Preparation,Structure Design And Electrochemical Application Of Heteroatom Doped Hierarchically Nanocarbon Materials

With the rapid development of the global economy,rapid depletion of fossil fuels and increasingly worsening environmental pollution,there is an ever-increasing demand for sustainable and renewable power sources,which has stimulated intensive research on efficient,clean energy conversion and storage devices to meet urgent future energy requirements worldwide.Electrochemical water splitting is widely considered to be a critical step for efficient renewable energy production,storage and usage including sustainable hydrogen production,rechargeable metal-air batteries and fuel cells.Currently,Ir-and Ru-based compounds play as stadard catalysts toward the oxygen evolution reaction(OER),while platinum group metals are most efficient hydrogen evolution reaction(HER)catalysts.However,both types of systems suffer from metal scarcity and high costs,limiting their widespread use.A great deal of effort and progress has been made in recent years towards the development of efficient OER and HER catalysts with earth-abundant materials,such as transition metal phosphate or oxides or and hydroxides for OER,and chalcogenides or carbides or phosphides for HER.However,pairing the two electrode reactions together in an integrated electrolyser for practical use is difficult due to the mismatch of pH ranges in which these catalysts are stable and remain most active.Furthermore,these materials have generally low electronic conductivity,limiting their potential in electrocatalysis enhancement.Developing efficient and low-cost full water splitting catalysts working at all pH values remain highly challenging.Various heteroatom doped carbon materials feature unique advantages for designed water splitting electrocatalysis due to their tunable molecular structures,abundance and strong tolerance to acid/alkaline environments.Aqueous supercapacitors were among the most promising techniques for clean and renewable energy storage yet limited by their low specific energy arisen from water splitting issue as well.Carbonaceous materials have been widely adjusted into broad applications in the fields of energy conversion and storage.Their high adjustability in terms of composition,porosity,infrastructure,and morphology makes carbonaceous materials extremely favourable for supercapacitor electrode materials.Based on issue and advantages analysed above,I summarize the developments of non-metal carbon nanomaterial used for HER,OER and supercapacitor first.Then I design and fabricate N doped hierarchically porous carbon nanomaterial used for HER and OER.Also I design and fabricate low heteroatom doping content and hierarchically porous carbon nanomaterial used for water supercapacitors.The following is the content in detail and the achieved results:1.We use NaNH2 and PVDF as reagents to fabricate material with carbonation using ball milling strategy.The as prepared carbonized material are then calcinated for further graphitization under inert gases and pore size abundant heriachically.As BET characterization result,samples with melamine possess greater specific surface area,larger than 1300 m2/g for all,and NaNH2+Mela-8 have highest SSA as large as 1498.3 m2/g which is dominated by micro-pore and meso-pore.Also melamine acts as another dopant for N doping.Good structure and better doping effect do good for HER/OER catalyst.As lineare scan voltage results show,NaNH2+Mela-8 are relatively more effective than other 5 samples.The way of ball milling in room temperature is facile and easy to repeat,in this way,the material are feasible to produce in a large scale for any other usage.2.Dehalogenation strategy was developed to fabricate hierarchically porous carbon materials with minor functionality and dopant.These superb carbon materials were systematically investigated by electrochemistry where water-splitting-inactive electrode materials were fully revealed.The as-assembled super-capacitor can realized a 2.5 V stable potential window in neutral Li2SO4 solution.Symmetric super-capacitor device could provide superior EDL and OER-free behavior under a high OCV of 2.0 V.Moreover,the superior durability of only 6%loss of the initial capacitance has been demonstrated through 5,000 cycle electrochemical test at 5.0 A/g.We believe that the proposed dehalogenation strategy associate with non-active nature of water splitting reaction provides an unprecedented opportunity to realize the large window aqueous super-capacitor with prompted specific energy density.