| As one of the most important members of carbon fibers,carbon nanofiber(CNF)has low density,low defect,high porosity,high specific surface area,good mechanical properties and excellent electrical conductivity.Therefore,CNF has displayed great potentials in many fields,such as electrical devices,electrode materials of rechargeable batteries and supercapacitors,and chemical sensors.However,CNF is mainly synthesized by the pyrolysis of synthetic polymers,such as polyacrylonitrile,polyimide,and polyvinyl alcohol.With the ever-changing global climate and the emergence of resource shortages,the current synthesis pathway is hard to meet people for the demands of high-performance,environmentally friendly materials.Bacterial cellulose,as a controllable biomass material,can be used as an alternative to synthetic polymers.However,the method of the preparation of bacterial cellulose is very complicated,time-consuming and costly,which hindered its industrial production and application.In this paper,cellulose nanofibers with different sizes were fabricated by simple and controlled mechanical treatment of bleached bamboo pulp.Then,porous nano-carbon materials with high specific surface area were obtained through pyrolysis of cellulose nanofibers.The electrochemical properties of carbon nanofibers were studied by zinc air batteries(ZABs)and lithium ion batteries(LIBs).Thus,this article contains following aspects of research work.(1)The ultrathin nanometer cellulose nanoribbons(Cel-NRs)with tunable thickness was delaminated from bleached bamboo pulps with combining TEMPO-mediated oxidation and successive high-frequency ultra-sonication treatment.And the TEMPO molecules entrance into elementary fibrils along cellulose I(101)plane to selectively oxidize C6-hydroxyl groups and break(200)intra-plane hydrogen bonds.The Cel-NRs precursor has unique morphology,which ensured high-containing active sites as well as superior mass and charge transport of N-CNRs for ORR after the thermal transformation in NH3.As a result,the morphology-preserved N-doped carbon nanoribbons(N-CNRs)were exemplifying the feasibility for practical applications as a promising low-cost,highly efficient air cathode in primary metal-air batteries.The atomically thin N-CNRs features high-density N-doped active sites(10.6 at%)and unique super-thin nanoarchitecture,making them exhibit good activity and superb stability for ORR in the basic media.When used in Zn-air battery as the air-cathode,the atomically thin N-CNRs exhibit a high voltage of 1.18 V,a comparable specific capacity of 590 mAhgZn-1,and extraordinary stability of 50 h at discharge densities of 20 mA cm-2.The stability of atomically thin N-CNRs exceeds those of the NH3-actived carbon nanotubes and the conventional Pt/C catalyst.(2)Renewable nanofibers of cellulose(NFC)with tunable diameters which were extracted from bamboo pulps by high frequency ultrasound and subsequent selective oxidation,was assembled into 3D aerogel framework with controllable structure.After carbonization in ammonia gas and potassium hydroxide(KOH)activation,nitrogen-doped porous carbon nanofiber(N-ACNF)aerogels with 3D hierarchical porous structure were obtained.The obtained N-ACNF has high surface area to volume ratio,high porosity,excellent mechanical properties and good conducting connectivity.The unique structure of the interconnected 3D porous structure of aerogel and the 1D building blocks of nanofibers can provide multiple pathways for Li ions and charge transport,making it outperform other carbon based batteries.When evaluated as anode materials for LIBs,the N-ACNF aerogels showed outstanding cycling stability,high capacity,and good rate performance.For instance,the NACNF-50 aerogel with 1D CNF diameter of 50 nm exhibited the highest capacity of 630.7 mAh g-1 at 1 A g-1,the best rate capability(289 mAh g-1 at 20 A g-1)and cycling performance(651 mAh g-1 at 1 A g-1 after 1000 cycles). |
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