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Among various clear energy generation processes, electrocatalytic water splitting or hydrogen evolution reaction (HER) has been considered as an efficient method for the sustainable production of hydrogen (H2) fuel. But, significant efforts are still required to develop cheap, effective and stable electrocatalysts for water splitting to achieve the economical production of H2. In the quest of finding cheap electrocatalysts, herein, we demonstrate the preparation of palladium (Pd) nanoparticles decorated nitrogen (N) doped highly reduced graphene oxide (NDG-Pd) based electrocatalysts. The nitrogen (N) doped highly reduced graphene oxide (NDG) was produced by using graphene oxide as precursor, which was reduced and doped with nitrogen, simultaneously in one-step hydrothermal method. Subsequently, Pd nanoparticles were decorated on the surface of NDG using a facile ultrasonic method to produce NDG-Pd. In order to restrict the amount of precious metal to reduce the cost of catalysts, very small percentage of Pd, such as, 1 and 3 % was utilized during the preparation of electrocatalysts. The as-prepared electrocatalysts were successfully characterized by using different methods such as, XRD, XPS, EDX, BET, SEM and TEM. Results confirmed the formation of slightly agglomerated, smaller size of Pd NPs on the surface of NDG with an average particle size of ∼ 6 nm. The as prepared nanocomposites NDG, NDG-Pd1% and NDG-Pd3% were used to prepare electrodes and their electrocatalytic activity was evaluated towards the production of H2 through water splitting. The results of electrochemical performance of as-prepared electrodes within the voltage range have revealed that among different samples prepared, the NDG did not show any current, whereas NDG-Pd3% showed a good potential for HER with current density ≈24 mA/cm2 at very low potential i.e. −0.2 V vs RHE.

Direct methanol fuel cells, in which electrocatalytic oxidation of methanol takes place, are one of the most promising technologies for facilitating the shift to renewable energy sources. However, they still suffer from high-catalyst-prices, as well as sluggish kinetics of methanol oxidation reaction (MOR). Therefore, herein, palladium/Nickel(II) hydroxide/nitrogen doped reduced graphene oxide (Pd/Ni(OH)2/N-rGO) hybrid was fabricated via facile two-step solution method and utilized as electrocatalyst for MOR. The in-situ electrochemical activation pre-treatment was proposed to engineer a highly active electrocatalyst. The Pd/Ni(OH)2/N-rGO, which had distinctive structural features along with robust synergistic effects, outperformed the commercial Pd electrocatalyst in terms of catalytic activity towards MOR, with elevated anodic peak current density values. The in-situ electrochemical activation pre-treatment lead to 3.3, 3.0, and 2.0-fold increase in activity of Pd/Ni(OH)2/N-rGO, Pd/N-rGO, and Pd/C, respectively. This research lays the door for a unique technique to manufacture high-performance, low-cost electrocatalysts that might be used in fuel cell technology instead of existing Pd electrocatalysts. • Pd/Ni(OH) 2 /N-rGO ternary hybrid was synthesized by two-step solution method. • In-situ electrochemical activation method was employed to boost the MOR activity. • The catalytic activity of Pd substantially promoted by incorporation of Ni(OH) 2 clusters. • Ni(OH) 2 assisted in the oxidative removal of intermediates carbonaceous poison. • N-rGO network would serve as a catalyst support material and stabilizer. [ABSTRACT FROM AUTHOR]

Ammonia electrooxidation reaction involving multistep electron-proton transfer is a significant reaction for fuel cells, hydrogen production and understanding nitrogen cycle. Platinum has been established as the best electrocatalyst for ammonia oxidation in aqueous alkaline media. In this study, Pt/nitrogen-doped graphene (NDG) and Pt/tungsten monocarbide (WC)/NDG are synthesized by a wet chemistry method and their ammonia oxidation activities are compared to commercial Pt/C. Pt/NDG exhibits a specific activity of 0.472 mA·cm−2, which is 44% higher than commercial Pt/C, thus establishing NDG as a more effective support than carbon black. Moreover, it is demonstrated that WC as a support also impacts the activity with further 30% increase in comparison to NDG. Surface modification with Ir resulted in the best electrocatalytic activity with Pt-Ir/WC/NDG having almost thrice the current density of commercial Pt/C. This work adds insights regarding the role of NDG and WC as efficient supports along with significant impact of Ir surface modification. [ABSTRACT FROM AUTHOR]

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. • N/Mo co-doped CoP was successfully constructed on 3D nitrogen-doped porous graphene. • Co-doping of N and Mo heteroatoms can optimize the morphology and surface structure of CoP. • N/Mo–CoP@NPG nanohoneycombs composite shows excellent activity and durability for oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

Among various clear energy generation processes, electrocatalytic water splitting or hydrogen evolution reaction (HER) has been considered as an efficient method for the sustainable production of hydrogen (H 2) fuel. But, significant efforts are still required to develop cheap, effective and stable electrocatalysts for water splitting to achieve the economical production of H 2. In the quest of finding cheap electrocatalysts, herein, we demonstrate the preparation of palladium (Pd) nanoparticles decorated nitrogen (N) doped highly reduced graphene oxide (NDG-Pd) based electrocatalysts. The nitrogen (N) doped highly reduced graphene oxide (NDG) was produced by using graphene oxide as precursor, which was reduced and doped with nitrogen, simultaneously in one-step hydrothermal method. Subsequently, Pd nanoparticles were decorated on the surface of NDG using a facile ultrasonic method to produce NDG-Pd. In order to restrict the amount of precious metal to reduce the cost of catalysts, very small percentage of Pd, such as, 1 and 3 % was utilized during the preparation of electrocatalysts. The as-prepared electrocatalysts were successfully characterized by using different methods such as, XRD, XPS, EDX, BET, SEM and TEM. Results confirmed the formation of slightly agglomerated, smaller size of Pd NPs on the surface of NDG with an average particle size of ∼ 6 nm. The as prepared nanocomposites NDG, NDG-Pd1% and NDG-Pd3% were used to prepare electrodes and their electrocatalytic activity was evaluated towards the production of H 2 through water splitting. The results of electrochemical performance of as-prepared electrodes within the voltage range have revealed that among different samples prepared, the NDG did not show any current, whereas NDG-Pd3% showed a good potential for HER with current density ≈24 mA/cm2 at very low potential i.e. −0.2 V vs RHE. [ABSTRACT FROM AUTHOR]

In the present work, NRGO and Ag/NRGO catalysts were synthesized using eco-friendly reducing agents. Graphene oxide was prepared as a substrate by electrochemical method. Then, using urea as nitrogen source, it was converted into graphene nitrogen dop under a temperature of 160 ° C and used as a silver bed. The presence of nitrogen in the graphene structure results in a better dispersion of the silver metal on graphene and prevents the accumulation of them. To investigate the catalytic behavior of electrocatalysts, linear scaling voltammetry test was used in alkaline medium for oxygen regeneration reaction. Ag / NRGO showed better catalytic behavior than the NRGO as the bare substrate. It also showed better kinetic behavior than NRGO.

A magnetic NG@CoFe2O4 photocatalyst was developed via a facile hydrothermal method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometry (VSM) techniques. The CoFe2O4 nanoparticles were found to have a size between 100-150 nm and were uniformly dispersed on the nitrogen doped graphene. Magnetic studies showed that the NG@CoFe2O4 photocatalyst can be easily separated from the solution by the simple bar magnet. The photocatalytic degradation of methylene blue dye (MB) was studied under visible irradiation. The photocatalytic performance of NG@CoFe2O4 photocatalyst was found to be influenced by structural and optical properties as well as the surface area of the samples. The NG@CoFe2O4 photocatalyst exhibited improved photodegradation performance when compared with pure CoFe2O4. The as synthesized NG@CoFe2O4 can be a probable candidate used as a visible-light active magnetically separable photocatalyst and so could be used as a potent separation tool in waste water treatment.

A facile one step solvothermal method is designed for the synthesis of visible light-sensitive ZnO-nitrogen doped graphene (ZNG) nano photocatalysts using ethylene glycol as a solvent as well as an agent to prevent aggregation of graphene layers. The deposition of ZnO nanoparticles onto the NG layers was confirmed by high resolution transmission electron microscope (HR-TEM), scanning electron microscope (SEM), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). UV–Vis spectroscopy (UV-Vis) was used to study the enhanced photocatalytic activity, which shows the red-shift of the band-edge as compared to ZnO nano particles. The enhancement in photocatalytic activity is possibly due to the synergistic effect of improved adsorptivity of dyes, enhanced visible light absorption and effective charge separation.

Ternary sulfur (S)-/silicon dioxide (SiO2)-/nitrogen-doped graphene (NG) composite has been prepared by simple heat treatment. Morphological study illustrates the well dispersion of sulfur in the layered structure of SiO2–NG. The initial specific capacity of S–SiO2–NG composite delivers 1204 mAh g−1, and it maintains the capacity of 716 mAh g−1 during the 100th cycle at 0.1 C rate with 96% of Coulombic efficiency. The enhanced cycling performance of S–SiO2–NG cathode is mainly attributed to the combined contribution from both SiO2 and NG. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of O2 via a two‐electron reaction pathway to H2O2 provides a possibility for replacing the current anthraquinone process, enabling sustainable and decentralized H2O2 production. Here, a nitrogen‐rich few‐layered graphene (N‐FLG) with a tunable nitrogen configuration is developed for electrochemical H2O2 generation. A positive correlation between the content of pyrrolic‐N and the H2O2 selectivity is experimentally observed. The critical role of pyrrolic‐N is elucidated by the variable intermediate adsorption profiles as well as the dependent negative shifts of the pyrrolic‐N peak on X‐ray adsorption near edge structure spectra. By virtue of the optimized N doping configuration and the unique porous structure, the as‐fabricated N‐FLG electrocatalyst exhibits high selectivity toward electrochemical H2O2 synthesis as well as superior long‐term stability. To achieve high‐value products on both the anode and cathode with optimized energy efficiency, a practical device coupling electrochemical H2O2 generation and furfural oxidation is assembled, simultaneously enabling a high yield rate of H2O2 at the cathode (9.66 mol h−1 gcat−1) and 2‐furoic acid at the anode (2.076 mol m−2 h−1) under a small cell voltage of 1.8 V. [ABSTRACT FROM AUTHOR]

The carbon dioxide reduction reaction (CO2RR) driven by renewable electricity is a promising way to tackle the CO2 emission woes and recycle use of CO2. The synthesis of electrocatalysts with high activity and selectivity for CO2RR to ethylene remains a great challenge. Herein, leaf‐like CuO nanosheets are fabricated in situ on nitrogen‐doped graphene (NG) by using a novel reduction‐oxidation‐reconstruction process. When used as a catalyst for the CO2RR in 0.1 M KHCO3, a high faradaic efficiency of approximately 30 % for ethylene with an ultra‐high ethylene/methane ratio of 190 was achieved at −1.3 V vs. the reversible hydrogen electrode. The SEM and TEM images confirm the leaf‐like CuO nanosheets display high‐curvature structures, while multiple distinguished grain boundaries constructed by CuO(110) and CuO(111) planes are verified by HRTEM. For the first time, we present a facile method to combine the high‐curvature structure and the grain boundary to enhance the selectivity of the CO2RR to ethylene over a CuO catalyst. [ABSTRACT FROM AUTHOR]

The aim of this study is to efficiently utilize catalytic properties of silver nanoparticles and nitrogen doped graphene and their combined synergistic effect. For this purpose, nitrogen doped reduced graphene oxide‐silver (NrGO‐Ag) nanocomposites were synthesized by a facile, environmentally friendly, one‐pot hydrothermal method for the first time and characterized by UV–Vis, FTIR, XRD, XPS, SEM, and TEM. Catalytic activity of the synthesized nanocomposites was tested against 4‐nitrophenol (4‐NP) and methylene blue (MB) reduction reactions in the presence of NaBH4. Total degradation was achieved in both reactions in 210 and 44 s, and pseudo first order reaction rate constants were calculated as 0.0071 and 0.0322 s−1 for 4‐NP and MB reduction reactions, respectively. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes (AOPs) counting heterogeneous photocatalysis has confirmed as one of the preeminent method for waste water remediation. In the present work, we have successfully fabricated novel visible-light-driven nitrogen-doped graphene (NG) supported magnetic ZnO/ZnFe 2 O 4 (ZnO/ZF/NG) and ZnO/CoFe 2 O 4 (ZnO/CF/NG) nanocomposites. ZnO synthesized via direct precipitation method. Hydrothermal method was used for the preparation of nitrogen-doped graphene supported magnetic ZnO/ZF (ZnO/ZnFe 2 O 4) and ZnO/CF (ZnO/CoFe 2 O 4) nanocomposites. The procured materials were scrutinized by assorted characterizations to acquire information on their chemical composition, crystalline structure and photosensitive properties. The absorption and photocatalytic performance of photocatalysts were studied via UV–Visible spectra. Photodegradation performance of the synthesized nanocomposites was estimated toward mineralization of methyl orange (MO) and malachite green (MG) dyes in aqueous solution. The high surface area of ZnO/ZF/NG and ZnO/CF/NG was suitable for adsorptive removal of MO and MG dyes. The photodegradation performance of heterojunction photocatalysts was superior to bare photocatalyst in 140 min under visible-light irradiation. Spectrophotometer, GC–MS (Gas chromatography–mass spectrometry) elucidation was carried out to expose the possible intermediates formed. Both ZnO/ZF/NG and ZnO/CF/NG were rapidly isolated from the aqueous phase by applying an external magnetic field in 20 sec and 2 min, respectively. The photocatalytic performance and stability of ZnO/ZF/NG and ZnO/CF/NG nanocomposites were confirmed by conducting 10 consecutive regeneration cycles. Owing to recyclability of ZnO/ZF/NG and ZnO/CF/NG, these heterogeneous nanocomposites might be used as cost-effective for treatment of discarded water. The observations endorse that the synthesized ternary heterogeneous nanocomposites facilitates wastewater decontamination using photocatalytic technology. [ABSTRACT FROM AUTHOR]

A layer-by-layer self-assembled nitrogen-doped graphene/PDDA/gold nanoparticle (NDG/PDDA/GNP) composite was described. Citrate-stabilizing gold nanoparticle colloids (GNPs) were electrostatically adsorbed onto NDG nanosheets using a cationic polyelectrolyte, polydiallyldimethylammonium (PDDA), as the linker, thereby creating a high-performance electrochemical interface. The morphology and chemical composition were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, infrared spectroscopy, and Raman spectroscopy. Analytical application was manifested by electrochemical sensing of uric acid (UA), a biomarker involved with a variety of clinical diseases. The prepared nanocomposite exhibited noticeable electroactivity to uric acid oxidation and can give effective peak separation with ascorbic acid and dopamine. Additionally, the nanocomposite practically averted from other potentially interferents including glucose, urea, and serotonin, thus allowing selective voltammetric detection of UA in the biological matrix. Under the optimal condition, peak currents measured by differential pulse voltammetry were proportional to UA concentrations in the range of 0.5~100 μM (R2 = 0.998), with the detection limit of 53 nM. The NDG/PDDA/GNP nanocomposite as presented herein holds potential for aiding the diagnosis of UA-associated diseases and should be a new opportunity for biochemical analysis and biosensing applications. [ABSTRACT FROM AUTHOR]

Catalytic efficacy of metal-based catalysts can be significantly enhanced by doping graphene or its derivatives in the catalytic protocol. In continuation of previous work regarding the catalytic properties of highly-reduced graphene oxide (HRG), graphene-oxide (GO) doped mixed metal oxide-based nanocomposites, herein we report a simple, straightforward and solventless mechanochemical preparation of N-doped graphene (NDG)/mixed metal oxide-based nanocomposites of ZnO–MnCO3 (i.e., ZnO–MnCO3/(X%-NDG)), wherein N-doped graphene (NDG) is employed as a dopant. The nanocomposites were prepared by physical milling of separately fabricated NDG and ZnO–MnCO3 calcined at 300 °C through eco-friendly ball mill procedure. The as-obtained samples were characterized via X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Raman, Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX) and surface area analysis techniques. To explore the effectiveness of the obtained materials, liquid-phase dehydrogenation of benzyl alcohol (BOH) to benzaldehyde (BH) was chosen as a benchmark reaction using eco-friendly oxidant (O2) without adding any harmful surfactants or additives. During the systematic investigation of reaction, it was revealed that the ZnO–MnCO3/NDG catalyst exhibited very distinct specific-activity (80 mmol/h.g) with a 100% BOH conversion and 3). Under the optimum catalytic conditions, the catalyst successfully transformed various aromatic, heterocyclic, allylic, primary, secondary and aliphatic alcohols to their respective ketones and aldehydes with high selectively and convertibility without over-oxidation to acids. In addition, the ZnO–MnCO3/NDG was also recycled up to six times with no apparent loss in its efficacy.

The novel sponge-like N-doped reduced graphene oxide films (N-rGO) were synthesized successfully via a facile one-step route at 800 °C. The as-prepared films are few-layer and have loose sponge-like structure between layers and the N-doping content can reach to 7.11% and C/O is 17:1. As an anode material of Li-ion battery (LiBs), the as-prepared N-rGO flim exhibit excellent electrochemical properties. It delivers an initial discharge capacity of 1673 mAh g−1 and the reversible specific discharge capacity of 906 mAh g−1 at the current density of 100 mA g−1. Even at the current density of 1.6 A g−1, the reversible specific capacity still could remain at 346 mAh g−1 after 500 cycles. The appearance of N-doping microstructure of rGO with a high content and loose sponge-like framework might be applied to explain thus enhanced electrochemical properties. The typical FESEM image of N-rGO (a) and long cycling performance of Sample I(b) at a current density of 1.6 A g−1for 500 cycles. Unlabelled Image • The N-rGO films were successfully synthesized via a facile one-step solid state reaction route. • The as-prepared N-rGO films have high N content and loose sponge-like microstructure. • Temperature can greatly affect the doping process, especially the film thickness and the pore structures formation. • The as-prepared N-rGO films exhibit good electrochemical performance and cycle stability at different current densities. [ABSTRACT FROM AUTHOR]

• N-doped defective graphene (N)G has three types of N atoms, including pyridinic ones. • CO 2 and NH 3 adsorption on (N)G reveals the presence of acid and basic sites. • (N)G promotes Michael addition of methylene active compounds to unsaturated ketone. • (N)G promotes the Henry addition of nitromethane to benzaldehyde. • DFT calculations indicates that the most basic sites are pyridinic N atoms at the edge. N-doped defective graphene [(N)G] obtained by pyrolysis at 900 °C of chitosan contains about 3.7% of residual N atoms, distributed as pyridinic, pyrrolic and graphitic N atoms. It has been found that (N)G acts as basic catalyst promoting two classical C C bond forming nucleophilic additions in organic chemistry, such as the Michael and the Henry additions. Computational calculations at DFT level of models corresponding to the various N atoms leads to the conclusion that N atoms are more stable at the periphery of the graphene sheets and that H adsorption on these sites is a suitable descriptor to correlate with the catalytic activity of the various sites. According to these calculations the most active sites are pyridinic N atoms at zig-zag edges of the sheets. In addition, N as dopant changes the reactivity of the neighbour C atoms. Water was found a suitable solvent to achieve high conversions in both reactions. In this solvent the initial distribution of N atoms is affected due to the easy protonation of the N Py to N PyH sites. As an effect, C edge sites adjacent at N PyH with an appropriate reactivity towards the α-C-H bond breaking are formed. The present results show the general activity of N-doped graphene as base catalysts and illustrate the potential of carbocatalysis to promote reactions of general interest in organic synthesis. [ABSTRACT FROM AUTHOR]

Green and sustainable metal-free heterogeneous photocatalyst and their structures are an essential role for the environmental remediation and clean energy production, but the construction of meal-free, highly active and low-cost photocatalyst has remained a great challenge. This paper deals with a simple and novel metal-free nitrogen-doped graphene covalently grafted with graphitic carbon nitride (NG@g-C 3 N 4) nanocomposite was synthesized by an ultra-sonication method. The as-prepared nanocomposite was characterized by UV–vis diffuse reflection spectroscopy, FT-IR, XRD, TEM, BET surface areas, photoluminescence and electrochemical impedance spectroscopy. Notably, the NG@g-C 3 N 4 is exhibits efficient degradation of methyl orange and the efficiency was achieved by nearly 100% within 35 min. These remarkably observed photocatalytic activities can be attributed to the well adsorption capability of visible light, high surface area and great charge separations are due to the synergistic effect of NG grafted to g-C 3 N 4. Meanwhile, the photocatalytic mechanism is also studied and investigated. It is hoped that our work can provide a robust way to create metal-free photocatalysts for water remediation and beyond. A simple and novel metal-free nitrogen-doped graphene covalently grafted with g-C 3 N 4 nanocomposite was synthesized and it was exhibits highly robust photo degradation towards methyl orange. Image 10249 • Synthesis of a novel metal-free NG grafted g-C 3 N 4 nanocomposite via an ultra-sonication method. • Metal-free NG@g-C 3 N 4 exhibits remarkably enhanced photocatalytic activity. • The NG@g-C 3 N 4 has good stability and reusability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hierarchical hybrid of exfoliated MoS 2 assembled N-doped GR was facilely prepared. • The hybrid demonstrated highly catalytic activity for HER in alkaline medium. • The hybrid required small overpotential of 208 mV to obtain a current of 10 mA cm−2. • The hybrid shows better stability for a long-term operation than commercial Pt/C. Abstract A novel hierarchical heterostructure of molybdenum dichalcogenide nanosheets homogeneously assembled on nitrogen doped graphene layer (MoS 2 NSs/N-doped GR) was successfully developed by an easy and cost-effective strategy. The MoS 2 NSs/N-doped GR was then utilized for accelerating hydrogen evolution reaction (HER) in alkaline medium. It was found that the nanohybrid exhibited highly efficient catalytic activity towards HER with higher current density and smaller overpotential as compared to those of other synthesized materials. In this context, the nanohybrid required an overpotential of only 208 mV to achieve a current density of 10 mA cm−2, along with a small Tafel slope of 79 mV dec-1, which is close to those of a commercial Pt/C. An outstanding stability of the nanohybrid for long-term operation was also demonstrated. The obtained results suggest that the MoS 2 NSs/N-doped GR nanohybrid can be a potential candidate for HER in overall water splitting application. [ABSTRACT FROM AUTHOR]

Abstract Gd and Sn co-doped BiFeO 3 nanoparticles were synthesized by sol-gel route and Bi 0.95 Gd 0.05 Fe 0.95 Sn 0.05 O 3 /Nitrogen doped graphene nanohybrid (BGFSO/NG, where NG: 1%, 2%, 3%, 4%, 5%, 6%) were synthesized by sprinkling BGFSO nanoparticles and NG into ethanol solution followed by thermal drying. Structural and morphological properties of BiFeO 3 (BFO) nanoparticles, BGFSO nanoparticles, NG and BGFSO/NG, were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallite size BGFSO nanoparticle is about 20 nm. The photocatalytic activities of the as-prepared BiFeO 3 (BFO) nanoparticles, BGFSO, NG and BGFSO/NG nanohybrid were measured by the degradation of methyl orange (MO) under simulated sunlight irradiation. BGFSO/N-G nanohybrid shows enhanced photocatalytic activity. The improved photocatalytic activity is attributed to the effective transfer of photogenerated electrons from nanoparticles NG nanosheets, consequently leads to an increased availability of h + for the photocatalytic reaction. Additionally, hydroxyl (⋅OH) radicals were detected by the photoluminescence method through terephthalic acid (TPA) as a probe molecule and are found to be generated on the irradiated BGFSO and BGFSO/NG. Highlights • Gd and Sn co-doped BiFeO 3 /nitrogen doped graphene nanocomposite was synthesized by using sol gel method. • Enhanced photocatalytic properties were observed for Gd and Sn co-doped BiFeO 3 /nitrogen doped graphene nanocomposites. [ABSTRACT FROM AUTHOR]

Methanol crossover is one of the major problems which reduces the performance of direct methanol fuel cells (DMFCs). Utilization of methanol tolerant cathode electrocatalysts with comparable activity, lower cost, and higher durability than those of current Pt-based electrocatalysts is an essential step towards commercialization of DMFCs. In this research, for the first time the performance of hydrothermally produced nitrogen-doped reduced graphene oxide (NRGO) with nitrogen content of 4.6 wt% was compared with that of commercial 20 wt% Pt/C as cathode electrocatalysts of passive DMFC. The polarization curves of cells with various methanol concentrations (1.5, 3.0, and 4.5 M) were recorded. The results suggested the cell with NRGO cathode could operate at higher optimum methanol concentration in contrast to the cell with Pt/C cathode. The results showed that at the same methanol concentration the maximum power density, the fuel efficiency, and the current stability for the cell with NRGO cathode are higher than those of Pt/C cathode about 208%, 269%, and 77%, respectively. Higher temperature of cathode current collector of the cell with Pt/C cathode, in spite of its lower power output, presented an evidence of oxidation of permeated methanol on its cathode surface. Also, EIS measurements clarified that CO ads oxidation reaction, an intermediate of methanol oxidation reaction (MOR), on cathode side of cell with Pt/C cathode implies a relatively huge impedance on the overall cell operation. By contrast, in the case of cell with NRGO cathode due to its inertness towards MOR, the overall cell impedance significantly reduced. [ABSTRACT FROM AUTHOR]

Abstract The fabrication of efficient and durable novel electrocatalysts using a facile and cheap way is a potential approach for real energy conversion technology. In this research, a novel nanohybrid based on iron nickel nanoparticles well attached on nitrogen doped graphene nanosheets (Fe 2 Ni 1 NPs/N-Gr) was synthesized through a simple refluxing strategy followed by a calcination process. It was discovered that the material displayed good catalytic behavior for oxygen reduction reaction (ORR) in alkaline environment. The ORR kinetics of the material primarily occurred through a 4-electron transferred pathway consistent with high diffusion limit current density, excellent onset potential (−0.013 V) as well as half-wave potential (−0.065 V). Furthermore, the material showed good stability and outstanding methanol tolerance as compared to a commercial Pt/C catalyst. The resulting catalytic performance of the material was assumed to the synergistic effect from bimetallic Fe 2 Ni 1 NPs and thin nitrogen doped graphene, which improved electroactive site numbers, promoted charge transfer ability, and adjusted adsorption energy for oxygen molecules. The results imply that such novel materials may be an effective and low-cost catalyst for ORR in energy conversion technology. Graphical abstract Image 1 Highlights • Fe 2 Ni 1 nanoparticles anchored nitrogen doped graphene is facilely synthesized. • The hybrid produces good catalytic performance towards ORR, relative to Pt/C. • Fe 2 Ni 1 nanoparticles and nitrogen sites on graphene simultaneously enhance ORR. • The hybrid exhibits superior durability and methanol tolerance than Pt/C. [ABSTRACT FROM AUTHOR]

Abstract Electrochemical methanol reformation (ECMR) method has been identified as one of the most effective method for on-site hydrogen production. However, concentrated research towards the development of efficient inexpensive hydrogen evolution reaction (HER) electrocatalyst holds the pivotal role in realizing the hydrogen economy. In this context, for the first time N-graphene supported Pd (Pd/NG) was synthesised and employed as an HER catalyst in ECMR process. N-graphene was synthesised by modified Hummer's method followed by Pd deposition through hydrothermal route. The electrocatalytic activity of Pd/NG for hydrogen evolution was evaluated by CV and LSV techniques. Tafel slope of Pd/NG and Pt/C was calculated from LSV curves and was found to be 33 and 31 mV/decade, respectively. Exchange current density was found to be 3.6 and 3.2 × 10−4 A cm−2 for Pd and Pt catalysts, respectively. The enhanced electrocatalytic activity is majorly attributed to the N-doping and uniform distribution of Pd nano particles on graphene. Further, the performance of Pd/NG was also evaluated in single ECMR cell using Pt–Ru/C at anode and Pd/NG at cathode as electrocatalysts. The results indicated the suitability of Pd/NG as cathode electrocatalyst for HER in ECMR process. Graphical abstract Image 1 Highlights • Synthesis of nitrogen doped graphene supported Pd electrocatalyst (Pd/NG). • Physico-chemical and electrochemical characterization of Pd/NG electrocatalyst. • Hydrogen evolution reaction with lower onset potential, less Tafel slope and high exchange current density. • Performance evaluation of Pd/NG as hydrogen evolution catalyst in electrochemical methanol reformation. [ABSTRACT FROM AUTHOR]

Abstract Novel hierarchically porous titanium-metal organic frameworks/nitrogen-doped graphene (Ti-MOFs/NG) nanocomposite derived from titanium-metal organic frameworks (Ti-MOFs) and the nitrogen-doped graphene (NG) has been originally synthesized successfully. Notably, the Ti-MOFs/NG nanocomposite has been for the first time investigated in detail, as oxygen reduction reaction (ORR) catalyst of cathodic materials for fuel cells. The results show that the Ti-MOFs/NG nanocomposite possesses excellent ORR performances, whether in alkaline or acidic medium, due to existences of the Ti 3 N 2-x , C 2 O 7 Ti 2.3 , H 2 Ti 5 O 11 , Ti and TiO active ORR segments. Specifically, the onset potential (E 0) and the Tafel slope value of the Ti-MOFs/NG nanocomposite are 1.14 V and 17.84 mV dec−1 in 0.1 M HClO 4 , respectively. Similarly, high ORR efficiency of the Ti-MOFs/NG nanocomposite also exhibit in alkaline medium. The relative current density can still keep 99.88% of the original value after 10800 s measurements in 0.1 M KOH. Additionally, small electrochemical impedance and excellent tolerance toward fuel molecules have been exhibited in both electrolytes. These ORR properties are superior to those of most of previously reported materials derived from other MOFs, in both alkaline and acidic media. Thus, the Ti-MOFs/NG nanocomposite is as a novel promising candidate for ORR catalyst to solve the main problems of sluggish reaction kinetics of the ORR, high cost of precious metal catalysts and low durability of the traditional catalysts, applied to fuel cells, metal-air batteries and further to water splitting in energy conversion and storage devices. [ABSTRACT FROM AUTHOR]

Abstract Constructing junctions between semiconductors is an effective way to promote charge separation and thus to improve the photoelectrochemical (PEC) performances, and specifically, p-n heterojunction is considered as a very promising structure. Herein, we designed and fabricated MoS 2 /nitrogen doped graphene hydrogels (MoS 2 /NGH) p-n heterojunction by a facile one-pot hydrothermal route. The as-fabricaterd MoS 2 /NGH heterostructures demonstrated the excellent PEC activity, exhibiting enhanced photocurrent intensity by the fast transfer and separation rate of photogenerated electron-hole owing to the construction of p-n heterojunction. Based on the high PEC performances of the MoS 2 /NGH heterostructure, a novel sensitive PEC sensor was developed for the determination of chloramphenicol (CAP) with the assistance of aptamer. In the presence of target molecules, the as-fabricated PEC sensor could recognize the CAP quickly and then consume the holes in the interface of heterostructures, inhibiting the recombination of photogenerated electron-hole pairs, resulting the enhanced photocurrent. Specially, with the concentration of CAP increased, the photocurrent enhanced gradually. Excellent linearity was obtained in the concentration range from 32.3 ng/L to 96.9 μg/L, and the limit of detection was 3.23 ng/L. Moreover, the as-fabricated PEC sensor exhibited rapid response, high stability, low-cost and high selectivity, which could be successfully applied to the analysis of CAP in honeycomb samples. Highlights • MoS 2 /NGH p-n heterojunctions were prepared by the one-pot hydrothermal route. • Such p-n heterojunction were beneficial to facilitate the charge transfer. • A simple and novel PEC aptasensor for CAP assay was developed based on MoS 2 /NGH. • This sensor exhibited high sensitivity, low detection limit, wide linear range, and etc. • The sensor was successfully applied to the analysis of CAP in honeycomb. [ABSTRACT FROM AUTHOR]

Abstract In this work, carbon quantum dots (CQD) encapsulated in super small platinum nanocrystals core-shell architecture/nitrogen doped graphene hybrid nanocomposite (CQD@PDA@PtNCs-NGR) was design synthesized. Without using any capping reagent, stabilizer and surfactant, very small CQD was served as template and anchoring point for the synthesis of Pt NCs with a super small size (2.25 nm) and a uniform distribution. Meanwhile, dopamine (DA) was used as bridging agent, positioning agent and weak reducing agent to make Pt2+ grow on the CQD. Combine the high dispersed Pt NCs with high specific surface area and high conductivity of NGR, the CQD@PDA@PtNCs-NGR shows excellent electrocatalytic performance towards the biosensing of DNA damage biomarker- 8-Hydroxy-2′-deoxyguanosine (8-OH-dG). A very low detection limit of 0.45 nM and 0.85 nM (S/N = 3), a wide linear range of 0.013 μM–109.78 μM and a high sensitivity of 7.912 μA μM−1cm−2 and 4.190 μA μM−1cm−2 were obtained. The fabricated CQD@PDA@PtNCs-NGR realized the detection of 8-OH-dG in human urine practical sample. Furthermore, CQD@PDA@PtNCs-NGR was applied for the determination of 8-OH-dG generated from damaged DNA and damaged guanine (G), respectively. This work effectively combines the electrochemical signal of 8-OH-dG with DNA damage, confirms the mechanism of DNA damage, which might pave a new way to establish the associations between degree of DNA damage and 8-OH-dG. Graphical abstract Image 1 Highlights • CQD encapsulated in super small PtNCs/NGR hybrid nanocomposites. • Without using any capping reagent, stabilizer and surfactant. • CQD served as template and anchoring point. • High electrochemical biosensing performance for DNA damage biomarker. • Realize detection of 8-OH-dG from damaged DNA and urine sample detection. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ni 3 V 2 O 8 and Fe 2 VO 4 NPs anchored NG synthesized by simple and cost-effective hydrothermal technique. • Ni 3 V 2 O 8 /NG and Fe 2 VO 4 /NG hybrids are employed as supercapacitor electrodes. • Both electrodes show ultra-high specific capacitance with excellent rate capability and superior cycling stability. • The ASC achieves a high energy density of ∼77.2 W h kg−1 at 863 W kg−1 and an ultra-long cycle life. Abstract Solid-state supercapacitors (SCs) are well-known as one of the most competitive power sources for modern electronics. However, most of the reported solid-state SCs suffer from low specific capacitance and energy density. Herein, a novel strategy for the synthesis of nickel vanadium oxide (Ni 3 V 2 O 8) and iron vanadium oxide (Fe 2 VO 4) nanoparticles (NPs) anchored nitrogen doped graphene (NG) for high energy solid-state asymmetric SC (ACS) through a simple and cost-effective hydrothermal technique was demonstrated. SEM and TEM analysis reveals that active Ni 3 V 2 O 8 and Fe 2 VO 4 NPs with uniform size are anchored on NG sheets. Electrochemical performance of Ni 3 V 2 O 8 /NG and Fe 2 VO 4 /NG electrodes showed that both have ultra-high specific capacitances (∼1898 F g−1 and 590 F g−1 at current density of 1 A g−1, respectively), tremendous rate capabilities, and superior cycling stabilities. Most significantly, solid-state ASC consisting of Ni 3 V 2 O 8 /NG as a cathode and Fe 2 VO 4 /NG as an anode which achieves a high energy density of ∼77.2 W h kg−1 at a power density of 863 W kg−1 and an ultra-long cycle life (capacitance retention of ∼83.3% after 20,000 cycles). This study emphasizes the development of a wide variety of energy storage systems for modern electronics. [ABSTRACT FROM AUTHOR]

Cobalt-nitride (Co 4 N) nanoparticle-decorated nitrogen-doped graphene sheets were obtained via the nitrogen doping of a graphene-oxide precursor and simultaneous nitride formation. The non-precious metal catalyst formed in this one-step synthesis exhibits high electrocatalytic oxygen reduction activity and hence provides a promising alternative to conventional Pt/C alkaline fuel cell cathode catalysts. The reported composites were formed from the mixture of lyophilized graphene-oxide nanosheets and cobalt(II) acetate in ammonia atmosphere at 600 °C. The average Co 4 N particle size increased from 14 to 201 nm with the increase in cobalt content. The oxygen reduction activity of the new catalysts was comparable to that of non-noble metal systems described in the literature, and also to the widely-used carbon black supported platinum catalysts. The highest reduction current density under alkaline conditions was found to be as high as 4.1 mA cm −2 with the corresponding electron transfer number of 3.6. Moreover, the new system outperformed platinum-based composites in terms of methanol tolerance, thus eliminating one of the major drawbacks (besides high price and limited availability), of noble metal catalysts. [ABSTRACT FROM AUTHOR]

Graphene based materials with excellent physical properties have attracted much attention in the field of energetic materials. Notably, heteroatom doping could modify the property of graphene. Herein, nitrogen‐doped graphene (NGO) with a tunable hierarchical morphology and high surface areas was prepared by a hydrothermal method. NGO composites with 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20) were obtained by recrystallization in ethyl acetate. Subsequently, the catalytic activities of NGO and undoped reduced graphene oxide (rGO) on the thermal decomposition of CL‐20 were investigated using differential scanning calorimetry (DSC). The decomposition temperature, self‐accelerating decomposition temperature, and thermal ignition temperature of CL‐20 all decrease under the influence of NGO. This is attributed to change in charge distribution of carbon atoms influenced by nitrogen dopants and more active sites induced on graphene surface. As a result, NGO exhibits enhanced catalytic effect on the thermal decomposition of CL‐20. [ABSTRACT FROM AUTHOR]

Abstract Oxygen reduction reaction (ORR) is a key component of numerous energy conversion equipment, including metal-air batteries and fuel cells. Reasonably designing high-efficiency non-noble materials as ORR electrocatalysts is crucial for large-scale practical applications. In this work, a calcination-hydrothermal method is used to prepare Co 3 O 4 @g-C 3 N 4 (g-C 3 N 4 wrapped Co 3 O 4 nanoparticle) supported on nitrogen doped graphene (NG). The electrochemical activity of composites is estimated by cyclic voltammograms and linear sweep voltammetry in 0.1 M KOH medium. Owing to the positive synergistic role stemming from the Co 3 O 4, g-C 3 N 4 , Co-N x effective sites and N modified graphene in the composite material, the Co 3 O 4 @g-C 3 N 4 /NG owns positive onset potential of 0.920 V (vs. RHE) and half-wave potential of 0.846 V (vs. RHE), which are superior to onset potential of 0.917 V and half-wave potential of 0.824 V for commercial Pt/C, respectively. Additionally, it also exhibits longer-term stability and stronger methanol resistance comparing with Pt/C. The nonprecious metal catalyst could be used as a hopeful catalyst to substitute commercial Pt/C for ORR. Graphical abstract Image 1 Highlights • NG supported Co 3 O 4 @g-C 3 N 4 was successfully prepared by a hydrothermal strategy. • ORR performance of Co 3 O 4 @g-C 3 N 4 /NG is superior to commercial Pt/C. • The current of Co 3 O 4 @g-C 3 N 4 /NG still retains 97.6% after 12 000 s reaction. • Co 3 O 4 @g-C 3 N 4 /NG exhibits stronger methanol resistance comparing with Pt/C. [ABSTRACT FROM AUTHOR]

A metal-free highly torn amine functionalized nitrogen doped graphene (HT-AFNG) used as hydrogen evolution reaction (HER) catalyst is prepared by using a simple synthesis method involving the hydrothermal reaction of graphene oxide in the presence of ammonia and the subsequent ball milling. The metal-free HT-AFNG is efficient for the HER in the acid solution and can deliver an onset potential of 100 mV and an overpotential of 350 mV at the current density of 10 mA cm −2 , which is much lower than those of the singly and dually doped graphene reported previously. The amine functionalized and nitrogen doped structure plays an important role in the high catalytic activity of the HT-AFNG, where the amine group can greatly reduce the |ΔG H* | value at both defect and edge sites as well as increases the electron transfer capability of nitrogen dope graphene (NG). Significantly, the highly torn structure also makes a big contribution on the high catalytic activity of the HT-AFNG, since it allows for the good accessibility of the active sites for the HER. The strategy involves the introduction of electron donating groups open a new research pathway towards the improvement of HER catalytic activity of graphene-based materials. [ABSTRACT FROM AUTHOR]

A new flower-like hybrid structure consisting of nitrogen-doped 3-dimensional (3D) graphene and vertically aligned graphene has been synthesized using a combination of low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques. Active nitrogen (N) species were found to be essential for the growth of the flower-like morphology. N-doping was responsible for enhanced electrical conductivity and wettability of the obtained nano-carbon hybrid structure. Based on the conducted studies a growth mechanism has been proposed. The high specific surface area, low resistance to charge transfer and enhanced specific capacitance of this nitrogen-doped hybrid structure, makes it an excellent candidate material for supercapacitors.

Development of highly functional and durable catalysts in a cost-effective way is a promising approach for practical energy conversion applications. In this study, a novel catalyst, cobalt iron carbide nanoparticles encapsulated by nitrogen doped graphene nanosheets, is successfully synthesized through a simple refluxing strategy followed by a post annealing process. It is found that the catalyst exhibits excellent catalytic activity for oxygen reduction reaction in alkaline medium. The oxygen reduction reaction kinetics of the catalyst mainly follow a 4-electron transferred pathway along with good diffusion limit current density, highly positive onset potential (−0.04 V) and half-wave potential (−0.11 V). In addition to catalytic activity, the catalyst demonstrates advanced superior stability, and excellent methanol tolerance in comparison with commercial platinum catalyst. The impressive catalytic performance of the catalyst is attributed to the unique mesoporous metal-core/graphene-shell architecture in which high interactions between two transition metals and transition metal-carbon synergistically provide enhanced catalytically active sites, accelerate interfacial charge transfer, and optimize oxygen adsorption energy. The results demonstrate that such catalyst can be an alternative low-cost and efficient catalyst for oxygen reduction reaction in energy conversion applications. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen-doped highly fluorescent graphene quantum dots (N-GQDs) were synthesized, using ammonia as nitrogen and d -glucose as carbon source, using a facile microwave-assisted protocol, where the N/C ratio could be varied from 0.19 to 0.25 (% w/w, determined from EDAX). The as-synthesized quantum dots consisting of one to three graphene monolayers exhibited high crystalline morphology with an average size of 1.8 ± 0.2 nm. HRTEM data showed the presence of both pyridinic-N and pyrrolic-N structures. Semiconductor profile of the N-GQDs was extensively probed, and it was noticed that the optical bandgap, knee-voltage and break-down voltage varied linearly with the N/C ratio. The doped samples showed with an optical bandgap ≈5.3 eV at the maximum nitrogen doping yielding n-type semiconductor property. Clear Zener diode attributes with a large forward bias current (100–200 mA), and a smaller reverse bias current of typically half that value was found. Highlights • Nitrogen-doped highly fluorescent graphene quantum dots (N-GQDs) were synthesized using a facile microwave-assisted protocol, where the N/C ratio could be varied from 0.19 to 0.25 (% w/w). • The as-synthesized quantum dots consisting of one to three graphene monolayers exhibited high crystalline morphology with an average size of 1.8 ± 0.2 nm. • Semiconductor profile of the N-GQDs was extensively probed, and it was noticed that the optical band gap, knee-voltage and break-down voltage varied linearly with the N/C ratio. • Clear Zener diode attributes with a large forward bias current (100–200 mA). • A smaller reverse bias current of typically half that value was found. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor based on nitrogen doped graphene (NGE) and palygorskite (Pal) for the simultaneous detection of hydroquinone (HQ) and catechol (CT) has been proposed. Pal is particularly pointed out for its appreciable specific surface area and reactive-OH groups on its surface. Acid treatment Pal demonstrated better physico-chemical properties, which are propitious to electrochemical sensor construction. The introduction of NGE not only improved the poor conductivity of Pal but also served as an excellent adherent matrix. The modified electrode demonstrated the enhanced redox peak currents of HQ and CT with good discrimination. Under optimized conditions, the linear ranges for HQ and CT were 2–50 μM and 1–50 μM, with detection limit (LOD) of 0.8 μM and 0.13 μM, respectively. The result designates that the Pal/NGE composite promises to be a new eco-friendly modified material for sensor fabrication. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene-ZnS composite (NG-ZnS) was synthesized by thermal treatment of graphene-ZnS composite (G-ZnS) in NH 3 medium. In the second step, the as-synthesized samples were deposited on indium tin oxide glass (ITO) by electrophoretic deposition for photocatalytic hydrogen evolution reaction. The as-prepared NG-ZnS-modified ITO electrode displayed excellent photocatalytic activity, rapid transient photocurrent response, superior stability and high recyclability compared to the pure ZnS and G-ZnS-modified ITO electrode due to the synergy between the photocatalytic activity of ZnS nanorods and the large surface area and high conductivity of N-graphene. [ABSTRACT FROM AUTHOR]

A facile one step solvothermal method is designed for the synthesis of visible light-sensitive ZnO-nitrogen doped graphene (ZNG) nano photocatalysts using ethylene glycol as a solvent as well as an agent to prevent aggregation of graphene layers. The deposition of ZnO nanoparticles onto the NG layers was confirmed by high resolution transmission electron microscope (HR-TEM), scanning electron microscope (SEM), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). UV-Vis spectroscopy (UV-Vis) was used to study the enhanced photocatalytic activity, which shows the red-shift of the band-edge as compared to ZnO nano particles. The enhancement in photocatalytic activity is possibly due to the synergistic effect of improved adsorptivity of dyes, enhanced visible light absorption and effective charge separation. [ABSTRACT FROM AUTHOR]

Atomically dispersed metals and their environments strongly influence their electrocatalytic activities. In this work, we synthesized a series of cobalt/nitrogen doped graphene (Co-NG) catalysts. Cobalt atom dispersion and aggregation on NG's basal plane, bond states of cobalt and nitrogen along with graphene basal plane defect and their impacts on hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities and kinetics were intensively studied. We found that a geometrically controlled formation of active Co N and Co C sites in the NG's basal plane is the key issue for improving interfacial Faradic reaction kinetics and thus enhancing hydrogen evolution. Differently, chemical bonding of finely dispersed cobalt atoms with oxygen, nitrogen and carbon together improves interfacial water oxidation kinetics for achieving high OER activity. [ABSTRACT FROM AUTHOR]

FeMoO 4 nanorods and their rare earth (Eu 3+ and Tb 3+ ) doped composites with nitrogen doped graphene (NG) were synthesized by facile hydrothermal method in aqueous medium. X-ray diffraction (XRD) analysis of the as-synthesized samples was done to study the phase purity and crystalline nature. FTIR and Raman Spectroscopy have been studied for investigating the bonding in nanostructures. The surface morphology of the samples was investigated with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The photolumniscent nature of the samples was investigated by the using the fluorescence spectrophotometer. The photocatalytic degradation efficiency of the prepared pure FeMoO 4 and its rare earth doped composites with nitrogen doped graphene was evaluated as function of visible light irradiation versus concentration of methylene blue (MB dye). The prepared nanocomposites show enhanced photocatalytic efficiency as compared to the bare FeMoO 4 nanorods. [ABSTRACT FROM AUTHOR]

We present an in-situ polyol assisted synthesis approach for the preparation of silver nanowires (AgNW) over the nitrogen doped graphene (NG) sheets and has been tested as a viable LIBs anode material for the first time. The use of NG serves as nucleation sites, thereby facilitating the growth of AgNWs. The specific material design of the as-prepared NG-AgNW hybrids involves some advantages, including a continuous AgNW-graphene conducting network. Since AgNWs are electrically conductive, it provides an electrical contact with NG sheets which can effectively help the charge transport process and limit the variations in volume during the lithiation/de-lithiation processes. Apart from this, the insertion of metallic Ag nanowires into a percolated NG network increases the interlayer distance of NG sheets and prevent its restacking. Moreover, the more porous nature of the hybrid structure accommodating the large volume changes of AgNWs. As an anode material for LIBs, the NG-AgNW hybrid displays a remarkable initial discharge capacity of 1215 mAh g −1 and attains a stable capacity of 724 mAh g −1 at a current density of 100 mA g −1 after 50 cycles. The electrode exhibits a stable reversible capacity of 714, 634, 550 and 464 mA h g −1 at 0.1, 0.2, 0.5, 1 Ag −1 respectively. The reversible capacity (710 mAh g −1 ) at 0.1 Ag −1 is recovered after the cycling at various current densities confirming outstanding rate performance of the material. In addition, the coulombic efficiency, the NG-AgNW anode retains nearly 99% after the second cycle, further indicating its excellent reversibility. The hybrid material exhibits better cycling stability, greater rate capability, capacity retention and superior reversible capacity than that of bare AgNW and NG sheets. Our smart design will pave way for the development of efficient electrode materials for high capacity and long cycle life LIBs. [ABSTRACT FROM AUTHOR]

This paper describes a highly sensitive and selective electrochemical sensing of catechol (CC) using gold nanoparticles decorated nitrogen doped graphene covalently grafted polypyrrole (Au@NG-PPy) nanocomposite modified electrode. The Au@NG-PPy nanocomposite was synthesized by in-situ oxidative polymerization method and characterized by various techniques such as FT-IR, XRD, Raman, SEM, HR-TEM, EDX and mapping analysis. Under the optimized condition, the Au@NG-PPy nanocomposite modified electrode shows a higher electrocatalytic activity towards oxidation of catechol compared to NG and NG-PPy. The enhanced electrochemical activity of the catalyst is owing to better electron transfer efficiency, good conductivity and high surface area of the nanocomposite. A very good selectivity is able to be achieved by as-synthesized Au@NG-PPy toward the determination of 0.1 μM CC in the presence of 100-fold higher concentrations of common interferents including hydroquinone. The catechol sensor exhibits a wide sensing linear range from 0.1–0.9 μM and the detection limit is found to be 0.0016 μM (S/N = 3). The proposed method has been successfully applied for the selective determination of CC in various real samples such as apple juice, green tea and tap water with good recoveries. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene (N-G) catalyst emerges as one of the promising non-platinum group metal (non-PGM) catalysts with the advantages of low cost, high oxygen reduction reaction (ORR) activity, stability, and selectivity to replace expensive PGM catalysts in electrochemical systems. In this research, nanoscale high energy wet (NHEW) ball milling is first investigated for the synthesis of N-G catalysts to make conventional problems such as sintering or localized overheating issues negligible. The successful synthesis of N-G catalysts with comparable catalytic performance to 10 wt% Pt/C by using this method has been published. This paper focuses on understanding the effect of grinding speed and grinding time on the particle size and chemical state of N-G catalysts through the physical and chemical characterization. The research result shows that (1) the final particle size, nitrogen doping percentage, and nitrogen bonding composition of synthesized N-G catalysts are predictable and controllable by adjusting the grinding time, the grinding speed, and other relative experimental parameters; (2) the final particle size of N-G catalysts could be estimated from the derived relation between the cracking energy density and the particle size of ground material in the NHEW ball milling process with specified experimental parameters; and (3) the chemical composition of N-G catalysts synthesized by NHEW ball milling is controllable by adjusting the grinding time and grinding speed. [ABSTRACT FROM AUTHOR]