Hole Defects and Nitrogen Doping in Graphene: Implication for Supercapacitor Applications

Abstract

One great challenge for supercapacitor is to achieve high energy capacity and fast charge/discharge rates simultaneously. Porous graphene with large surface area is a promising candidate for electrode materials of supercapacitor. Using first-principles calculations and non-equilibrium Green's function technique, we have explored the formation energies, mechanical properties, diffusion behaviors and electrical conductance of graphene sheets with various hole defects and/or nitrogen doping. Interestingly, graphene sheets with pyridinic-like holes (especially hexagonal holes) can be more easily doped with nitrogen and still retain the excellent mechanical properties of pristine graphene that is beneficial for the long cycle life. Porous graphene electrode with moderate hole diameter of 4.2-10 Å facilitates efficient access of electrolyte and exhibit excellent rate capability. In addition, doping with nitrogen as electron donors or proton attractors leads to charge accumulation and generates higher pseudocapacitance. Transmission coefficients of N-doped graphene sheets with pyridinic-like holes are only moderately reduced with regard to that of pristine graphene and are insensitive to the detailed geometry parameters. Overall, N-doped graphene with pyridinic-like holes exhibits exciting potentials for high performance energy storage in supercapacitor devices.

Raman and Conductivity Analysis of Graphene for Biomedical Applications

“…Consequently, it has been investigated as a feasible candidate for use in device fabrication in numerous areas: electronics [2,3,4,5,6,7,8,9,10], optics [11,12], photonics [3,13], micro/nano-mechanics [14,15,16], and, recently, biomedical engineering [17,18,19,20]. As a two-dimensional material, graphene shows very good thermal and electrical conductivities, which, combined with its unique optical properties, make it suitable for a variety of applications [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]. Many efforts have been made in the last decade related to the conductivity of graphene—in finding accurate measuring methods, as well as in fabricating new graphene-based materials with improved performance [23,24,25].…”

Selective C−C Coupling by Spatially Confined Dimeric Metal Centers

“…Specifically, 4N-V2, 5N-V3 and 6N-V4 systems can be viewed as four, five and six N atoms decorating the edges of divacancy, tri-vacancy and tetra-vacancy in graphene, respectively, all of which have been commonly observed in experiment (Lin et al, 2015;He et al, 2014;. Note that, the V6 pore in graphene is a favorable defect according to transmission electron microscopy experiment (Robertson et al, 2015), and our previous calculation showed that N-doped V6 (namely 6N-V6) has extraordinary thermodynamic stability (Luo et al, 2013). Besides the N-doped graphitic sheets, we also considered the synthetic carbon nitride monolayers, including g-C3N4 and C2N (Zhao et al, 2014;Mahmood et al, 2015).…”

Flexible Asymmetric Supercapacitors Based on Nitrogen‐Doped Graphene Hydrogels with Embedded Nickel Hydroxide Nanoplates

“…Nitrogen doping results in higher positive charges on a carbon atom adjacent to the doped nitrogen atoms. [22,23] Therefore, heteroatom nitrogen doping is an effective approach to enhance the capacitive performance of G. [24,25] To further improve specific capacitance, many efforts have been made to composite G hydrogels with other pseudocapacitive materials such as Ni(OH) 2 , which has been used often because of its high pseuTo push the energy density limit of supercapacitors (SCs), new electrode materials with hierarchical nano-micron pore architectures are strongly desired. Graphene hydrogels that consist of 3 D porous frameworks have received particular attention but their capacitance is limited by electrical double layer capacitance.…”