Three-dimensional Nitrogen-doped Graphene Research Articles

Electron-interactive 1D porous vertical NiCo2O4 nanowire and 3D N-doped graphene aerogel enable high hydroxyl-ion adsorption capacity for superior energy storage

Supercapacitors are a kind of highly efficient energy-storage device with long cycle life and high power density, however, their specific capacitance is insufficient for further application and development. In this work, a novel composite with one-dimensional (1D) NiCo2O4 nanowire arrays (NiCo2O4-NWA) vertically supported on three-dimensional (3D) nitrogen-doped graphene aerogel (NGA) is designed and facilely realized by hydrothermal reaction and thermal treatment. The NiCo2O4 nanowires, with length of ∼1 μm and diameter of ∼25 nm, display a porous structure and are regularly arranged on both sides of the sheets in nitrogen-doped graphene aerogel. The aerogel-supporting NiCo2O4 nanowires demonstrate a remarkably high specific capacitance of 2742 F g−1 at 1 A g−1, and an outstanding cyclic stability with capacitance retention of 90% even after 10,000 cycles at 80 A g−1. The density functional theory calculation shows the narrow band gap (0.32 eV) and strong electronic interaction and hydroxyl-ion adsorption effect of NiCo2O4 supported on NGA, resulting in superior specific capacitance and energy storage performance. The 3D nitrogen-doped graphene aerogel supporting 1D nanowire arrays represent a promising high-performance electrode material for application in the supercapacitors and other electrochemical energy-conversion and storage equipment.

Retraction: Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature.

Retraction of 'Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature' by Mojtaba Mahyari et al., Chem. Commun., 2014, 50, 7855-7857, https://doi.org/10.1039/C4CC01406E.

Retraction: Nickel nanoparticles immobilized on three-dimensional nitrogen-doped graphene as a superb catalyst for the generation of hydrogen from the hydrolysis of ammonia borane

Retraction of ‘Nickel nanoparticles immobilized on three-dimensional nitrogen-doped graphene as a superb catalyst for the generation of hydrogen from the hydrolysis of ammonia borane’ by Mojtaba Mahyari and Ahmad Shaabani, J. Mater. Chem. A, 2014, 2, 16652–16659, https://doi.org/10.1039/C4TA03940H.

Materials space-tectonics methodology of conductive mesoporous carbon nanohorns embedded graphene aerogels anchoring Pd nanocrystalline for an efficient ethanol oxidation reaction

Materials space-tectonics (MST) methodology is a powerful strategy to design catalytic materials synthesis to overcome the limitation of monotonous pore geometries and develop functional structures with surface-specific functions. Based on the MST, herein, carbon nanohorns (CNH) as “spacers” inserted into three-dimensional (3D) nitrogen-doped graphene aerogel (NG) anchoring Pd nanocrystalline (Pd/CNH@NG) was constructed through a facile hydrothermal approach and wet chemical reduction method without surfactant and employed as electrocatalyst for ethanol oxidation reaction (EOR). The introduction of CNH can provide important mesopore and macropore characters and generate more active sites to anchor Pd nanocrystalline on the basis of unique internal and interstitial nanopore structures, high surface area and conductive graphitic structure, then enhancing the electrocatalytic efficiency, stability and poison tolerance of catalysts. Meanwhile, the role of CNH doped NG also includes accelerating the reaction of the intermediate (CH3COads) manufactured on the Pd-based aerogels surface with adsorbed hydroxyl (OHads) due to coordination effect from Pyridinic-nitrogen and pyrrolic-nitrogen species. The electrochemical results reveal that the specific and mass activities of the obtained Pd/CNH@NG-2 aerogel (the mass ratio of graphene oxide and CNH is 1:3) are 1.38 and 2.86 times higher than those of the commercial Pd/C for EOR. Simultaneously, the current density of Pd/CNH@NG-2 still maintains 70 % after 500 cycles of complete CV, but commercial Pd/C only maintains 22.6 % of the initial activity. The synthesis of Pd/CNH@NG not only offers a porous three-dimensional aerogel for the EOR but also optimizes a facile strategy to fabricate superior supports for promoting the commercialization of DEFCs.

Boosting glycerol electrooxidation over palladium catalyst driven by boron-incorporation

The incorporating of metalloid elements into the interstices of Pd lattice is a powerful strategy to manipulate the binding strength of surface adsorbates and thereby to boost its electrocatalytic activity and anti-poisoning for many electrocatalytic reactions. In present work, a novel nanocomposite, the boron-incorporated palladium nanoparticles anchored on the three-dimensional nitrogen-doped graphene (PdBx/NG), was firstly fabricated through a simple hydrothermal synthesis followed by a facile wet chemical reduction method. Extensive physicochemical analyses were conducted to unveil the effects of the boron-incorporation on the properties of the as-synthesized electrocatalyst. More strikingly, the PdBx/NG displayed considerably boosted electrocatalytic behavior towards glycerol oxidation reaction (GOR), which largely outperformed the Pd/NG and benchmark Pd/C. The NG endowed PdBx/NG with three-dimensional architecture, rich pores and abundant nitrogen-containing functional groups. Furthermore, the boron-incorporation enabled the electronic effect (electronic modification) and strain effect (lattice expansion) for Pd. The superior contribution of NG and boron-incorporation enhanced electrocatalytic activity and reinforced stability of PdBx/NG for GOR. This study provides an alternative way for fabricating the boron-incorporated catalysts for electrochemical reactions and beyond.

Three-dimensional nitrogen-doped graphene quantum dots/reduced graphene oxide composite hydrogels as binder-free electrodes for symmetric supercapacitors

Herein, nitrogen-doped graphene quantum dots/reduced graphene oxide composite hydrogels (N-GQDs/rGOs) were prepared via a hydrothermal approach from graphene oxide (GO) aqueous solution. During the preparation of the samples, ammonia water was used as reducing agent, pH regulator and nitrogen dopant, and graphene quantum dots (GQDs) were used as spacer between graphene sheets. Benefiting from their three-dimensional porous structures, large specific surface area, large number of heteroatom functional groups (N, O) on the surface, and the synergistic effect between GQDs and graphene sheets, the synthesized samples exhibit excellent electrochemical performance. Particularly, the N-GQDs/rGO-20 sample based binder-free symmetric supercapacitor show a high specific capacitance of 277.8 F g−1 at 0.3 A g−1, and this value can still maintain at 220.9 F g−1 even at 10 A g−1 in 6 M KOH electrolyte. Moreover, the capacitance retention rate of the symmetric supercapacitor can reach 92.7% after 10,000 cycles at 10 A g−1, indicating its excellent cycle stability.

Enhancing electrocatalytic methanol oxidation of Pd-Ir nanoalloy through electron-rich catalytic interface induced by incorporating phosphorus

Incorporating less expensive nonmetal phosphorus (P) into noble metal-based catalysts has become a developing strategy to enhance the catalytic performance of electrocatalysts for methanol electrooxidation reaction (MOR), attributing to the electronic and synergistic structure alteration mechanism. In the work, three-dimensional nitrogen-doped graphene anchoring ternary Pd-Ir-P nanoalloy catalyst (Pd7IrPx/NG) was prepared by co-reduction strategy. As a multi-electron system, elemental P adjusts the outer electron structure of Pd and diminishes the particle size of nanocomposites, which heightens the electrocatalytic activity effectively and accelerate MOR kinetics in alkaline medium. The study reveals that the electron effect and ligand effect induced by P atoms on the hydrophilic and electron-rich surface of Pd7Ir/NG and Pd7IrPx/NG samples can reduce the initial oxidation potential and peak potential of COads, showing significantly enhanced the anti-poisoning ability compared with commercial Pd/C as the benchmark. Meanwhile, the stability of Pd7IrPx/NG is significantly higher than that of commercial Pd/C. The facile synthetic approach provides an economic option and a new vision for the development of electrocatalysts in MOR.

Heterogeneous activation of persulfate by macroscopic nitrogen-doped graphene oxide cubes for the degradation of antibiotic contaminants in water

As a sustainable and green approach, carbocatalysis, a metal-free strategy, has shown exceptional results in advanced oxidation processes (AOPs). Nonetheless, the recovery of these catalysts has been a major shortcoming over the years. Herein, three-dimensional nitrogen-doped graphene macrostructures (3D-NGMs), in the form of macro cubes, were synthesised by a simple cross-linking and thermal annealing procedure, after which they were employed in the activation of peroxydisulfate (PS) for the degradation of sulfamethoxazole (SMX). The catalytic cubes were loaded with different amounts of nitrogen precursor to investigate the role of nitrogen configuration in the sp2 hybridised carbon network on AOPs. NGC3 cubes with optimum N-loading exhibited outstanding performance for SMX degradation owing to their optimum N/C ratio. Various reaction parameters were studied to optimise the catalytic system. Comprehensive studies on the radical generation were done and illustrated the dominance of the non-radical pathway leading to the proposal of a possible reaction mechanism for SMX. This study not only suggests the role of nitrogen doping on graphene macrostructures but also provides novel insights into macro catalysis to overcome the recovery challenges posed by nano catalysis.

Boosting CO2 Electroreduction on Bismuth Nanoplates with a Three-Dimensional Nitrogen-Doped Graphene Aerogel Matrix

Electrochemical CO2 reduction reaction (CO2RR), which uses renewable electricity to produce high-value-added chemicals, offers an alternative clean path to the carbon cycle. However, bismuth-based catalysts show great potential for the conversion of CO2 and water to formate, but their overall efficiency is still hampered by the weak CO2 adsorption, low electrical conductivity, and slow mass transfer of CO2 molecules. Herein, we report that a rationally modulated nitrogen-doped graphene aerogel matrix (NGA) can significantly enhance the CO2RR performance of bismuth nanoplates (BiNPs) by both modulating the electronic structure of bismuth and regulating the interface for chemical reaction and mass transfer environments. In particular, the NGA prepared by reducing graphene oxide (GO) with hydrazine hydrate (denoted as NGAhdrz) exhibits significantly enhanced strong metal-support interaction (SMSI), increased specific surface area, strengthened CO2 adsorption, and modulated wettability. As a result, the Bi/NGAhdrz exhibits significantly boosted CO2RR properties, with a Faradaic efficiency (FE) of 96.4% at a current density of 51.4 mA cm-2 for formate evolution at a potential of -1.0 V versus reversible hydrogen electrode (vs RHE) in aqueous solution under ambient conditions.

A highly efficient electrocatalyst for oxygen reduction reaction: Spinel MnCo2O4 nanoparticles supported on three-dimensional Nitrogen-doped graphene material with interconnected hierarchical porous nanostructure

• MnCo 2 O 4 /3DNG catalyst was prepared by hydrothermal method using 3DNG as support. • 3DNG with hierarchical porous structure possessed enrich the defects and expose more active sites. • MnCo 2 O 4 /3DNG with hierarchical porous structure contributed to improve mass transfer. • MnCo 2 O 4 /3DNG demonstrated excellent ORR activity and higher durability than 20% Pt/C. We designed and synthesized spinel MnCo 2 O 4 nanoparticles supported on three-dimensional nitrogen-doped graphene (NG) with interconnected hierarchical porous nanostructure, in which polymer (2, 5-benzimidazole) (ABPBI) was used as the nitrogen precursor and the carbon precursor. Unique properties of ABPBI including nitrogen-rich aromaticity and rigid plane molecule were conductive to form NG structures through the pyrolysis dehydrogenative and carbonization. The as-prepared MnCo 2 O 4 -3DNG with interconnected hierarchical porous graphene structure possessed enriched defects and more exposed active sites, accelerating mass transport and facilitating diffusion kinetics for better catalytic ORR performance. MnCo 2 O 4 -3DNG exhibited a higher half-wave potential (0.85 V vs RHE) than 20 wt% Pt/C (0.83 V vs RHE). Moreover, the accelerated durability test and i-t chronoamperometry of MnCo 2 O 4 -3DNG revealed more excellent durability than 20 wt% Pt/C. The electrochemical tests results demonstrated that MnCo 2 O 4 -3DNG was promising as a cost-effective non-noble metal catalyst for ORR in fuel cell technology.

Pt3Ni alloy catalyst coupled with three-dimensional nitrogen-doped graphene for enhancing the alkaline hydrogen evolution

Developing high-performance Pt-based alloy catalysts with strong metal-support interaction is considered an effective strategy to optimise the intrinsic activity and stability of catalysts and has received extensive attention, but still challenging. Herein, Pt3Ni alloy nanoparticles coupled with three-dimensional N-doped graphene (Pt3Ni/3DNG) are prepared and used for enhancing the alkaline hydrogen evolution reaction (HER). It is found that the Pt3Ni/3DNG catalyst generates a tensile strain and give rise to a ligand effect on the surface of the active sites, which efficiently boost water dissociation and optimise H* desorption, thereby accelerating the alkaline HER kinetics. As a result, the Pt3Ni/3DNG catalyst exhibits an exceptional alkaline HER activity with a mass activity 14 times that of commercial 40 wt.% Pt/C at 70 mV and a high stability (no decay is observed after 10,000 cycles). This work demonstrates the function of quaternary-N and pyridinic-N in the HER, and provides a novel design for Pt-based alloy catalysts with high alkaline HER performance.

Oxygen vacancy defect tungsten-oxide-quantum-dot-modified nitrogen-doped graphene with interfacial tiny primitives to boost oxygen reduction reaction

Ultrafine quantum-dot-modified nitrogen-doped graphene has attracted board interest and has become frontier research in metal-air batteries and fuel cells. In this study, oxygen vacancy defect tungsten oxide quantum dots (V o -WO 3 QDs) are embedded in nitrogen-doped graphene (NG) to form abundant heterogeneous interfacial electrocatalysts (V o -WO 3 QDs/NG), which exhibits advanced electrocatalytic activity for oxygen reduction reaction (ORR) in an alkaline electrolyte. The optimized V o -WO 3 QDs/NG-5 (W content of 0.14 wt%) exhibits high onset potential (0.932 V vs. RHE) and decent half-wave potential (0.762 V vs. RHE) with high stability, which outperforms other reported tungsten metal oxide-based ORR electrocatalysts. The outstanding electrocatalytic performances of V o -WO 3 QDs/NG-5 are contributed by higher amount of oxygen vacancy and defects in V o -WO 3 QDs, as well as tunable interfacial electronic properties between the V o -WO 3 QDs and NG support. Furthermore, the density functional theory (DFT) is systematically conducted to determine the electronic properties and interface charge transmission for V o -WO 3 QDs/NG entity, providing important insight on the electrocatalysts in terms of band regulation and electron transport at the active interface between V o -WO 3 QDs and NG. Our finding paves an efficient pathway to design highly active hetero-structural and durable electrocatalysts for ORR applications based on defect-rich metal oxide QDs supported on nitrogen-doped graphene. Oxygen Vacancy Defect Tungsten oxide Quantum Dots Modified Three-dimensional Nitrogen-doped graphene with Interfacial Primitives Boosted Oxygen Reduction • Oxygen vacancy defect WO 3 quantum dots embedded N-doped Graphene enhanced ORR catalytic activity. • Interface electron transport are systematically simulated in heterojunctions using DFT system. • Vo-WO 3 QDs/NG-5 shows superior ORR catalytic activity and excellent cycle stability.

Three-dimensional nitrogen-doped graphene oxide beads for catalytic degradation of aqueous pollutants

Metal-free graphene-based catalysts have demonstrated excellent performance in advanced oxidation processes (AOPs). However, the recovery and reusability of these nanocatalysts are still a major issue. In this study, three dimensional (3D) nitrogen-doped reduced graphene oxide beads (NrGOb) were synthesized via a self-assembly method and then applied in heterogeneous activation of peroxymonosulfate (PMS) for the oxidation of hydroxybenzoic acid (HBA). The materials (NrGOb) were annealed at various temperatures ranging from 500 to 1000 °C, and the resulting NrGOb derived from 800 °C (NrGOb-800) exhibited the best performance for PMS activation. To avoid the challenging recovery, the degradation experiments were also performed in a packed-bed catalytic reactor. Various reaction parameters were investigated to optimize the efficiency of the system. Electron paramagnetic resonance (EPR) and quenching tests were carried out to differentiate the contribution of reactive radicals (SO4•-and•OH) in the degradation process and then aided in illustrating the degradation mechanism. Finally, the stability and reusability of the catalytic beads were investigated. The efficiency slightly declined with increased cycles; however, catalyst regeneration would be able to partially restore the active sites. The results suggest the feasibility of exploiting graphene-based macrostructures on the AOPs platform for the degradation of organic pollutants in commercial wastewater treatment plants.

Surface and interface engineering of MoNi alloy nanograins bound to Mo-doped NiO nanosheets on 3D graphene foam for high-efficiency water splitting catalysis

Designing high-efficiency and durable non-noble metal catalysts is essential for the large-scale application of electrocatalytic water splitting. Herein, MoNi alloy nanograins are embedded in Mo-doped NiO nanosheets by partial reduction treatment, which vertically grow on three-dimensional (3D) nitrogen-doped graphene foam substrate (MoNi@Mo-NiO@NGF). The hybrid composite demonstrates superb bifunctional electrocatalytic activity towards hydrogen/oxygen evolution reactions. Especially, it possesses the ultra-low hydrogen evolution overpotential of 56 mV at the current density of 10 mA cm−2 in alkaline condition. The excellent catalytic activity and remarkable stability can be attributed to the optimized surface electronic structure of MoNi alloy by Mo doping, the synergy interface interaction between MoNi nanograins and Mo-NiO substrate, and the high conductivity and corrosion resistance of NGF support. Thus, this work provides a new strategy for the high-performance catalyst towards overall water splitting by the dual regulation of surface and interface.

Uniformly distributed 1T/2H-MoS2 nanosheets integrated by melamine foam-templated 3D graphene aerogels as efficient polysulfides trappers and catalysts in lithium-sulfur batteries

• MF-GA-MoS 2 composite acts as a new separator-modified material. • 1T/2H-MoS 2 nanosheets were integrated onto the 3D graphene aerogel using melamine foam as template. • GA framework acts a conductive network and physical barrier of LiPSs. • 1T/2H-MoS 2 nanosheets can produce strong chemossorption to LiPSs and promote their conversion to Li 2 S 2 /Li 2 S. Lithium-sulfur (Li-S) batteries are regarded as one of the next-generation batteries because of their low cost and higher energy density than Li-ion batteries. However, the rapid capacity fading due to the shuttling effect of long-chain lithium polysulfides (LiPSs) between electrodes and sluggish redox kinetics remain a big hindrance in practical applications. Herein, three-dimensional nitrogen-doped graphene aerogel (GA) with uniformly distributed and defect-rich 1T/2H-MoS 2 nanosheets has been developed by adding melamine foam (MF) as the hard template. The resultant MF-GA-MoS 2 composites have strong electron transfer capabilities and rich catalytic activity sites that can adsorb and catalyze the conversion of LiPSs to Li 2 S 2 /Li 2 S, thus reducing the shuttle effect to improve the performance of Li-S batteries. Li-S batteries with the defect-rich MF-GA-MoS 2 composites modified separator exhibit amazing initial discharge capacity of 1323 mAh g −1 at 0.2C, high ratio capacity of 718 mAh g −1 at 1C after 400 cycles, and low decay rate of 0.0485% per lap after 800 cycles at 3C. This work provides a novel strategy for the development of separator modified materials with high adsorption and catalytic properties in Li-S batteries.

Hydrolysis of Organophosphorus Agents Catalyzed by Cobalt Nanoparticles Supported on Three-Dimensional Nitrogen-Doped Graphene.

Catalytic chemical degradations and many other methodologies have been explored for the removal and/or degradation of organophosphorus agents (OPs) that are often used as pesticides, nerve agents, and plasticizers. To explore more efficient and recyclable catalysts for the removal and/or degradation of OPs, we fabricate the composites of cobalt nanoparticles and three-dimensional nitrogen-doped graphene (Co/3DNG). We demonstrate that OPs can be hydrolyzed efficiently at ambient temperature by the Co/3DNG. Because of the unique structural and chemical properties of the supporting matrix 3DNG and active species Co-N, the catalytic activities of Co/3DNG composites are much higher than those of bare 3DNG, Co nanoparticles, or the Co nanoparticles physically mixed with 3DNG. We conclude that in the Co/3DNG composites, the interaction between 3DNG and Co stabilizes and distributes well the Co nanoparticles and affords the active catalytic species Co-N.

Polypyrrole-Wrapped SnS2 Vertical Nanosheet Arrays Grown on Three-Dimensional Nitrogen-Doped Porous Graphene for High-Performance Lithium and Sodium Storage

Polypyrrole-Wrapped SnS₂ Vertical Nanosheet Arrays Grown on Three-Dimensional Nitrogen-Doped Porous Graphene for High-Performance Lithium and Sodium Storage

Nitrogen and molybdenum co-doped CoP nanohoneycombs on 3D nitrogen-doped porous graphene as enhanced electrocatalyst for oxygen evolution reaction

The four-electron transfer process involved in anodic oxygen evolution reaction (OER) of electrocatalytic water splitting causes the sluggish kinetics and significantly limiting the efficiency of energy conversion. It's urgent to explore low-cost, efficient and stable electrocatalysts for OER. In the work, we design the nitrogen and molybdenum co-doped CoP with nanohoneycombs structure on three-dimensional (3D) nitrogen-doped porous graphene (N/Mo–CoP@NPG) as an efficient OER electrocatalyst. The N/Mo–CoP@NPG delivers the current density of 10 mA cm−2 at a low overpotential value of 201 mV in 1.0 M KOH, meanwhile the electrocatalytic activity shows no obvious degradation after 50 h. The NPG substrate provides plentiful ligaments for growth of N/Mo–CoP nanohoneycombs and 3D network for rapid electronic transfer. Additionally, doping N and Mo atoms into CoP synergistically modifies the micromorphology and electronic structure, benefiting the electrocatalytic ability. This work offers a promising strategy to improve the electrocatalytic activity of transition metal phosphides.

Hierarchical modulation of NiSe2 nanosheets/nanodendrites by phase engineering on N-doped 3D porous graphene as self-supporting anode for superior lithium ion batteries

In order to deal with the shortage of fossil fuel reserves and environmental pollution, lithium-ion batteries (LIBs) have been widely studied as a new type of sustainable green energy device. In the work, the NiSe2 nanosheets/nanodendrites hierarchical material with two phases is deposited on the framework of three-dimensional nitrogen-doped graphene (NPG) through the hydrothermal method to construct a self-supporting anode for LIBs. The NPG has ultralow self-weight as well as excellent electrical conductivity, which inhibits the agglomeration during the growth of active materials. Furthermore, the unique hierarchical NiSe2 active material also relieves its structural damage during the charge and discharge process. As a result, the NiSe2 combined with NPG (NiSe2@NPG) expresses specific capacities of 860 mAh/g and 568 mAh/g at current densities of 0.2 A/g and 3.2 A/g, respectively, making it a promising lithium-ion battery anode material.

N-Doped Carbon-Wrapped Cobalt–Manganese Oxide Nanosheets Loaded into a Three-Dimensional Graphene Nanonetwork as a Free-Standing Anode for Lithium-Ion Storage

A high-quality and centimeter-level three-dimensional (3D) nitrogen-doped graphene (NG) nanonetwork is synthesized via a chemical vapor deposition method to serve as a substrate and a current collector, which directly germinates active metal oxides to act as a free-standing electrode in lithium-ion batteries. By means of facile electrodeposition and annealing processes, the tetragonal spinel cobalt–manganese oxide nanosheets wrapped with polypyrrole pyrolytic carbon are in situ hybridized with a 3D NG nanonetwork. In particular, the introduced carbon protective layer can enhance the Li-ion storage capacity and cycle stability of the composite electrode. The metallic synergistic effect and rational carbonaceous hybridization jointly provide high-performance charge storage and cycle stability. Notably, the surface-controlled capacitive effect stands out contributing to the total charge storage more than ever in nanostructure electrodes.