Transition metal carbide （TMC） nanomaterials are promising alternatives to Pt, and are widely used as heterogeneous electrocatalysts for the electrochemical hydrogen evolution reaction （HER）. In this work, a bromi...Transition metal carbide （TMC） nanomaterials are promising alternatives to Pt, and are widely used as heterogeneous electrocatalysts for the electrochemical hydrogen evolution reaction （HER）. In this work, a bromide-induced wet-chemistry strategy to synthesize Co2C nanoparticles （NPs） was developed. Such NPs exhibited high electrocatalytic activity （η= 181 mV for j = -10 mA·cm^-2） and long-term stability （no obvious performance decrease after 4,000 cycles） for the HER. This study will pave the way for the design and fabrication of TMC NPs via a wet- chemistry method, and will have significant impacts on broader areas such as nanocatalysis and energy conversion.展开更多
以对苯二甲酸(H_2BDC)为配体、乙酸钴为Co源、水作溶剂,通过共沉淀法合成了金属有机框架材料(Co-BDC M OFs);以其为前驱体分别在乙炔和氩气氛下采用化学气相沉积法制备了核壳结构Co@C催化剂。结合XRD、氮吸附、SEM、TEM、XPS、TGA和Rama...以对苯二甲酸(H_2BDC)为配体、乙酸钴为Co源、水作溶剂,通过共沉淀法合成了金属有机框架材料(Co-BDC M OFs);以其为前驱体分别在乙炔和氩气氛下采用化学气相沉积法制备了核壳结构Co@C催化剂。结合XRD、氮吸附、SEM、TEM、XPS、TGA和Raman光谱等手段对Co@C催化剂的结构和组成进行了表征,考察了该催化剂在费托合成反应中的活性及稳定性。结果表明,炭化气氛对炭层结构的石墨化程度有较大影响,而对金属Co核的物相结构和粒径影响较小;乙炔气氛有助于形成多孔的石墨炭壳,从而促进烃链的生长,Co@C-C_2H_2催化剂上的C_(5+)烃产物选择性高达82. 66%,反应过程中催化剂物相由单相金属Co转变为金属Co与Co_2C的混合相,且无失活现象发生,表明Co_2C具有较高的费托反应催化活性。展开更多
碳化钴(Co2C)在费托合成制低碳烯烃(Fischer-Tropsch to Olefin, FTO)中起着重要的催化作用。通过X射线衍射(X-ray Diffraction, XRD)、X射线吸收精细结构(X-ray Absorption Fine Structure, XAFS)等表征与方法,对碱金属在CoMn催化FTO...碳化钴(Co2C)在费托合成制低碳烯烃(Fischer-Tropsch to Olefin, FTO)中起着重要的催化作用。通过X射线衍射(X-ray Diffraction, XRD)、X射线吸收精细结构(X-ray Absorption Fine Structure, XAFS)等表征与方法,对碱金属在CoMn催化FTO中形成碳化钴的影响进行了研究。在钠(Na)、钾(K)元素的影响下,CoMn催化剂在活性评测中,低碳非饱和烃与低碳饱和烃的比例高达17.4与9.4,且仅有较低的甲烷(CH4)产生,而锂(Li)对CoMn催化剂的选择性影响较弱。通过XRD表征,发现Na、K对CoMn催化剂形成Co2C有很好的促进效果。XAFS揭示了CoMn催化剂的电子结构,催化反应后形成碳化钴的配位结构,为研究CoMn催化剂微观结构提供了基础理论。展开更多
Three calculational models, statistical associating fluid theory (SAFT), modified SAFT, and Boublík Alder Chen Kreglewshi (BACK) are compared for supercritical CO 2 C 2H 5OH using a set of van der Waals ...Three calculational models, statistical associating fluid theory (SAFT), modified SAFT, and Boublík Alder Chen Kreglewshi (BACK) are compared for supercritical CO 2 C 2H 5OH using a set of van der Waals type mixing rules for both the BACK equation of state (EOS) and the SAFT EOS. Equations are presented for the residual Helmholtz free energy, residual chemical potentials, and compressibilty factor for mixtures. A comparison with experimental vapor liquid equilibrium (VLE) data reveals that the BACK EOS together with the suggested mixing rules provides more accurate prediction of the binary system than the SAFT or the modified SAFT model with no adjustable binary parameters. The correlation results are improved with an adjustable parameter. 展开更多
Biochar application to cropland has been recommended as a strategy to reduce increasing at-mospheric CO2 concentrations and mitigate climate change.However,the direction and magnitude of responses of greenhouse gas(GH...Biochar application to cropland has been recommended as a strategy to reduce increasing at-mospheric CO2 concentrations and mitigate climate change.However,the direction and magnitude of responses of greenhouse gas(GHG)fluxes to biochar application to cropland remain unclear.Our meta-analysis of 296 observations across 61 studies for the first time quantitatively estimated the effects of biochar amendment on fluxes of three GHGsCO2,N2O,and CH4.The results showed that biochar application led to a significant change in soil GHGs emissions:in general,19%for CO2,−16%for N2O(P<0.05),but no pronounced change in CH4 emissions;in paddy,−5%for CO2,−20%for N2O,but+19%for CH4(P<0.05);in upland,−18%for N2O,+12%for CO2,and high uncertainty for CH4.The responses of soil GHG flux-es to biochar application were regulated mainly by experiment length,biochar application rate,biochar properties,providing a new perspective for more comprehensive understanding on biochar.The bio-char derived from husk was recommended to apply to cropland with an application rate of 20-30 t·ha^(−1).展开更多
基金Acknowledgements This work was financially supported by the National Natural Science Foundation of China （Nos. 21473003 and 21303119） and the National Basic Research Program of China （No. 2013CB933100）. C. Y. acknowledges the financial support of China Postdoctoral Science Foundation （No. 2015M580011）. XAS analysis was performed at the Beijing Synchrotron Radiation Fadlity.
文摘Transition metal carbide （TMC） nanomaterials are promising alternatives to Pt, and are widely used as heterogeneous electrocatalysts for the electrochemical hydrogen evolution reaction （HER）. In this work, a bromide-induced wet-chemistry strategy to synthesize Co2C nanoparticles （NPs） was developed. Such NPs exhibited high electrocatalytic activity （η= 181 mV for j = -10 mA·cm^-2） and long-term stability （no obvious performance decrease after 4,000 cycles） for the HER. This study will pave the way for the design and fabrication of TMC NPs via a wet- chemistry method, and will have significant impacts on broader areas such as nanocatalysis and energy conversion.
文摘以对苯二甲酸(H_2BDC)为配体、乙酸钴为Co源、水作溶剂,通过共沉淀法合成了金属有机框架材料(Co-BDC M OFs);以其为前驱体分别在乙炔和氩气氛下采用化学气相沉积法制备了核壳结构Co@C催化剂。结合XRD、氮吸附、SEM、TEM、XPS、TGA和Raman光谱等手段对Co@C催化剂的结构和组成进行了表征,考察了该催化剂在费托合成反应中的活性及稳定性。结果表明,炭化气氛对炭层结构的石墨化程度有较大影响,而对金属Co核的物相结构和粒径影响较小;乙炔气氛有助于形成多孔的石墨炭壳,从而促进烃链的生长,Co@C-C_2H_2催化剂上的C_(5+)烃产物选择性高达82. 66%,反应过程中催化剂物相由单相金属Co转变为金属Co与Co_2C的混合相,且无失活现象发生,表明Co_2C具有较高的费托反应催化活性。
文摘碳化钴(Co2C)在费托合成制低碳烯烃(Fischer-Tropsch to Olefin, FTO)中起着重要的催化作用。通过X射线衍射(X-ray Diffraction, XRD)、X射线吸收精细结构(X-ray Absorption Fine Structure, XAFS)等表征与方法,对碱金属在CoMn催化FTO中形成碳化钴的影响进行了研究。在钠(Na)、钾(K)元素的影响下,CoMn催化剂在活性评测中,低碳非饱和烃与低碳饱和烃的比例高达17.4与9.4,且仅有较低的甲烷(CH4)产生,而锂(Li)对CoMn催化剂的选择性影响较弱。通过XRD表征,发现Na、K对CoMn催化剂形成Co2C有很好的促进效果。XAFS揭示了CoMn催化剂的电子结构,催化反应后形成碳化钴的配位结构,为研究CoMn催化剂微观结构提供了基础理论。
文摘Three calculational models, statistical associating fluid theory (SAFT), modified SAFT, and Boublík Alder Chen Kreglewshi (BACK) are compared for supercritical CO 2 C 2H 5OH using a set of van der Waals type mixing rules for both the BACK equation of state (EOS) and the SAFT EOS. Equations are presented for the residual Helmholtz free energy, residual chemical potentials, and compressibilty factor for mixtures. A comparison with experimental vapor liquid equilibrium (VLE) data reveals that the BACK EOS together with the suggested mixing rules provides more accurate prediction of the binary system than the SAFT or the modified SAFT model with no adjustable binary parameters. The correlation results are improved with an adjustable parameter.
基金This study was funded by the National Natural Science Foundation of China(Grant No.31470529,31270517)Pandeng Project for Young&Middle-aged discipline leaders of Zhejiang Province(Grant No.pd2013234)Zhejiang Province Key Laboratory for Wood Science and Technology(Grant No.2014lygcy025).
文摘Biochar application to cropland has been recommended as a strategy to reduce increasing at-mospheric CO2 concentrations and mitigate climate change.However,the direction and magnitude of responses of greenhouse gas(GHG)fluxes to biochar application to cropland remain unclear.Our meta-analysis of 296 observations across 61 studies for the first time quantitatively estimated the effects of biochar amendment on fluxes of three GHGsCO2,N2O,and CH4.The results showed that biochar application led to a significant change in soil GHGs emissions:in general,19%for CO2,−16%for N2O(P<0.05),but no pronounced change in CH4 emissions;in paddy,−5%for CO2,−20%for N2O,but+19%for CH4(P<0.05);in upland,−18%for N2O,+12%for CO2,and high uncertainty for CH4.The responses of soil GHG flux-es to biochar application were regulated mainly by experiment length,biochar application rate,biochar properties,providing a new perspective for more comprehensive understanding on biochar.The bio-char derived from husk was recommended to apply to cropland with an application rate of 20-30 t·ha^(−1).
