Preparation Of MnO/Spore-Based Carbon Microspheres Composites For Electrochemical Performance Study

Metal oxide/carbon nanocomposites have been currently promising energy storage materials in supercapacitor electrodes,which cover higher energy density,power density,and cycle stability due to the energy storage mechanism of electric double layer capacitors and pseudocapacitors.However,there are still two problems with metal oxide/carbons nanocomposites,and they need to be paid much attention to:on the one hand,metal oxides for composites are usually low in content and easy to agglomerate.On another hand,the surface of carbon nanomaterials is naturally hydrophobic,resulting in a very limited effective specific surface area,which is still the key problem to be solved in practical applications.In order to solve the mentioned problems,this paper mainly proposes solutions in two aspects.Firstly,the Ganoderma spores in Changbai Mountain are ellipsoidal with double-layered cell wall structure composed of chitin and dextran,the outer shell has naturally formed small holes and the inner cavity is larger,results in biomass carbon prepared by one-step carbonization method.The prepared spore-based porous hollow carbon microspheres have the advantages of regular morphology,good fluidity,good mechanical properties,and easy adjustment.In addition,chitin contained-NH not only can as the nitrogen source precursor,it can also generate a complexation reaction with Mn2+,then generate MnO with good pseudocapacitive properties by the one-step carbonization process.Then,the N/S double-doped carbon material prepared by the heteroatom doping method has good wettability,can provide a larger effective contact area with the electrolyte,and lead to improving the specific capacitance.Compared with the usual wet treatment,the plasma treatment has very short reaction time,and high efficiency.And it usually only acts on the surface of the material,but does not damage or change its internal structure and chemical properties.After the reaction,there is generally no need for purification and impurity removal.Therefore,the treatment is no excess waste and recycling treatment,which meets the green and environment-friendly requirements.The surface performance of carbons can be controlled and optimized by simply adjusting the plasma parameters.Therefore,according the perspective of low cost and environmental friendliness,the composites of biomass-based carbons and MnO were prepared by a simple one-step method,heteroatom doping and plasma treatment.In order to prepare electrode materials with high electrochemical performance,which is applied to supercapacitors with high specific capacitance,fast charge and discharge,and good cycle performance.The main research contents of this article indicate as follows:(1)With using Ganoderma spores as carbon and nitrogen sources,spore-based carbon microspheres were prepared by one-step carbonization,and plasma surface treatment was performed with Ar and O2 to prepare GSC-Ar,GSC-AO,and GSC-O.Among GSC-Ar series samples,the specific capacitance of GSC-Ar-8 is the maximum of 208.63 F g-1 at the current density of 0.5 A g-1,and the minimum resistance of GSC-Ar-4 is 0.4 Ω.Among GSC-AO series samples,GSC-AO-0.2 has the highest specific capacitance of 202.85 F g-1 at the current density is 0.5 A g-1.In GSC-O series samples,the specific capacitance of GSC-O-8 is the maximum of 377.44 F g-1 at the current density of 0.5 A g-1,and the capacitor retention is 98.21%after 10 000 times cycle at the current density of 10 A g-1.(2)With using thiourea as a dopant,N/S double doping was performed on the spore-based carbon microspheres after plasma treatment,according to different mass ratios to prepare GSC-NS and GSC-O-NS.Among GSC-NS series samples,the specific capacitance of GSC-NS-15 is the maximum of 267.47 F g-1 at the current density of 0.5 A g-1,and the capacitor retention is 96.07%after 10 000 times cycle at the current density of 10 A g-1.Among GSC-O-NS series samples,the specific capacitance of GSC-O-NS-15 is up to 222.75 F g-1 at the current density of 0.5 A g-1,and after 10 000 times cycle at the current density of 10 A g-1,the capacitance retention is 94.89%.(3)MnO/GSC-O-8 and MnO/GSC-O-NS series samples were prepared using ganoderma spores as a carbon source by the simple impregnation-carbonization method.MnO/GSC series samples were successfully doped with cubic MnO.The Mn atom content in MnO/GSC-0.7 is 5.15%,and the specific capacitance was the maximum of 354.29 F g-1 at the current density of 0.5 A g-1.The resistance value is 2Ω,and the capacity retention is 62.71%after 10 000 cycles at the current density of 10 A g-1.The specific capacitance of MnO/GSC-O-8 is 362.53 F g-1 at the current density of 0.5 A g-1.The small holes of the outer shell in MnO/GSC-O-NS series sample characterize an octopus sucker-shaped hollow cylinder body,the inner and outer shell thickness is approximately 200 nm,and the hollow inner diameter is 3-5 pm.The specific capacitance of MnO/GSC-O-NS-10 is the maximum of 568.92 F g-1 at the current density of 0.5 A g-1,and the capacity retention is 75.11%after 10 000 cycles at the current density of 10 A g-1.In summary,MnO/spore-based carbon microsphere composites were prepared by Ganoderma spores as the carbon source through plasma treatment and N/S double doping,which can be applied to supercapacitor with high specific capacitance,fast charge/discharge,and good cycle performance.This study provided the effective theoretical guidance for biomass carbon in the application field of electrochemistry.