Facile Synthesis of Highly Porous N-Doped Carbon Nanosheets with Silica Nanoparticles for Ultrahigh Capacitance Supercapacitors

Abstract

Low-cost, scalable, and abundant biomass-derived carbon materials have attracted considerable attention. Herein, we report on novel self-doped (nitrogen) porous carbon nanosheets by carbonization/activation of acorn shells as a biomass precursor for use in high-performance supercapacitors (SCs), which contain SiO2 nanoparticles embedded in carbon nanosheets. This oaknut shell-based activated carbon (AOC) generates an ultrahigh surface area of 3757 m2 g–1, with micropore–mesopore distribution and formation of moderately graphitized sp2 carbon structures. The AOC electrode delivers an impressive specific capacitance of 505 F g–1 at 1.6 A g–1 in three-electrode systems, which is higher than the reported biomass-derived electrodes so far. Further, the symmetric SC displays a remarkable specific energy of 12.7 W h kg–1 at a specific power of 200 W kg–1 in neutral electrolytes, exhibiting high rate capability and retaining 96% of capacitance compared to commercial activated carbon. The outstanding electrochemical performance of the electrode can be ascribed to the large surface area with optimum pore tortuosity for ion transport, high electrical conductivity, and presence of self-doped heteroatoms. Overall, we believe that this high-specific energy self-doped tunable porous carbon can be utilized for industrial SCs.

Hierarchical Architectured Dahlia Flower-Like NiCo2O4/NiCoSe2 as a Bifunctional Electrode for High-Energy Supercapacitor and Methanol Fuel Cell Application

“…Three-electrode and two-electrode cells were used for supercapacitor measurements in 6 M KOH as supporting electrolytes at potential windows from 0 to 0.5 V. The two-electrode hybrid device was assembled using NCO/ NCS/NF and oak nutshell-derived porous activated carbon (O-AC) coated onto NF. The preparation of the O-AC electrode 3 and calculations of specific capacitance and energy/power densities are given in the Supporting Information (SI).…”

“…1,2 Among the various energy storage systems, supercapacitors have gained great interest in various fields due to their long cyclic life, high specific power, rapid charge transfer rate, and safety. 3 However, they suffer from low specific energy compared to batteries and fuel cells, restricting their industrial applications. The specific energy of supercapacitors depends on the capacitance and operating potential (E = 1/2 CV 2 ).…”

“…With fossil fuel exhaustion, environmental pollution, and huge energy demand due to rapid population growth, there exists a critical challenge toward the development of sustainable energy storage/conversion systems. , Among the various energy storage systems, supercapacitors have gained great interest in various fields due to their long cyclic life, high specific power, rapid charge transfer rate, and safety . However, they suffer from low specific energy compared to batteries and fuel cells, restricting their industrial applications.…”

KOH Chemical-Activated Porous Carbon Sponges for Monolithic Supercapacitor Electrodes

“…The preparation of porous carbon materials usually involves two steps: carbonization and activation. Various carbon sources are first carbonized at high temperature, and then physical activation (usually in steam, oxygen, and carbon dioxide atmospheres) or chemical activation (e.g., potassium hydroxide, phosphoric acid, and zinc chloride) is utilized to improve the inner porosity of the carbon materials as well as their surface area. − In particular, KOH activation is widely applied to activate carbon precursors including fossil/biomass waste-derived materials and organic polymers, and then the porosity, specific surface area, and surface functional groups of the obtained carbon materials can be modulated by varying the activation parameters (e.g., amount of activator, target temperature, and treatment time). ,− It should be noted that chemical activation endows carbons with high specific surface area, which contributes to the electric double-layer capacitance (EDLC); meanwhile, the introduced heteroatoms during the activation process can also improve the wettability and provide extra pseudo-capacitance (PC) by redox reactions. , Recently, Dunn et al developed a voltammetric method to separate the redox-related PC contribution from the diffusion-controlled EDLC, which benefits to explore the charge storage mechanism in supercapacitors. , …”

Milling Time-Dependent Lithium/Sodium Storage Performance of Carbons Synthesized by a Mechanochemical Reaction

“…The wide applications of carbon materials are attributed to their tunable morphology and microstructure, , which are mainly determined by the synthetic methods and carbon precursors. Till now, carbon materials with various morphology and microstructure have been successfully synthesized by using a variety of methods, including molten salt electrolysis, etching carbides, heating carbonization, hard or soft template method, etc. − Thereinto, template carbonization of precursors is one of the most popular methods to synthesize porous carbon. Organic compounds such as macromolecular polymers, metal–organic frameworks, and biomass materials have been studied as the main precursors in the synthesis of novel carbons. − Numerous pores are generated in carbon on account of the gas blowing effect in the thermal decomposition of organic compounds.…”