Application Of Biomass-based Carbon Materials In Electrochemical Energy Storage And Electrocatalysis

Biomass,the organisms formed by the transformation of carbon dioxide under photosynthesis,possess the advantages of abundant sources,natural regeneration and low price.Promoting the efficient,diversified and sustainable utilization of biomass resources helps to achieve"carbon peaking and carbon neutrality goals"and environmental protection.Biomass-derived carbon materials have natural and orderly pore structure and abundant heteroatoms（N,O,S,P,etc.）-containing functional groups,which meet the requirements of electrochemical reaction for ion diffusion,storage and conversion,and are widely applied in batteries,supercapacitors（SC）,electrocatalytic oxygen reduction reaction（ORR）,etc.Adjusting the type and content of heteroatoms can not only regulate the physical and chemical properties of biomass-derived carbon materials,but also improve their electrochemical performance.In this paper,heteroatom-doped porous carbon materials were prepared by using sodium lignosulfonate and agar as biomass precursors and applied in the fields of microsupercapacitors（MSC）,dual-ion battery-supercapacitors hybrid devices（DIB-SCHD）and ORR.The main research contents are as follows:（1）With sodium lignosulfonate,melamine sponge and potassium hydroxide as raw material,template and activator,respectively,N,S co-doped porous carbon-based inks with excellent capacitive were prepared by spraying,carbonization and ball milling process.Based on screen printing technique,planar micro-supercapacitors with interdigital and stripe patterns were successfully constructed.The output voltage and capacitance of micro-supercapacitor could be accurately regulated by changing the number of series and parallel connection.In addition,the device has excellent mechanical stability and shape diversity.This strategy provides a new solution towards low-cost and scalable electrochemical energy storage devices,which can be applied to wearable and intelligent electronic devices,micro sensors,electric vehicles and industrial power management.（2）Agar was served as raw material.Nitrogen doped microporous dominant carbon（N-MPC）was prepared by sol-gel method.Based on Li Cl/EMIMBF₄ dual-salt electrolyte,a dual-ion battery-supercapacitors hybrid device（DIB-SCHD）was developed.The device cleverly integrating a dual-ion battery（DIB）and a supercapacitor（SC）,is expected to endow both the high energy density of dual-ion battery and the high power density of supercapacitor.Benefitting from the similar features of the electrolyte and symmetrical electrode configuration,a state-of-the-art DIB-SCHD delivers an ultra-high mass specific capacitance of 374 F g^-1 with a high voltage of 3.5 V and presents a very high specific energy of 208 Wh kg^-1 at 1144 W kg^-1 and outputs ultrahigh power density of 22834 W kg^-1 at 77 Wh kg^-1.The perfect integration of the dual-ion battery-type and supercapacitor-type electrodes provides a new strategy toward high energy and power density electrochemical energy storage devices.（3）By using sodium lignosulfonate as the sources of carbon and sulfur elements,melamine sponge as template,and potassium hydroxide as pore-making reagent,N,S co-doped carbon materials with excellent ORR catalytic performance were developed through tuning the pre-carbonization temperature and carbonization temperature.The two-electron and four-electron pathways of electrocatalytic ORR can be regulated by changing the calcination temperature.The carbon material of KNSC-350-0 shows a high selectivity of 88%toward H₂O₂ at 0.4 V（vs.RHE）and the corresponding electron transfer numbers is 2.2.An early onset potential is 0.783V at a current density of 0.1 m A cm^-2.The carbon material of KNSC-550-800 only presented a selectivity of 15%toward H₂O₂ at 0.4 V（vs.RHE）and electron transfer numbers of 3.7.The limiting diffusion current density reached 5.27 m A cm^-2 with half wave potential of 0.84 V.Control experiments and characterization demonstrated benzothiophene sulfone contributed to the two-electron ORR pathway,while benzothiophene sulfone and benzothiophene sulfoxide together were related to the four-electron ORR pathway.