Co-doped Reduced Graphene Oxide Research Articles

Selective NO2 Gas Sensors Employing Nitrogen- and Boron-Doped and Codoped Reduced Graphene Oxide.

In this paper, we develop high-performance gas sensors based on heteroatom-doped and -codoped graphene oxide as a sensing material for the detection of NO2 at trace levels. Graphene oxide (GO) was doped with nitrogen and boron by a chemical method using urea and boric acid as precursors. The prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained results proved the successful reduction of graphene oxide by doping effects, leading to the removal of some oxygen functional groups and restoration of an sp2 carbon structure. New bonds in honeycombs, such as pyridinic, pyrrolic, graphitic, B-C3, B-C2-O, and B-O, were created. Compared to the nondoped GO, the N/B-rGO materials exhibited enhanced responses toward low concentrations of NO2 (<1 ppm) at 100 °C. Particularly, the N-rGO-based device showed the highest sensitivity and lowest limit of detection.

Nitrogen, sulfur coordinated metal complex and reduced graphene oxide hybrid materials as counter electrodes for application in dye-sensitized solar cells

Graphene, as one of the carbon-based materials, is considered to be a potential replacement for platinum and has been widely used as a counter electrode in dye-sensitized solar cells to achieve low-cost and high electrocatalytic materials. In this work, we synthesized a nitrogen-sulfur-coordinated iron complex as a source of heteroatoms, and prepared iron-nitrogen-sulfur co-doped reduced graphene oxide (FeNS-rGO) composite material by mixing with different mass ratios of graphene oxide (GO) and thermal annealing under nitrogen at 400 °C. The sintered GO was transformed into rGO, which increased the conductivity of materials, while the doping of nitrogen and sulfur atoms enhanced the carrier mobility and conductivity of the material. The distribution of Fe on graphene also improved the catalytic performance of material. FeNS-rGO (5:1), used as the CE in DSSC, showed superior reduction catalytic activity for I−/I3− compared to platinum and demonstrated an excellent power conversion efficiency of 8.17 %, which outperformed platinum. This proves that the graphene composite material doped with iron, nitrogen, and sulfur has excellent performance and can be used as a substitute for platinum.

Nitrogen and sulfur co-doped reduced graphene oxide (rGO)/gold nanoparticles hybrids for SERS sensing platform

Nitrogen and sulfur co-doped reduced graphene oxide (rGO)/gold nanoparticles hybrids for SERS sensing platform

Comparative study on the structural and electrochemical properties of nitrogen-doped and nitrogen and sulfur co-doped reduced graphene oxide electrode prepared by hydrothermal technique

Nitrogen- and co-nitrogen- and sulfur-doped reduced graphene oxide (named N-rGO and N/S-rGO) was prepared by a simple hydrothermal technique using urea and thiourea as doping agents, respectively, to improve the properties of supercapacitor electrodes. Both were compared with rGO in electrochemical evaluations. The supercapacitor using N-rGO in 1 M H2SO4 provided the largest specific capacitance, 99 F g−1, while those using N/S-rGO and rGO exhibited 51 and 19 F g−1 at 0.25 A g−1, respectively. Furthermore, the supercapacitors using N-rGO and N/S-rGO electrodes showed a smaller charge transfer resistance (Rct) and a lower IR-drop than those using the rGO electrode, indicating a faster charge transfer at the interface between electrode and electrolyte and higher electronic conductivity due to N or N/S heteroatom doping in the graphene oxide structure. Furthermore, the N-rGO electrode has a higher sp2 hybridization ratio and a lower ID/IG ratio than the N/S-rGO electrode. Furthermore, the lowest contact angles of the N/S-rGO electrode were found, which was attributed to better aqueous electrolyte compatibility than the N-rGO and rGO electrodes. Therefore, the higher electrical conductivity of the N-rGO electrode reveals more relevant characteristics for high-performance supercapacitors than the good wettability of the N/S-rGO electrode.

Analysis of the Performance of Phosphorus and Sulphur Co-Doped Reduced Graphene Oxide as Catalyst in Vanadium Redox Flow Battery

In a vanadium redox flow battery, the traditional polyacrylonitrile based graphite felt (GF) electrode suffers the problems of low electrochemical catalytic activity and low specific surface area. To improve the performance of the GF electrode, we prepared phosphorus and sulphur co-doped reduced graphene oxide (PS-rGO) as catalyst with the simple treatment of reduced graphene oxide (rGO) in the mixture of phytic acid and sulfuric acid. The GF electrode modified with PS-rGO (PS-rGO-GF) was characterized by scanning electron microscope, specific surface area, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge tests. The PS-rGO-GF shows enhanced performance toward VO2+/VO2 + redox reaction. The battery with the PS-rGO decorated GF presents an excellent battery performance with the energy efficiency of 81.37% at the current density of 80 mA cm−2 and the corresponding discharge capacity of 772 mAh due to the high catalytic activity of PS-rGO.

Comparative Study on the Structural and Electrochemical Properties of Nitrogen Doped and Nitrogen and Sulfur Co-Doped Reduced Graphene Oxide Electrode Prepared by Hydrothermal Technique

Comparative Study on the Structural and Electrochemical Properties of Nitrogen Doped and Nitrogen and Sulfur Co-Doped Reduced Graphene Oxide Electrode Prepared by Hydrothermal Technique

Synthesis of nitrogen and sulfur co-doped reduced graphene oxide by hydrothermal method for fabrication of cathodes in dye-sensitized solar cells

Carbon-based materials have been known as non-metal electrocatalysts with both high performance and low cost for the reduction at the cathode of dye-sensitized solar cells (DSSCs). In this work, nitrogen and sulfur co-doped reduced graphene oxide (NSG) materials were synthesized via using graphene oxide (GO) as a precursor with reducing agent thiourea as the source of providing heteroatoms. Furthermore, NSG materials were extensively prepared via hydrothermal treatment with the investigation of different mass ratios of GO to thiourea. To study the impact of the quantity of reductant on the properties of NSG, reduced graphene oxide (rGO) was prepared by reducing GO with ascorbic acid as a reference sample. Moreover, NSG and rGO cathodes were both prepared by drop-casting method, while platinum (Pt) cathodes were fabricated using commercial Pt paste by screen-printing method. The DSSCs based on NSG cathodes with ratio of GO to thiourea of 1:10 exhibited an efficiency of 7.21 %, which was similar to commercial DSSCs Pt (7.44 %), proving that the judicious heteroatom doping of GO might introduce a potential candidate for increasing performance of DSSCs.

Ultrafine CuS anchored on nitrogen and sulfur Co-doped graphene for selective CO2 electroreduction to formate

Electrochemical conversion of CO2 into hydrocarbons can effectively alleviate the energy crisis and promote carbon cycle. Herein, we report that small-size CuS nanoparticles are confined in nitrogen and sulfur co-doped reduced graphene oxide (CuS/N,S-rGO) for electrochemically reducing CO2 to formate. Specifically, the CuS/N,S-rGO electrode achieves maximum Faradaic efficiency of 82% for formate formation at −0.63 V versus the reversible hydrogen electrode (RHE). Moreover, this catalyst exhibits a stable performance during 20 h-electrolysis. Experiments demonstrate that the doping of nitrogen and sulfur can create an abundance of active sites on the graphene nanosheets to accelerate the CO2 reduction reaction (CO2RR). The CuS/N,S-rGO electrode exhibits excellent performance for CO2RR is attributed to the synergistic effect between N,S-rGO and CuS, and graphene can improve stability of composite. This work provides an efficient electrocatalyst for CO2RR and offers a facile and environmental friendly approach to synthesize small-size Cu-based composites.

A simple electrochemical sensor for quercetin detection based on cadmium telluride nanoparticle incorporated on boron, sulfur co-doped reduced graphene oxide composite

Quercetin (QR) is an essential component of the human diet, according to that low-cost, rapid, and portable sensors are required for the detection of QR in the diet supplements, fruits, vegetables, and pharmaceutical samples. A highly sensitive, low-cost, and facile hydrothermally synthesized cadmium telluride (CdTe) with (BS-RGO) boron- sulphur co-doped reduced graphene oxide nanocomposite based electrochemical sensor material for the detection of (QR) was established successfully. Here, prepared the CdTe/BS-RGO nanocomposite was confirmed by the morphological and structural examination such as FESEM, HRTEM, EDX, XRD, Raman, and XPS techniques. The electrical conductivity of the electrode material investigated by EIS and CV analysis, which confirmed the electrical conductivity of CdTe was boosted by the BS-RGO nanosheets. The electrochemical studies were established that the developed CdTe/BS-RGO sensor was highly selective and sensitive to QR. Furthermore, the CdTe/BS-RGO sensor exhibits good sensitivity, an excellent low detection limit (LOD) and a wide linear range was 2.3492 μA μM−1 cm−2, 18 nM, and 0.001–564 µM respectively for QR detection under optimized experimental conditions. In addition, we investigated the realistic performance of the proposed sensor for QR detection in grape juice and apple juice samples.

Ivermectin detection using Ag@ B, S co-doped reduced graphene oxide nanohybrid

Silver nanoparticles (AgNPs) modified boron and sulfur co-doped reduced graphene oxide (B, S@rGO) were prepared by one-pot hydrothermal method for the first time. The combination between AgNPs and B, S@rGO decreases stacking of B, S@rGO and decreases the particle size of AgNPs; in addition, it enhances the effective surface area and electro-catalytic activities of the nanocomposite. The morphology and structure of AgNPs/B, S@rGO were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron microscope (XPS), Raman spectroscopy, UV-Vis spectroscopy, thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET). The electro-catalytic activity of AgNPs/B, S@rGO was studied using cyclic voltammetry (CV), electron impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Because of the synergetic effects of AgNPs and B, S@rGO, the modified electrode displayed considerably enhanced sensitivity to ivermectin (IVM) determination. The voltammetric response is linear over the range of 0.3–60.0 nM with LOD (S/N = 3) of 0.1 nM. The proposed sensor exhibited good selectivity, reproducibility, and long-term stability. The modified electrode was used to analyze IVM in injections, urine, and tap-water with recoveries % of 99.6–105.8% and RSDs of 2.14–3.65%.

Nitrogen and sulfur co-doped reduced graphene oxide-gold nanoparticle composites for electrochemical sensing of rutin

The extraordinary biological and physiological properties of rutin have been used in the preparation of therapeutical drugs. So it is very significant to develop a simple and sensitive method for rutin determaination in pharmaceutical samples. Herein, nitrogen and sulfur co-doped reduced graphene oxide attached with gold nanoparticles (NS-rGO/AuNPs) was developed for electrochemical determination of rutin. The NS-rGO was first prepared by a simple one-step thermal annealing method, and AuNPs were embedded onto NS-rGO through the interaction force of Au with N and S atoms. Detailed characterizations showed that the AuNPs are well dispersed and the presence of nitrogen and sulfur are significant. The NS-rGO/AuNPs modified electrode exhibited a significantly enhanced electrocatalytic activity towards rutin compared with NS-rGO, N-rGO and S-rGO modified electrodes. The excellent performance was achieved by the synergistic effect of AuNPs and heteroatoms co-doping. As a consequence, the NS-rGO/AuNPs based sensor showed a wide linear range of 0.2–1400 nM with a nanomolar detection limit of 0.067 nM (S/N = 3). Also the sensor exhibited satisfying selectivity, reproducibility, and stability. Finally, the sensor was successfully used to determine rutin in pharmaceutical tablets.

High performance supercapacitors based on samarium molybdate/nitrogen and phosphorous co-doped reduced graphene oxide electrodes

Nanocomposites produced with samarium(III) molybdate/N, P co-doped reduced graphene oxide (Sm2MoO6/NPRGO) combination may be very useful in the field of supercapacitors due to the active interaction between these two components. In this study, we used the sonochemical method, which is quite simple and cheap, to produce Sm2MoO6/NPRGO nanocomposite, which draws attention with its high-quality electrochemical performance. Surface and structural properties of Sm2MoO6 nanoparticles, NPRGO and Sm2MoO6/NPRGO nanocomposite structures were studied by X-ray photoemission spectroscopy (XPS), nitrogen adsorption/desorption studies, scanning electron microscopy, and X-ray diffraction analysis. The symmetric supercapacitive performance of the Sm2MoO6/NPRGO electrode exhibits a specific capacitance of 689 F g−1 (at 2 mV s−1) and could maintain 99.9% capacity after 4000 charge–discharge cycles. Additionally, the symmetric supercapacitors based on nanocomposite electrode demonstrate a high energy density (23.2 W h kg−1 at 250 W kg−1), outstanding power density (8000 W kg−1 at 14.4 W h kg−1). Generally, this nanocomposite was synthesized for the first time and its supercapacitive properties were investigated. The nanocomposite electrode exhibited good supercapacitor response, remarkable rate performance and excellent cycling stability in both 0.5 M Na2SO4 electrolyte.

Alpha-MnO2 nanofibers/nitrogen and sulfur-co-doped reduced graphene oxide for 4.5 V quasi-solid state supercapacitors using ionic liquid-based polymer electrolyte

α-MnO2 nanofibers combined with nitrogen and sulfur co-doped reduced graphene oxide (α-MnO2/N&S-rGO) were prepared through simple hydrothermal and ball milling processes. Structural characterization results by X-ray diffraction, X-ray photoemission spectroscopy, electron microscopy and Raman spectroscopy demonstrated that α-MnO2 nanofibers with the average diameter of ~40 nm were well dispersed on N&S-rGO nanoflakes. The synthesized material was incorporated into supercapacitor (SC) electrodes and assembled with the quasi-solid-state electrolyte comprising N,N-Diethyl-N-methyl-N-(2-methoxy-ethyl)ammonium bis (trifluoromethyl-sulfonyl)amide [DEME][TFSA]/polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP) to produce coin-cell SCs. Electrochemical performances of SCs were measured by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. From the electrochemical data, SC using α-MnO2/N&S-rGO exhibited a good specific capacitance of 165F g−1 at 0.25 A g−1 with a wide potential window of 0–4.5 V, corresponding to a high energy density of 110 Wh kg−1 and a power density of 550 W kg−1. In addition, it exhibited good electrochemical stability with a capacitance retention of 75% after 10,000 cycles at 1 A g−1 and a low self-discharge loss. The attained energy-storage performances indicated that the α-MnO2/N&S-rGO composite could be highly promising for high-performance ionic liquid-based quasi solid-state supercapacitors.

Nitrogen, Sulfur Co-Doped Reduced Graphene Oxide: Synthesis and Characterization

Objective and Method: In this present research, a simple hydrothermal implantation technique for synthesizing N,S co-doped reduced graphene oxide (NS-r-GO) has been presented in which thiourea was used as a single-source precursor of N and S atoms. Results: Maximum N and S atoms, with an atomic percentage of 3.50 and 7.50 (at.%), were achieved in the GO matrix at the reaction temperature of 250°C. Introduction of N and S atoms into the GO lattice was confirmed by X-ray photoelectron spectroscopy (XPS). Different chemical bonds such as –C– S–C, C=O, N–O, and C–N–C have been suggested from the corresponding C1s, N1s, O1s, and S2p high-resolution XPS spectral analyses. Conclusion: FT-IR measurement also confirmed the presence of different functional groups as well as the formation of different bonds such as –OH, –N–H, –C=O, –C–OH, and C-S. XRD and Raman spectroscopy analyses confirmed the defects structures that arose from the penetration of N and S atoms into the GO lattice.

Methyl Parathion Detection Using SnS2/N, S–Co-Doped Reduced Graphene Oxide Nanocomposite

The rapid and ultralow detection of toxic organophosphate chemicals is a well-known, important step to reduce adverse health issues and yet also remains challenging. Here, we show electrochemical d...

Enhanced Hydrogen Storage Properties of MgH2 Using a Ni and TiO2 Co-Doped Reduced Graphene Oxide Nanocomposite as a Catalyst.

To improve the hydrogen storage properties of Mg/MgH2, a Ni and TiO2 co-doped reduced graphene oxide [(Ni-TiO2)@rGO] nanocomposite is synthesized by a facile impregnation method and introduced into Mg via ball milling. The results demonstrated that the dispersive distribution of Ni and TiO2 with a particle size of 20–200 nm in the reduced graphene oxide matrix led to superior catalytic effects on the hydrogen storage properties of Mg-(Ni-TiO2)@rGO. The initial hydrogenation/dehydrogenation temperature for Mg-(Ni-TiO2)@rGO decreased to 323/479 K, 75/84 K lower than that of the additive-free sample. The hydrogen desorption capacity of the Mg-(Ni-TiO2)@rGO composite released 1.47 wt.% within 120 min at 498 K. When the temperature was increased to 523 K, the hydrogen desorption capacity increased to 4.30 wt.% within 30 min. A hydrogenation/dehydrogenation apparent activation energy of 47.0/99.3 kJ·mol−1 was obtained for the Mg-(Ni-TiO2)@rGO composite. The improvement in hydrogenation and dehydrogenation for the Mg-(Ni-TiO2)@rGO composite was due to the reduction of the apparent activation energy by the catalytic action of (Ni-TiO2)@rGO.

Hexagonal-WO3 nanorods encapsulated in nitrogen and sulfur co-doped reduced graphene oxide as a high-performance anode material for lithium ion batteries

Nanocomposites consisting of hexagonal WO3 nanorods embedded into nitrogen, sulfur co-doped reduced graphene oxide nanosheets (h-WO3/NSG) have been synthesized through a combination of ultrasonic processing and hydrothermal reactions. The nanocomposite containing 54 ​wt% of (N, S)-doped reduced graphene oxide shows an excellent discharge capacity of 1030 mAh g-1 at the first cycle and high rate capacities ranging from 513 to 150 mAh g-1 at the current density ranging from 100 to 2000 ​mA ​g-1, respectively. In addition, the synthesized WO3/NSG nanocomposite also exhibits remarkable cycle stability with a high discharge capacity of 196 mAh g-1 at the current density of 1500 ​mA ​g-1 for 200 cycles. The excellent electrochemical performance of h-WO3/NSG nanocomposite can be attributed to synergistic contributions from (1) the small size of WO3 nanorods, which increases the contact surface area with the electrolyte, effectively shortening the diffusion length of Li+ ions leading to high Li+ incorporation within h-WO3; (2) the structural support provided by the NSG matrix, which alleviates the large volume change of WO3 nanorods during Li+ insertion/extraction; and (3) the large numbers of surface defects provided by nitrogen and sulfur co-dopants, which serve as channels to improve the Li+ diffusion. Furthermore, electrochemical impedance spectroscopy (EIS) measurement demonstrates that nitrogen, sulfur co-doped reduced graphene oxide can reduce the electrochemical impedance of the electrode, further improving the electrochemical performance of the anode. This study provides important strategies for the design of future high performance anode materials for lithium ion battery.

Zeolitic-imidazolate-framework-derived Co@Co3O4 embedded into iron, nitrogen, sulfur Co-doped reduced graphene oxide as efficient electrocatalysts for overall water splitting and zinc-air batteries

Rational design and fabrication of nonprecious metallic multifunctional catalysts with superior performance are crucial for energy-related electrochemical devices. Herein, we report the synthesis and electrochemical properties of a sandwich-like Co@Co3O4 embedded into Fe, N, S co-doped reduced graphene oxide (Co@Co3O4/FeNS-RGO) nanocomposite catalyst. The designed Co@Co3O4/FeNS-RGO catalyst is synthesized by pyrolysis of one-pot solvothermal method-induced nano-zeolitic imidazolate framework (ZIF)/graphene oxide nanocomposite using dimethylsulfoxide as both the solvent and sulfur source. The synthesized catalyst exhibits the outstanding electrocatalytic activity in basic media for oxygen reduction reaction and oxygen evolution reactions, which outperforms the commercial Pt/C and IrO2 catalysts, respectively. In addition, the synthesized catalyst also shows a promising electrocatalytic activity towards hydrogen evolution reaction. The performance of the thus-assembled zinc-battery and the overall water-splitting device reveals that the synthesized Co@Co3O4/FeNS-RGO can be practically applied in energy-related electrochemical devices with great activity and stability.

Synthesis of nitrogen/sulfur co-doped reduced graphene oxide aerogels for high-performance supercapacitors with ionic liquid electrolyte

Graphene with a unique two-dimensional lamellar structure is considered an attractive carbon-based electrode material for supercapacitors. However, the actual electrochemical performance of graphene-based supercapacitors is far below the theoretical level. In this work, reduced graphene oxide aerogels co-doped with different amounts of nitrogen and sulfur (N/S-rGAs) were prepared via a one-pot hydrothermal approach using trithiocyanuric acid as a doping agent. Characterization of the materials showed that the optimal N/S-rGA had a high sulfur content (4.1 at%) and an interconnected porous network structure that provided accessible diffusion channels for electrolyte ions, thus leading to low ion diffusion resistance. The optimal N/S-rGA displayed high electrical conductivity of 11.5 S cm−1 and a specific capacitance of 180.5 F g−1 at 1 A g−1. This N/S-rGA delivered a high energy density of 75 Wh kg−1 at a power density of 0.9 kW kg−1 in an ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF4) electrolyte, and its energy density was still 33 Wh kg−1 when its power density was 15 kW kg−1. Consequently, N/S-rGAs are promising electrode material for high-performance ionic liquid-based supercapacitors.

An electrochemical sandwich immunosensor for cardiac troponin I by using nitrogen/sulfur co-doped graphene oxide modified with Au@Ag nanocubes as amplifiers.

A voltammetric sandwich immunoassay is described for the biomarker cardiac troponin I (cTnI). The gold nanocube-functionalized graphene oxide (AuNC/GO) is employed as a substrate to accelerate the electron transfer and to immobilize more primary antibodies. It also employs composite materials prepared from bimetallic gold/silver core-shell nanocubes and nitrogen and sulfur co-doped reduced graphene oxide as the signal amplifier. The introduction of N and S into GO enlarges the active surface and accelerates the electron transfer rate. Such unique characteristics render the material an effective support substrate to load more Au@AgNC and to immobilize an increasing number of second antibodies via Ag-N bonds. After specific binding with cTnI, the immunosensor was incubated in a labeled cTnI secondary antibody solution. The amperometric signal change is then measured at 0.34V (vs. SCE) using o-phenylenediamine and hydrogen peroxide as an electrochemical probe. Response is linear in theconcentration range from 100fg∙mL-1 to 250ng∙mL-1, and the detection limit is 33fg∙mL-1. Graphical abstract Schematic presentation of cardiac troponin I (cTnI) electrochemical immunosensor based on gold nanocube-functionalized graphene oxide (AuNC/GO) as substrate material, bimetallic gold/silver core-shell nanocubes and nitrogen and sulfur co-doped reduced graphene oxide (Au@AgNC/N, S-rGO) as signal amplifier, and hydrogen peroxide (H2O2) and o-phenylenediamine (o-PD) as redox probe.