The synthesis of cobalt-carbon core-shell microspheres in supercritical carbon dioxide system was investi- gated. Cobalt-carbon core-shell microspheres with diameter of about 1μm were prepared at 350 ℃ for 12 h in a...The synthesis of cobalt-carbon core-shell microspheres in supercritical carbon dioxide system was investi- gated. Cobalt-carbon core-shell microspheres with diameter of about 1μm were prepared at 350 ℃ for 12 h in a closed vessel containing an appropriate amount of bis（cyclopentadienyl）cobalt powder and dry ice. Characterization by a variety of techniques, including X-ray powder diffraction, X-ray photoelectron spectroscopy, TransmissiOn electron microscope, Fourier transform infrared spectrum and Raman spectroscopy analysis reveals that each cobalt-carbon core-shell microsphere is made up of an amorphous cobalt core with diameter less than 1 μm and an amorphous carbon shell with thickness of about 200 nm. The possible growth mechanism of cobalt-carbon core-shell microspheres is discussed, based on the pyrolysis of bis（cyclopentadienyl）cobalt in supercritical carbon dioxide and the deposition of carbon or carbon clusters with odd electrons on the surface of magnetic cobalt cores due to magnetic attraction. Magnetic measurements show 141.41 emu/g of saturation magnetization of a typical sample, which is lower than the 168 emu/g of the corresponding metal cobalt bulk material. This is attributed to the considerable mass of the carbon shell and amorphous nature of the magnetic core. Control of magnetism in the cobalt-carbon core-shell microspheres was achieved by annealing treatments.展开更多
The electrochemical reduction of alkylaquabis (dimethylglyoximato)Cobalt(Ⅲ) in the absence and presence of β-Cyclodextrin (β-CD) was inveingated by means of cylic voltammetry. It was found that β-CD facilitates th...The electrochemical reduction of alkylaquabis (dimethylglyoximato)Cobalt(Ⅲ) in the absence and presence of β-Cyclodextrin (β-CD) was inveingated by means of cylic voltammetry. It was found that β-CD facilitates the cleavage of Co-C bond during the reduchon process.展开更多
利用可再生电力将二氧化碳转化为高附加值产品的电催化二氧化碳还原反应(CO_(2)RR)是一项具有革命性潜力的技术,因而备受关注.其中,一氧化碳被视为CO_(2)RR中最具经济效益的产物之一,可直接利用费托合成工艺将其用于合成醛、酮、烃类等...利用可再生电力将二氧化碳转化为高附加值产品的电催化二氧化碳还原反应(CO_(2)RR)是一项具有革命性潜力的技术,因而备受关注.其中,一氧化碳被视为CO_(2)RR中最具经济效益的产物之一,可直接利用费托合成工艺将其用于合成醛、酮、烃类等产品.酞菁钴(CoPc)作为单位点催化剂,因其高原子利用率和高催化选择性能,在二氧化碳转化为一氧化碳过程中具有很大优势.然而,CoPc无法为CO_(2)RR中的质子化过程提供足够质子,导致其在工业大电流密度下的效率较低.因此,探索一种能够解决CO_(2)RR中质子供给不足问题的高效电催化剂对于提升CO_(2)RR的性能至关重要.本文设计了具有增强质子供给作用的缺陷碳纳米管(d-CNT),将其作为导电载体分散CoPc,用于制备CoPc/d-CNT电催化剂.通过引入富缺陷的碳纳米管(d-CNT),加速水解离进而增加CO_(2)RR的质子供给量.X射线光电子能谱、X射线吸收近边光谱和扩展X射线吸收精细结构谱结果表明,CoPc/d-CNT成功合成,同时保留了CoPc完整的Co-N4配位结构.透射电镜、粉末X射线衍射谱和拉曼光谱共同表明,d-CNT表面缺陷相对于商用CNT明显增加.动力学实验和原位衰减全反射表面增强红外吸收光谱研究表明,含大量缺陷的d-CNT具有加速水解离的能力,显著提高了二氧化碳还原反应过程中的质子供给,从而促进了CoPc_上CO_(2)活化生成*COOH.同时,密度泛函理论计算结果表明,d-CNT表面缺陷位点上从吸附水(*H2O)到质子水(H3O+)的吉布斯自由能为0.74 eV,远低于CNT(超过2 eV),表明d-CNT促进了水解过程和质子传递,再次证实了d-CNT降低了水分子解离的势垒.通过实验和理论的共同验证,阐明了d-CNT中的缺陷能够促进水解离,改善CO_(2)RR反应过程中质子供给,增强CoPc高效催化CO_(2)RR的能力.因此,CoPc/d-CNT混合材料表现出较好的催化性能.在电流密度为500 mA cm^(-2)的流动电池中,CoPc/d-CNT的CO法拉第效率(FECO)高达96%.相对而言,CoPc/CNT在200 mA cm^(-2)时FECO已经下降到90%以下.此外,在150 mA cm^(-2)的电流密度下,CoPc/d-CNT能够在20 h内维持FECO超过90%.综上,本文通过引入具有水解离能力的缺陷碳位点,解决了单位点催化剂CoPc在CO_(2)RR中质子供给不足的问题,为设计高性能催化剂提供了新见解.展开更多
氟化钴具有良好的库伦效率、理论比容量、循环稳定性以及容量保持能力,表现出较好的电化学性能,在化学储能领域引起了研究人员的关注。以六水氯化钴为钴源、氟化铵为氟源,采用一步溶剂热法在活性碳布表面负载氟化钴晶体纳米片阵列,用TEM...氟化钴具有良好的库伦效率、理论比容量、循环稳定性以及容量保持能力,表现出较好的电化学性能,在化学储能领域引起了研究人员的关注。以六水氯化钴为钴源、氟化铵为氟源,采用一步溶剂热法在活性碳布表面负载氟化钴晶体纳米片阵列,用TEM、SEM和XRD考察了氟化钴的微观形貌结构和物相组成,利用电化学工作站得到了氟化钴的电化学循环稳定、比电容等性能。结果表明:该纳米片厚10~30 nm,垂直生长在碳布纤维表面呈交错网络状分布;在1 m A/cm^(2)的电流密度下,复合电极的比电容为826.6 F/g,循环充放电1000次后,比容量保持率为93.7%。本研究为氟化物基复合材料的短路径合成提供了一种可行方案,在碳布表面阵列式生长氟化物晶体,构筑全电化学活性的无粘结剂型复合电极,为优化氟化物的电化学性能提供了一种新的研究思路。展开更多
利用火焰法一步原位生成附着在泡沫镍上Co_(3)O_(4)修饰的碳纳米管(Co_(3)O_(4)/CNT/NF)。该方法仅需数十秒的反应时间,大大减少了制备时间。所得复合材料中泡沫镍骨架为导电基底,互相搭接、连接的碳纳米管无需黏接剂辅助附着于泡沫镍...利用火焰法一步原位生成附着在泡沫镍上Co_(3)O_(4)修饰的碳纳米管(Co_(3)O_(4)/CNT/NF)。该方法仅需数十秒的反应时间,大大减少了制备时间。所得复合材料中泡沫镍骨架为导电基底,互相搭接、连接的碳纳米管无需黏接剂辅助附着于泡沫镍骨架的表面,形成良好的导电通道和巨大的比表面积。活性纳米颗粒Co_(3)O_(4)均匀地分散在碳纳米管中。作为电催化电极,这种结构既保证良好的电子电导率,又暴露出催化剂材料大量的活性位点,促进其电催化性能的提升。结果显示,该电极材料双电层电容为34.1 mF cm^(-2),析氧反应(OER)中的过电位为288 mV@10 mA cm^(-2)和372 mV@100 mA cm^(-2),优于商用RuO_(2)催化剂。在全水解过程中,仅需要1.722 V的电位就可以达到10 mA cm^(-2)。展开更多
Through complexation reaction of arynyl Fe-S complexes A(μ-p-CH_3C_6H_4C≡CS)(μ- RS)Fe_2(CO)_6 with Co_2(CO)_6, eight mixed cluster complexes B[μ-p-CH_3C_6H_4C_2Co_2(CO)_6S](μ- RS)Fe_2(CO)_6 have been synthesized....Through complexation reaction of arynyl Fe-S complexes A(μ-p-CH_3C_6H_4C≡CS)(μ- RS)Fe_2(CO)_6 with Co_2(CO)_6, eight mixed cluster complexes B[μ-p-CH_3C_6H_4C_2Co_2(CO)_6S](μ- RS)Fe_2(CO)_6 have been synthesized. Reactivity of the complexation reaction is approximately equi- valent to that of the reaction of diarylacetylene with Co_2(CO)_8. Conformational analysis has shown that R groups in complexes A are linked to sulfur atoms by a-and e-bond, whereas that in B only by art e-type of bond.展开更多
基金ACKNOWLEDGMENT This work was supported Science Foundation of China by the National Natural （No.20273066）.
文摘The synthesis of cobalt-carbon core-shell microspheres in supercritical carbon dioxide system was investi- gated. Cobalt-carbon core-shell microspheres with diameter of about 1μm were prepared at 350 ℃ for 12 h in a closed vessel containing an appropriate amount of bis（cyclopentadienyl）cobalt powder and dry ice. Characterization by a variety of techniques, including X-ray powder diffraction, X-ray photoelectron spectroscopy, TransmissiOn electron microscope, Fourier transform infrared spectrum and Raman spectroscopy analysis reveals that each cobalt-carbon core-shell microsphere is made up of an amorphous cobalt core with diameter less than 1 μm and an amorphous carbon shell with thickness of about 200 nm. The possible growth mechanism of cobalt-carbon core-shell microspheres is discussed, based on the pyrolysis of bis（cyclopentadienyl）cobalt in supercritical carbon dioxide and the deposition of carbon or carbon clusters with odd electrons on the surface of magnetic cobalt cores due to magnetic attraction. Magnetic measurements show 141.41 emu/g of saturation magnetization of a typical sample, which is lower than the 168 emu/g of the corresponding metal cobalt bulk material. This is attributed to the considerable mass of the carbon shell and amorphous nature of the magnetic core. Control of magnetism in the cobalt-carbon core-shell microspheres was achieved by annealing treatments.
文摘The electrochemical reduction of alkylaquabis (dimethylglyoximato)Cobalt(Ⅲ) in the absence and presence of β-Cyclodextrin (β-CD) was inveingated by means of cylic voltammetry. It was found that β-CD facilitates the cleavage of Co-C bond during the reduchon process.
文摘利用可再生电力将二氧化碳转化为高附加值产品的电催化二氧化碳还原反应(CO_(2)RR)是一项具有革命性潜力的技术,因而备受关注.其中,一氧化碳被视为CO_(2)RR中最具经济效益的产物之一,可直接利用费托合成工艺将其用于合成醛、酮、烃类等产品.酞菁钴(CoPc)作为单位点催化剂,因其高原子利用率和高催化选择性能,在二氧化碳转化为一氧化碳过程中具有很大优势.然而,CoPc无法为CO_(2)RR中的质子化过程提供足够质子,导致其在工业大电流密度下的效率较低.因此,探索一种能够解决CO_(2)RR中质子供给不足问题的高效电催化剂对于提升CO_(2)RR的性能至关重要.本文设计了具有增强质子供给作用的缺陷碳纳米管(d-CNT),将其作为导电载体分散CoPc,用于制备CoPc/d-CNT电催化剂.通过引入富缺陷的碳纳米管(d-CNT),加速水解离进而增加CO_(2)RR的质子供给量.X射线光电子能谱、X射线吸收近边光谱和扩展X射线吸收精细结构谱结果表明,CoPc/d-CNT成功合成,同时保留了CoPc完整的Co-N4配位结构.透射电镜、粉末X射线衍射谱和拉曼光谱共同表明,d-CNT表面缺陷相对于商用CNT明显增加.动力学实验和原位衰减全反射表面增强红外吸收光谱研究表明,含大量缺陷的d-CNT具有加速水解离的能力,显著提高了二氧化碳还原反应过程中的质子供给,从而促进了CoPc_上CO_(2)活化生成*COOH.同时,密度泛函理论计算结果表明,d-CNT表面缺陷位点上从吸附水(*H2O)到质子水(H3O+)的吉布斯自由能为0.74 eV,远低于CNT(超过2 eV),表明d-CNT促进了水解过程和质子传递,再次证实了d-CNT降低了水分子解离的势垒.通过实验和理论的共同验证,阐明了d-CNT中的缺陷能够促进水解离,改善CO_(2)RR反应过程中质子供给,增强CoPc高效催化CO_(2)RR的能力.因此,CoPc/d-CNT混合材料表现出较好的催化性能.在电流密度为500 mA cm^(-2)的流动电池中,CoPc/d-CNT的CO法拉第效率(FECO)高达96%.相对而言,CoPc/CNT在200 mA cm^(-2)时FECO已经下降到90%以下.此外,在150 mA cm^(-2)的电流密度下,CoPc/d-CNT能够在20 h内维持FECO超过90%.综上,本文通过引入具有水解离能力的缺陷碳位点,解决了单位点催化剂CoPc在CO_(2)RR中质子供给不足的问题,为设计高性能催化剂提供了新见解.
基金Scientific and Technological Research Planning Project of the 13th Five Year Plan of Jilin Provincial Department of Education(JJKH20200237KJ,JJKH20210233KJ)the Fund of Jilin Institute of Chemical Technology(2020 No.22,2021 No.20,2021 No.48)Jilin Scientific and Technological Development Program,the Central Guide Local Scientific and Technological Development Fund,Jilin Province Natural Science Fund(YDZJ202201ZYTS405).
文摘氟化钴具有良好的库伦效率、理论比容量、循环稳定性以及容量保持能力,表现出较好的电化学性能,在化学储能领域引起了研究人员的关注。以六水氯化钴为钴源、氟化铵为氟源,采用一步溶剂热法在活性碳布表面负载氟化钴晶体纳米片阵列,用TEM、SEM和XRD考察了氟化钴的微观形貌结构和物相组成,利用电化学工作站得到了氟化钴的电化学循环稳定、比电容等性能。结果表明:该纳米片厚10~30 nm,垂直生长在碳布纤维表面呈交错网络状分布;在1 m A/cm^(2)的电流密度下,复合电极的比电容为826.6 F/g,循环充放电1000次后,比容量保持率为93.7%。本研究为氟化物基复合材料的短路径合成提供了一种可行方案,在碳布表面阵列式生长氟化物晶体,构筑全电化学活性的无粘结剂型复合电极,为优化氟化物的电化学性能提供了一种新的研究思路。
文摘利用火焰法一步原位生成附着在泡沫镍上Co_(3)O_(4)修饰的碳纳米管(Co_(3)O_(4)/CNT/NF)。该方法仅需数十秒的反应时间,大大减少了制备时间。所得复合材料中泡沫镍骨架为导电基底,互相搭接、连接的碳纳米管无需黏接剂辅助附着于泡沫镍骨架的表面,形成良好的导电通道和巨大的比表面积。活性纳米颗粒Co_(3)O_(4)均匀地分散在碳纳米管中。作为电催化电极,这种结构既保证良好的电子电导率,又暴露出催化剂材料大量的活性位点,促进其电催化性能的提升。结果显示,该电极材料双电层电容为34.1 mF cm^(-2),析氧反应(OER)中的过电位为288 mV@10 mA cm^(-2)和372 mV@100 mA cm^(-2),优于商用RuO_(2)催化剂。在全水解过程中,仅需要1.722 V的电位就可以达到10 mA cm^(-2)。
文摘Through complexation reaction of arynyl Fe-S complexes A(μ-p-CH_3C_6H_4C≡CS)(μ- RS)Fe_2(CO)_6 with Co_2(CO)_6, eight mixed cluster complexes B[μ-p-CH_3C_6H_4C_2Co_2(CO)_6S](μ- RS)Fe_2(CO)_6 have been synthesized. Reactivity of the complexation reaction is approximately equi- valent to that of the reaction of diarylacetylene with Co_2(CO)_8. Conformational analysis has shown that R groups in complexes A are linked to sulfur atoms by a-and e-bond, whereas that in B only by art e-type of bond.
