes with Co-rich surface for li- thium-ion batteries （LIBs）. Commercially available Nio.aCo0.1 Mn0.8（OH）2 and spray pyrolysis derived por...An Ostwald ripening-based route is proposed to prepare Ni-rich layered cathodes with Co-rich surface for li- thium-ion batteries （LIBs）. Commercially available Nio.aCo0.1 Mn0.8（OH）2 and spray pyrolysis derived porous Co304 are used as mixed precursors. During the lithiation reaction process under high-temperature, the porous Co304 microspheres scatter primary particles and spontaneously redeposit on the surface of Ni-rich spheres according to Ostwald ripening mechanism, forming the Ni-rich materials with Co-rich outer layers. When evaluated as cathode for LIBs, the resultant material shows ability to inhibit the cation disorder, relieves the phase transition from H2 to H3 and diminishes side re- actions between the electrolyte and Ni-rich cathode material. As a result, the obtained material with Co-rich outer layers exhibits much more improved cycle and rate performance than the material without Co-rich outer layers. Particularly, NCM-Co-1 （molar ratio of Nio.sCo0.1Mn0.1（OH）2/Co3Oa is 60：1） delivers a reversible capacity of 159.2 mA h g-1 with 90.5% capacity retention after 200 cycles at 1 C. This strategy pro- rides a general and efficient way to produce gradient sub- stances and to address the surface problems of Ni-rich cathode materials.展开更多
文摘Co3O4 nanorods, nanobelts, nanosheets and cubic/octahedral nanoparticles have been successfully synthesized with tunable size from the nanoscale to the microscale, accompanied by a variation in the nature of the exposed crystal planes. The products are formed by thermal treatment of Co（CO3）05（OH）-0.11H2O nanorod, nanobelt, nanosheet and nanocubic/nanooctahedral precursors at 250 ℃. Detailed characterization, including X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, and nitrogen adsorption and desorption isotherms, revealed that the as-prepared nanorods, nanobelts, and nanosheet Co3O4 samples are single crystalline and mesoporous in nature with a predominance of exposed high-energy （11-0） crystal planes. They exhibited excellent electrochemical properties in supercapacitors, showing higher capacitance and better rate capability than conventional cubic/octahedral COBO4 nanoparticles having exposed low-energy （100） and （111） planes. No decay in capacitance was observed when the scan rate was increased from 5 mV/s to 100 mV/s, or from I A/g to 10 A/g. The maximum value of the specific capacitance was calculated to be 162.8 F/g and the capacitance retention reached as high as 90%. Their excellent performance in supercapacitors is believed to result from the large-area exposure of active （110） crystal planes. The Co3O4 nanosheets showed the best performance due to their larger surface area and ability to provide a better pathway for charge transfer, and are promising electrode materials for application in practical supercapacitors.
基金financial support from the University of Queenslandthe support of the Centre for Microscopy and Microanalysis at the University of Queensland through their facilities,and the scientific and technical assistance
文摘In this work, we report enhanced electroactivity of Co304 nanocrystals （nanocubes, NCs and truncated nano-octahedra, TNO） on the exposed {111} facets as compared to the {001} facets in relation to the surface density and the activity of the octahedral Com species. Transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were em- ployed to characterize the crystal facets and materials properties. The enhanced electroactivity of {111 } crystal facets was evaluated by cyclic voltammetry and amperometric titration. Our results indicate that the {111 } facets in TNO has a better electroactivity for enzymeless glucose sensing with a decent glucose sensitivity of 32.54 μA （mmol/L）-1 cm-2.
基金Project(50704038) supported by the National Natural Science Foundation of ChinaProject(108170) supported by the Key Foundation of Ministry of Education,China
文摘Microsized single-crystalline Co3O4 has been synthesized by high-temperature hydrolysis of CoCD2H20 at 600℃. The samples were characterized by powder X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results reveal that the as-prepared powders are microsized single-crystalline CO3O4 with cubic spinel structure. An increase in the high-temperature hydrolysis time results in the evolution of particle shapes from cube to quasi-sphere, and then to octahedron. The effect of NaCl additive on the surface morphologies of Co3O4 particles was experimentally investigated. The results indicate that the NaCl additive acts as an inert disperse phase in the high-temperature hydrolysis, and prevents the aggregation of Co3O4 particles effectively.
文摘Hierarchical Co3O4 porous nanowires （NWs） have been synthesized using a hydrothermal method followed by calcination. When employed as a cathode catalyst in non-aqueous Li-oxygen batteries, the Co3O4 NWs effectively improve both the round-trip efficiency and cycling stability, which can be attributed to the high catalytic activities of Co3O4 NWs for the oxygen reduction reaction and the oxygen evolution reaction during discharge and charge processes, respectively.
基金the financial support of the National Basic Research Program of China (2014CB643406)the National Natural Science Foundation of China (51674296, 51574287, 51704332)+1 种基金the National Postdoctoral Program for Innovative Talents (BX201700290)the Fundamental Research Funds for the Central Universities of Central South University (2017zzts125)
文摘An Ostwald ripening-based route is proposed to prepare Ni-rich layered cathodes with Co-rich surface for li- thium-ion batteries （LIBs）. Commercially available Nio.aCo0.1 Mn0.8（OH）2 and spray pyrolysis derived porous Co304 are used as mixed precursors. During the lithiation reaction process under high-temperature, the porous Co304 microspheres scatter primary particles and spontaneously redeposit on the surface of Ni-rich spheres according to Ostwald ripening mechanism, forming the Ni-rich materials with Co-rich outer layers. When evaluated as cathode for LIBs, the resultant material shows ability to inhibit the cation disorder, relieves the phase transition from H2 to H3 and diminishes side re- actions between the electrolyte and Ni-rich cathode material. As a result, the obtained material with Co-rich outer layers exhibits much more improved cycle and rate performance than the material without Co-rich outer layers. Particularly, NCM-Co-1 （molar ratio of Nio.sCo0.1Mn0.1（OH）2/Co3Oa is 60：1） delivers a reversible capacity of 159.2 mA h g-1 with 90.5% capacity retention after 200 cycles at 1 C. This strategy pro- rides a general and efficient way to produce gradient sub- stances and to address the surface problems of Ni-rich cathode materials.
