Nitrogen Co-doped Graphene Aerogel Research Articles

Cost effective synthesis of sulfur and nitrogen co-doped graphene aerogel and application in binder free supercapacitor

Incorporating heteroatoms into graphene lattice results in enhanced electrical conductivity and electrochemically active sites and has significant importance in developing high-performance supercapacitors. In this study, sulfur and nitrogen co-doped graphene aerogel is synthesized via hydrothermal technique followed by a simple but effective freeze-thawing and ambient pressure drying process (referred to as SN-GA). The process requires low-cost raw materials and cost-effective equipment without the utilization of any special instrument that operates at ultra-low temperatures, under high pressure, or vacuum environment. Ammonium sulfate [(NH4)2SO4] and ethylenediamine are used as a source of sulfur and nitrogen and as a reducing agent. (NH4)2SO4 with different molarities (0, 12, 24, and 36 mM) are used to synthesize four different aerogel samples marked as GA, SN-GA1, SN-GA2, and SN-GA3. The electrode is prepared using an SN-GA2 sample, exhibiting an outstanding specific capacitance of 244 F g−1 at an applied current density of 1 A g−1 with almost 98.5% Coulomb efficiency. Furthermore, based on the SN-GA2 sample, the symmetrical supercapacitor is fabricated, displaying an energy density of 18.14 Wh kg−1 at a power density of 498.4 W kg−1. Hence, SN-GA2 renders a promising material for supercapacitor applications.

Sulfur and nitrogen co-doped three-dimensional graphene aerogels for high-performance supercapacitors: A head to head vertical bicyclic molecule both as pillaring agent and dopant

The two-dimensional (2D) graphene sheets can be self-assembled into three-dimensional (3D) graphene aerogels by a typical hydrothermal route to improve the supercapacitor performance in recent years. The novelty of this paper is that we use 5-mercapto-3-phenyl-1,3,4-thiadiazole-2(3H) thione potassium salt (BII) as pillaring agent and dopant to synthesize 3D sulfur and nitrogen co-doped graphene aerogel (SNGA) as supercapacitor electrode materials. It is noteworthy that BII is a vertical bicyclic molecule with a special head-to-head non-planar structure effectively inhibiting the close stacking of graphene sheets during the self-assembly process. Therefore, SNGA4 synthesized under optimal condition obtains a larger specific surface area (410.2 m2 g−1). At the same time, BII with rich sulfur and nitrogen promote the doping amount of sulfur atoms at 3.71 at.% via the supramolecular interactions (π-π interaction and hydrogen bonding). In the three-electrode configuration, the capacitance reached 399F g−1 (current density is 1 A g−1), and the energy density gained 11.36 Wh kg−1 in the assembled supercapacitor system. These results indicate the great potential of SNGA4 as an electrode material for supercapacitors. Furthermore, this work gives us a deeper understanding of how to choose pillaring agents and dopants in the fabrication of high-performance graphene-based supercapacitor electrodes.

One-pot hydrothermal preparation of B and N co-doped graphene aerogels loaded with cobalt oxides for the synergistic enhancement of oxygen reduction electrocatalysis

Developing non-precious metal catalysts with superior activity and stability for the oxygen reduction reaction (ORR) remains challenging for application of full cells. In this work, three-dimensional boron and nitrogen co-doped graphene aerogels loaded with cobalt oxides (3D BNGCo) catalysts were designed and prepared by a one-pot hydrothermal method. In this 3D nanoarchitecture, CoOx nanoparticles were evenly spread over the BNG surface without aggregation. As a non-precious metal cathode electrocatalyst, the 3D BNG-Co catalyst favors a direct 4e− pathway and exhibits excellent activity towards ORR, as well as superior long-term durability. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the ORR reach −0.02 V (vs. Ag/AgCl), −0.3 V (vs. Ag/AgCl) and 5.6 mA cm−2, which are comparable to those of commercial 20 wt% Pt/C catalyst. The good electrochemical activities of the as-fabricated catalyst could be attributed to the 3D network foam, unique electronic structure, and the synergy effect of pyridinic N together with BC3 phases. The present work sheds insights into the effects of diatomic doping of the 3D graphene-based nanostructures in the field of ORR and and can be extended to other catalytic systems.

Efficient removal of bisphenol A and disinfection of waterborne pathogens by boron/nitrogen codoped graphene aerogels via the synergy of adsorption and photocatalysis under visible light

It is widely acknowledged that doping of carbon materials by multi-elements with different electronegativities can result in unique electron-donor properties and novel functionalities because of the strong synergistic interaction among the dopant atoms. In this study, boron and nitrogen codoped graphene aerogels (BNGAs) are synthesized and their photocatalytic activity towards decomposition of bisphenol A (BPA) under visible light irradiation is systematically examined. The BPA molecules are rapidly adsorbed onto the 3D interconnected pore system of the BNGAs under dark conditions, and eventually mineralized upon exposure to visible light, indicating the synergy between adsorption-enrichment and photocatalysis during degradation of BPA. Notably, almost 96 % of BPA is removed and over 88 % of total organic carbon is eliminated by the as-prepared BNGAs. More importantly, the BNGAs can retain approximately 92 % of their initial activity even after repeated cycling. In addition, the BNGAs display great potential for the disinfection of harmful pathogens like Escherichia coli, with a photocatalytic decontamination rate of 1.2 × 103 CFU h−1 gcat−1. In view of their attractive multi-functional performance, the as-developed BNGAs merit further consideration for eliminating emerging organic contaminants and pathogens from freshwater sources.

Anchoring nanosized Pd on three-dimensional boron- and nitrogen-codoped graphene aerogels as a highly active multifunctional electrocatalyst for formic acid and methanol oxidation reactions

A facile and scalable strategy is developed for the preparation of nanosized Pd crystals anchored on 3D B- and N-codoped graphene aerogels, which show multifunctional electrocatalytic ability.

High efficient adsorption and storage of iodine on S, N co-doped graphene aerogel.

High efficient adsorption of radioiodine in nuclear waste has attracted extensive attentions all over the world. In this work, we fabricated sulfur and nitrogen co-doped graphene aerogels (SN-GA) through one-step hydrothermal method, and investigated its iodine adsorption behavior including adsorption kinetics and isotherms in water. Our results reveal that SN-GA exhibits a 3D porous architecture with thiophene-S, oxidized-S, pyridine-N, pyrrole-N and graphite-N co-doped into the sp2 carbon frameworks. The adsorption experiment showed SN-GA has a maximum iodine adsorption capacity of 999 mg g-1 determined by Langmuir isotherm, and the adsorption process could be better described by the pseudo-second-order model.

Improved interfacial floatability of superhydrophobic and compressive S, N co-doped graphene aerogel by electrostatic spraying for highly efficient organic pollutants recovery from water

Sulfur and nitrogen co-doped graphene aerogel with Janus wettability of superhydrophobic/superhydrophilic was prepared with hydrothermal reduction combined with electrostatic spraying method. The upper surface exhibited an interconnected and porous 3D network with superhydrophobic property (water contact angle > 150°), while the under surface displayed a continuous membrane structure possessing rich wrinkles with superhydrophilicity (water contact angle < 5°). The hydrophobic mechanism was further demonstrated by FT-IR, XPS and theoretical calculations, resulting from the oxygen-containing functional groups decrease and the changes of surface electrostatic potentials and charge densities due to S, N co-doping into the graphitic network. More importantly, the Janus superwettability of the graphene aerogel enables it to stabilize at multiple interfaces, such as air/water, air/hexane, hexane/water and water/CCl4 interfaces, resolving the floating problem under windy conditions for the ultralight and hydrophobic materials, which is vital for the practical applications. The as-synthesized graphene aerogel also exhibits remarkable compressibility with full recovery even at 90% strain, and remains over 50% of maximum stress even after 1000 cycles at 90% strain. With high BET surface area (406.80 m2/g), high compressibility and robust structure, our graphene aerogel shows fast adsorption with high capacity and excellent recyclable performance, achieving up to about 65–192 times of its own weight for various oils and organic solvents.

Enhanced heterogeneous activation of peroxydisulfate by S, N co-doped graphene via controlling S, N functionalization for the catalytic decolorization of dyes in water

3D porous sulfur and nitrogen co-doped graphene aerogel has been fabricated by a facile one-pot process. Both experimental and theoretical studies have demonstrated that sulfur and nitrogen co-doping could synergistically enhance the catalytic performance for activating peroxydisulfate (PDS) compared to the original and N doped graphene aerogels. The ratio of sulfur/nitrogen in the aerogel can be controlled by regulating the additions of thiourea and urea sources, and the aerogel with the S/N ratio of about 1:2.5 shows a better catalytic effect due to more significant changes in the electrostatic potential and the surface charge distribution, as revealed by the theoretical simulations. The radical quenching tests indicated that both SO4·- and ·OH radicals could be formed in the SN-rGO aerogel + PDS system and contribute most to RhB degradation.

Boron and nitrogen co-doped graphene aerogels: Facile preparation, tunable doping contents and bifunctional oxygen electrocatalysis

Rational design of low-cost and highly-efficient bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is currently critical for renewable energy storage and conversion devices. Herein, we represent a series of three-dimensional porous B and N co-doped graphene aerogels (BN-GAs) using NH4B5O8 as precursor for B and N source by hydrothermal method and freeze-drying process. In this facile strategy, we can tune doping contents of B and N configurations in BN-GAs by simply changing the synthesis conditions. Linear sweep voltammetry results confirm that the increasing doping contents of pyridinic N and BC3 phases in BN-GAs can boost ORR activity, which may be because the enhanced synergy that arises from combining pyridinic N and BC3 phases can greatly improve ORR activity. The proposed BN-GAs not only show similar ORR activity to commercial Pt/C, but also more superior stability and excellent methanol tolerance than commercial Pt/C. Remarkably, the resultant BN-GAs also exhibit considerable OER activity and achieve desired performance as an air cathode for a rechargeable zinc-air battery device. Notably, this work may assist in a new insight to feasible preparation and molecular design of more advanced graphene-based catalyst, and can be extended to other catalytic system.