Synthesis Of Biomass-derived Electrode Materials And Their Supercapacitor Performance

To serve as the most extensively utilized electrode materials for supercapacitors,carbon-based material possesses many advantages,such as long-term cyclic stability,high power density,and fast energy storage and delivery.Biomass-derived carbon-based electrode materials attract extensive attention due to its abundant reserves,wide availability,and low costing.The relatively low specific capacitance of carbon-based electrode materials,however,limited the improvement of the whole supercapacitor device performance and practicability.This work concentrated on the design and synthesis of the biomass-derived porous carbon materials with high specific capacitance.The biomasses,camellia oleifera residue and sodium lignin sulfonate,were introduced as raw materials,and treated in three different ways--high temperature activation,microwave activation and metal catalytic microwave activation,to prepare a series of porous carbon containing abandunt oxygenic functional groups.Furthermore,the relationship between superficial oxygenic functional groups and the performance of the supercapacitor was profoundly investigated.The brief introduction of the work is described as following:1.With camellia oleifera as carbon precursor and potasium hydroxide as activating agent,the porous carbon materials were prepared via three different ways,high temperature activation,microwave activation and activated carbon-assisted microwave activation,respectively.The carbon materials with a high specific surface area of 1726 m2·g-1 and abundant mesopore and micorpore were obtained through experimental condition optimization.The sample prepared by activated carbon-assisted microwave activation was measured by infrared spectroscopy(IR),elemental analysis(EA)and X-ray photoelectron spectroscopy(XPS)characterizations.The results show that the proportion of oxygen is 14.9 wt.%in which C=O accounted for 51.6 mol.%.The oxygenic functional groups,especially the carbonylic groups,can not only improve the hydrophilic property of the materials,but also contribute to the psudocapacitance of the materials in acidic electrolyte solution,which further increases the specific capacitance of the materials.The results of electrochemical tests show that in the 2 mol·L-1 sulfuric acid solution the carbon material treated by activated carbon-assisted microwave activation exhibit the specific capacitance of 518 F·g-1 at the current density of 0.5 A·g-1.What’s more,after 10000 charge-and-discharge cycles at 10 A·g-1.the specific capacitance of that could completely remain its original value.These results suggested that carbon material treated by microwave activation has high capacity and excellent cycle stability,indicating the potential application of the camellia oleifera-derived porous carbon in the electrochemical energy storage device.2.By using sodium lignin sulfonate as carbon precursor and potasium hydroxide as activating agent,the porous carbon materials were prepared via two different ways,high temperature activation and microwave activation,respectively.The carbon materials with relatively high specific surface area and abundant mesopore and micorpore were obtained through experimental condition optimization.The sample treated by microwave activation the proportion of oxygen is 26.8 wt.%in which C=O possesses 49.0 mol.%.The results of electrochemical tests show that the carbon material treated by microwave activation exhibit a specific capacitance of 300 F·g-1 at 0.5 A·g-1 in the 2 moL·L-1 sulfuric acid solution.Moreover,after 10000 charge-and-discharge cycles,the specific capacitance could still retain 79%of its original value at the current density of 20 A·g-1.3.The sodium lignin sulfonate was loaded by the nickel acetate tetrahydrate via incipient immersion and the mixture was then pretreated under the inert atmosphere.After that,the microwave activation was employed to obtain the highly graphitized carbon material with the tube-like morphology.X-ray diffraction(XRD)analysis and X-ray photoelectron spectroscopy(XPS)characterization proved that this kind of material was not only highly graphitized but rich in surface oxygenic functional groups.Actually,in the 2 mol·L-1 sulfuric acid solution,the material shows specific capacitances of 268 F·g-1 at the current density of 0.5 A·g-1 and 191 F·g-1 at the current density of 30 A·g-1.Then,after 10000 charge-and-discharge cycles,the specific capacitance of the material could retain 92%at 10 A·g-1.