Abstract In the field of polymer/graphene nanocomposites, massive production and commercial availability of graphene are essential. Exfoliation of graphite to obtain graphene is one of the most promising ways to large...Abstract In the field of polymer/graphene nanocomposites, massive production and commercial availability of graphene are essential. Exfoliation of graphite to obtain graphene is one of the most promising ways to large-scale production at extremely low cost. In this work we illustrate a facile strategy for mass production of few-layered （≤ 10） graphene （FLG） via the newly explored ball milling. The achieved FLG concentration was determined by UV/Vis spectroscopy. The formation of FLG was proved by measuring the flake thickness by atomic force microscopy （AFM）. Further Raman spectral studies indicated that the crystal structure of exfoliated flakes was preserved satisfactorily during this shear-force dominating process. To increase the maximum concentration obtainable, it＇s critical to make a good parameter assessment. N-methylpyrrolidone （NMP） was used as a dispersing medium and the effect of milling parameters was systematically and quantitatively investigated, thus providing a criterion to optimize the milling process. We established the optimal values for solvent volume and initial weight of graphite. As for milling time, the production of FLG was enhanced with continuous milling according to the power law, but not linearly with increasing milling time. Moreover, the possible mechanism involved in milling process was also explored. Our work provides a simple method for graphite exfoliation and has great potential for improving thermal and electrical conductivity of polymer composites in the fields of engineering.展开更多
LiBH_(4) has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity,which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversio...LiBH_(4) has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity,which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversion via anodic oxidation reaction of direct borohydride fuel cells(DBFCs).However,the realization of practical hydrogen applications heavily depends on the effective synthesis of high-purity LiBH_(4) and recycling of the spent fuels(LiBO_(2)·xH_(2)O).The present work demonstrates a convenient and high-efficiency solvent-free strategy for regenerating LiBH_(4) with a maximum yield close to 80%,by retrieving its by-products with MgH_(2) as a reducing agent under ambient conditions.Besides,the hydrogen released from the regeneration course can completely compensate the demand for consumed MgH_(2).The isotopic tracer method reveals that the hydrogen stored in LiBH_(4) comes from both MgH_(2) and coordinated water bound to LiBO_(2).Here,the expensive MgH_(2) can be substituted with the readily available and cost-effective MgH_(2)-Mg mixtures to simplify the regeneration route.Notably,LiBH_(4) catalyzed by CoCl_(2) can stably supply hydrogen to proton exchange membrane fuel cell(PEMFC),thus powering a portable prototype vehicle.By combining hydrogen storage,production and utilization in a closed cycle,this work offers new insights into deploying boron-based hydrides for energy applications.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51421061 and 51210005)Guangdong Shengyi Technology Limited Corporation
文摘Abstract In the field of polymer/graphene nanocomposites, massive production and commercial availability of graphene are essential. Exfoliation of graphite to obtain graphene is one of the most promising ways to large-scale production at extremely low cost. In this work we illustrate a facile strategy for mass production of few-layered （≤ 10） graphene （FLG） via the newly explored ball milling. The achieved FLG concentration was determined by UV/Vis spectroscopy. The formation of FLG was proved by measuring the flake thickness by atomic force microscopy （AFM）. Further Raman spectral studies indicated that the crystal structure of exfoliated flakes was preserved satisfactorily during this shear-force dominating process. To increase the maximum concentration obtainable, it＇s critical to make a good parameter assessment. N-methylpyrrolidone （NMP） was used as a dispersing medium and the effect of milling parameters was systematically and quantitatively investigated, thus providing a criterion to optimize the milling process. We established the optimal values for solvent volume and initial weight of graphite. As for milling time, the production of FLG was enhanced with continuous milling according to the power law, but not linearly with increasing milling time. Moreover, the possible mechanism involved in milling process was also explored. Our work provides a simple method for graphite exfoliation and has great potential for improving thermal and electrical conductivity of polymer composites in the fields of engineering.
基金This work was financially supported by the National Natural Science Foundation of China Projects(Nos.51771075)the National Key R&D Program of China(No.2018YFB1502101)+2 种基金the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.NSFC51621001)by the Project Supported by Nat-ural Science Foundation of Guangdong Province of China(2016A030312011)Shao acknowledges support from Macao Science and Technology Development Fund(FDCT)(Project No.:0062/2018/A2 and 0019/2019/AGJ).
文摘LiBH_(4) has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity,which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversion via anodic oxidation reaction of direct borohydride fuel cells(DBFCs).However,the realization of practical hydrogen applications heavily depends on the effective synthesis of high-purity LiBH_(4) and recycling of the spent fuels(LiBO_(2)·xH_(2)O).The present work demonstrates a convenient and high-efficiency solvent-free strategy for regenerating LiBH_(4) with a maximum yield close to 80%,by retrieving its by-products with MgH_(2) as a reducing agent under ambient conditions.Besides,the hydrogen released from the regeneration course can completely compensate the demand for consumed MgH_(2).The isotopic tracer method reveals that the hydrogen stored in LiBH_(4) comes from both MgH_(2) and coordinated water bound to LiBO_(2).Here,the expensive MgH_(2) can be substituted with the readily available and cost-effective MgH_(2)-Mg mixtures to simplify the regeneration route.Notably,LiBH_(4) catalyzed by CoCl_(2) can stably supply hydrogen to proton exchange membrane fuel cell(PEMFC),thus powering a portable prototype vehicle.By combining hydrogen storage,production and utilization in a closed cycle,this work offers new insights into deploying boron-based hydrides for energy applications.
