Synthesis And Characterization Of Multi-layered Nickel Hydroxide Composite And Porous Carbon From Biomass For Energy Storage Application

The high-level consumption of fossil fuel,its effects on the environment,and the rapid decline in fossil fuel is a serious threat worldwide.Inexhaustible research is underway to address these issues,and experts in the field of energy have focused on finding an alternate source of energy,need to be environmentally friendly,cost-effective with a continuous supply of energy.Supercapacitor and batteries technologies have gained great attention for the next generation of renewable energy to supply sustainable energy.Though,the present technologies didn't meet the requirements to supply high and quick energy with conventional fossil fuel.Energy expert is trying to obtain the nanomaterial which has excellent electrochemical performance such as,quick charge dis-charge,long cycle ability,simple preparation,and low cost.Recently the nickel hydroxide based batteries and carbon-based biomass supercapacitor gain great attention due to unique electrochemical applications,low cost of preparation,fast charging-discharging,long cycle life with high current density,and environmental safety.As a result of these unique properties,the Ni-MH batteries and supercapacitors have commercially applied in many appliances,like laptops,calculators,watches,electric vehicles,and hybrid vehicles like Toyota Prius.In this dissertation,we aimed to discuss the synthesis and characterization of composites of nickel hydroxide,growth of different polymorph of nickel hydroxide on nickel foam.The last two parts of this dissertation are focused on the derivation of biomass carbon from a different source and their utilization as a high-performance supercapacitorThe current dissertation is consists of four projects;in the first project,we synthesized the composite of nickel hydroxide with a proper proportion of various polymorphs.We obtained unique spherical morphology with an interesting crystal lattice.The obtained material also exhibits the high specific capacitance up to 452 mAhg-1 of the optimized ratio of various polymorph for Ni-MH batteries at high current density with a 3000 charge dis charge cycle.Furthermore,the nickel foam were used as a substrate.The nickel hydroxide growth with the polymorph by the complexation precipitation reaction with any binder,first we grow the ?-Ni(OH)2 on the nickel foam then and the same time we grow the ?-Ni(OH)2 to protect the surface of ?-Ni(OH)2 from conversion to ?-Ni(OH)2 on the pristine nickel foam.The obtained hierarchical nanosheet material exhibit excellent electrochemical performance,432 mAhg-1,and 357 mAhg-1 at 20 and 100 A g-1.The nanosheets also show a long cycle ability up to 10,000 at 100 A g-1.Moreover,we focused on bio mass carbon from a different natural sources and used as cathode material for supercapacitor.Hence in the fifth chapter of the thesis,we selected the tea as biomass source,carbonized,and activated it with KOH with a 1:2 weight ratio to obtained highly rod-shaped porous carbon for supercapacitor.The obtained porous carbon from biomass has a high pore volume with a surface area of 1610 m2 g-1.It is providing the electrochemical performance up to 332 F g-1 and 222 F g-1 at 1 A g-1 and 100 A g-1,respectively.The obtained porous carbon also provided a long cycle ability up to 100,000 at 100 A-1.In the last chapter of the thesis,we derived the biomass from withered rose and used the obtained material for electrochemical performance.The obtained carbon(denoted as RDPC)by a facile two-step method of carbonization followed by activation with a mixture of KOH/KNO3.The as-derived RDPC contains an enlarged SSA of 1980 m2 g-1,by using the three-electrode system with 6 M KOH electrolyte,the RDPC displays a wonderful electrochemical activity as supercapacitor electrode including of ultrahigh SC(346 F g-1 at 1 A g-1),(165 F g-1 even at 150 A g-1)and remarkable cycle life(remains 95.6%of capacitance after 140,000 cycles at 100 A g-1).As well,the RDPC based symmetrical supercapacitor with 6 M KOH electrolyte supplies the highest energy density of 15.6 Wh kg-1 at 499 W kg-1 with the loss only 3.5%of capacitance over 15,000 cycles at 20 A g-1.This outstanding electrochemical performance of RDPC could be attributed to its uniform wind wave-like morphology,hierarchical porous networks,large specific surface area,and fast electrochemical kinetics.