The low cost and highly efficient construction of electrocatalysts has attracted significant attention owing to the use of clean and sustainable energy technologies.In this work,cobalt nanoparticle decorated N-doped c...The low cost and highly efficient construction of electrocatalysts has attracted significant attention owing to the use of clean and sustainable energy technologies.In this work,cobalt nanoparticle decorated N-doped carbons(Co@NC)are synthesized by the pyrolysis of a cobalt covalent organic framework under an inert atmosphere.The Co@NC demonstrates improved electrocatalytic capabilities compared to N-doped carbon without the addition of Co nanoparticles,indicating the important role of cobalt.The well-dispersed active sites(Co-Nx)and the synergistic effect between the carbon matrix and Co nanoparticles greatly enhance the electrocatalytic activity for the oxygen reduction reaction.In addition,the Co content has a significant effect on the catalytic activity.The resulting Co@NC-0.86 exhibits a superb electrocatalytic activity for the oxygen reduction reaction in an alkaline electrolyte in terms of the onset potential(0.90 V),half-wave potential(0.80 V)and the limiting current density(4.84 mA·cm^(−2)),and a high selectivity,as well as a strong methanol tolerance and superior durability,these results are comparable to those of the Pt/C catalyst.Furthermore,the superior bifunctional activity of Co@NC-0.86 was also confirmed in a home-built Zn-air battery,signifying the possibility for application in electrode materials and in current energy conversion and storage devices.展开更多
Recent progress of Web 2.0 applications has witnessed the rapid development of microblog in China, which has already been one of the most important ways for online communications, especially on sharing information. Th...Recent progress of Web 2.0 applications has witnessed the rapid development of microblog in China, which has already been one of the most important ways for online communications, especially on sharing information. This paper tries to make an in-depth investigation on the big data modeling and analysis of microblog ecosystem in China by using a real dataset containing over17 million records of SinaWeibo users. First, we present the detailed geography, gender, authentication, education and age analysis of microblog users in this dataset. Then we conduct the numerical features distribution analysis, propose the user influence formula and calculate the influences for different kinds of microblog users. Finally, user content intention analysis is performed to reveal users most concerns in their daily life.展开更多
基金supported by the National Natural Science Foundation of China (No.21473167 and No.21688102)the National Key Research and Development Program of China (No.2016YFA0200604)+1 种基金the Fundamental Research Funds for the Central Universities (WK3430000005,WK2340000065)the China Scholarship Council (CSC) (No.201706345015)
基金supported by the Natural Science Foundation of Shandong Province(Grant No.ZR2019PB013)the Training Program of Innovation and Entrepreneurship for Undergraduates(Grant No.CXCY2021161)+1 种基金the Natural Science Foundation of Tianjin(Grant No.19JCZDJC37700)the National Natural Science Foundation of China(Grant No.21875118).
文摘The low cost and highly efficient construction of electrocatalysts has attracted significant attention owing to the use of clean and sustainable energy technologies.In this work,cobalt nanoparticle decorated N-doped carbons(Co@NC)are synthesized by the pyrolysis of a cobalt covalent organic framework under an inert atmosphere.The Co@NC demonstrates improved electrocatalytic capabilities compared to N-doped carbon without the addition of Co nanoparticles,indicating the important role of cobalt.The well-dispersed active sites(Co-Nx)and the synergistic effect between the carbon matrix and Co nanoparticles greatly enhance the electrocatalytic activity for the oxygen reduction reaction.In addition,the Co content has a significant effect on the catalytic activity.The resulting Co@NC-0.86 exhibits a superb electrocatalytic activity for the oxygen reduction reaction in an alkaline electrolyte in terms of the onset potential(0.90 V),half-wave potential(0.80 V)and the limiting current density(4.84 mA·cm^(−2)),and a high selectivity,as well as a strong methanol tolerance and superior durability,these results are comparable to those of the Pt/C catalyst.Furthermore,the superior bifunctional activity of Co@NC-0.86 was also confirmed in a home-built Zn-air battery,signifying the possibility for application in electrode materials and in current energy conversion and storage devices.
基金supported by National Natural Science Foundation of China(No.61272362)National Basic Research Program ofChina(973 Program)(No.2013CB329606)High-Tech Development Plan of Xinjiang(No.201212124)
文摘Recent progress of Web 2.0 applications has witnessed the rapid development of microblog in China, which has already been one of the most important ways for online communications, especially on sharing information. This paper tries to make an in-depth investigation on the big data modeling and analysis of microblog ecosystem in China by using a real dataset containing over17 million records of SinaWeibo users. First, we present the detailed geography, gender, authentication, education and age analysis of microblog users in this dataset. Then we conduct the numerical features distribution analysis, propose the user influence formula and calculate the influences for different kinds of microblog users. Finally, user content intention analysis is performed to reveal users most concerns in their daily life.
