Sulfur Co-doping Research Articles

Carbon-based 0D/1D/2D assembly with desired structures and defect states as non-metal bifunctional electrocatalyst for zinc-air battery

For the design of electrocatalysts, the combination between components and the regulation of material structures tend to be neglected, giving rise to the constraint of catalytic performance and durability. Herein, we developed a graphene oxide quantum dots (GOQDs) with enhanced oxygen content by a one-step cutting method. Then, one-dimensional (1D) carbon nanotubes and two-dimensional (2D) reduced graphene oxide are crosslinked and self-assembled, thus attracting unsaturated-bond-riches GOODs (0D) to uniformly attach to the skeleton, simultaneously achieving nitrogen and sulfur co-doping. To the best of our knowledge, there is no report to prepare bifunctional electrocatalyst with GOQDs. Electrochemical tests show that even without metal-doping, the novel non-metal bifunctional electrocatalyst (N,S-GOQD-RGO/CNT) exhibits a higher half-wave potential (0.84 V) and enhanced limiting current density (5.88 mA cm−2) than commercial Pt/C catalyst. The density functional theory is implemented to reveal the coordination of nitrogen and sulfur co-doping on GOQDs, which results in the improvement of overall catalytic active sites. Furthermore, the rechargeable zinc-air battery based on N,S-GOQD-RGO/CNT exhibits a maximum power density of 134.3 mW cm−2, open circuit potential of 1.414 V, which is better than Pt/C+Ru/C mixed material. The obtained N,S-GOQD-RGO/CNT will provide a perspective application in fuel cells.

One-Step Synthesis of the Nitrogen and Sulfur Codoped Carbon Dots for Detection of Lead and Copper Ions in Aqueous Solution

Herein, by using the green and cheap L-cysteine as the precursor, nitrogen and sulfur codoped carbon dots (NS-CDs) were synthesized via a facile one-step hydrothermal method. The obtained NS-CDs showed the relatively narrow size distributions (2.1~3.9 nm) with the lattice spacing of 0.29 nm, as well as the excitation-dependent photoluminescence (PL) emission activity with the quantum yield (QY) of 18%. More interestingly, the PL intensity of NS-CDs was quenched by the addition of copper or lead ions (Cu2+ or Pb2+), which was shown in the tradition detection method by PL spectra. The NS-CDs exhibited ultrasensitive colorimetric sensing capability for both Cu2+ and Pb2+ by the color variance using naked eyes without any further treating. Two different coupling ways for detecting Pb2+ and Cu2+ were induced by the analysis of the Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). And the as-prepared NS-CDs showed their potential application in the heavy metal ions detection for the wastewater determination.

Facile self-templating synthesis of layered carbon with N, S dual doping for highly efficient sodium storage

Nitrogen and sulfur co-doping is emerging as a promising approach to prominently improve the sodium storage performance of carbonaceous materials. However, poisonous chemicals and rigorous conditions are normally involved in their preparation, especially in the sulfidation process. Therefore, developing novel, facile and eco-friendly approaches to construct nitrogen and sulfur co-doped carbon (NSC) is still challenging. In this work, a facile self-templating synthesis method is reported to allow the simple and green preparation of NSC. Particularly, small-molecule dithiooxamide can be directly converted to NSC through a facile thermal condensation process, serving as precursor, template, and self-doping agent simultaneously. In account of its high ionic and electronic conductivity, increased interlayer spacing, unique layers assembled structure and efficient N, S co-doping, the NSC obtained at 800 °C exhibits excellent sodium storage performances, including prominent reversible capacity (316.1 mAh g−1 at 0.1 A g−1 up to 100 cycles), remarkable rate capability (178.3 mAh g−1 at 3 A g−1), and robust stability upon long-term cycling (213.6 mAh g−1 at 1 A g−1 up to 2000 cycles), rendering itself to be a promising candidate for practical sodium-ion battery.

Nitrogen and Sulfur Codoped Graphene Macroassemblies as High-Performance Electrocatalysts for the Oxygen Reduction Reaction in Microbial Fuel Cells

Microbial fuel cells (MFCs) are receiving considerable attention for generating clean and sustainable electrical energy directly from wastewater. The development of highly efficient, durable, and i...

Nitrogen, Sulfur Co-Doped Hierarchically Porous Carbon as a Metal-Free Electrocatalyst for Oxygen Reduction and Carbon Dioxide Reduction Reaction.

High-cost and low-efficiency electrocatalysts have hindered oxygen reduction reaction (ORR) in fuel cells and CO2 reduction reaction (CO2RR) for producing fuels and value-added chemicals. Here, a low-cost metal-free electrocatalyst of a N, S co-doped hierarchically porous carbon (NSHPC) for efficient ORR and CO2RR is reported. The NSHPC is prepared by pyrolysis of glucosamine hydrochloride and thiocyanuric acid precursors using SiO2 as hard templates. The N, S co-doping effectively enhances catalytic activity and selectivity, and the hierarchically porous structure largely exposes abundant active sites to reaction species and facilitates electrolyte transport, thereby leading to significantly increased catalytic activities for the NSHPC. The resultant NSHPC exhibits excellent electrocatalytic activities toward ORR in both acidic and alkaline electrolytes and also shows application in proton exchange membrane fuel cells (PEMFCs). More importantly, the NSHPC enables CO2 reduction to CO with 87.8% maximum Faraday efficiency (FE) in aqueous electrolytes. This work offers a novel insight into the development of multifunctional electrocatalysts for producing electricity, fuels, and value-added chemicals.

Up-Scalable Conversion of White-Waste Polystyrene Foams to Sulfur, Phosphorus-Codoped Porous Carbon for High-Performance Lithium–Sulfur Batteries

Discarded polystyrene foams as white wastes, at least two million tons in demand annually in China, are threatening environment and health because of their formidable degradation, which increase in quantity with a reported rate of about 15% per year. Here, we employ a facile and up-scalable approach to convert discarded polystyrene foams to S,P-codoped porous carbon (SPPC) as the effective sulfur mobilizer for lithium–sulfur batteries. The high porosity of SPPC can ensure high loading of sulfur with effective physical adsorption to polysulfides, and the heteroatom codoping of sulfur and phosphorus can enhance the electrical conductivity of carbon effectively with strong chemical immobilization for polysulfides. These effects are together responsible for the superior performance of S@SPPC with a sulfur loading of 72 wt %. The S@SPPC cathode with an areal sulfur loading of 2 mg cm–2 exhibits an initial capacity of 893 mA h g–1 at 2 C with only a small capacity loss of 0.049% per cycle over 800 cycles. The cathode still exhibits both superior rate capability, and stable cycling performance for a capacity decay rate of 0.06% per cycle over 600 cycles at 2 C by increasing the areal sulfur loading to 4.8 mg cm–2 and a capacity of 694 mA h g–1 retained after 150 cycles for 0.5 C at a much reduced electrolyte-to-sulfur ratio of 5 mL g–1. This study offers a route for realizing the up-scalable conversion of “waste” to “treasure,” which is significant for practical applications in energy storage.

Sulfur and phosphorus co-doped hard carbon derived from oak seeds enabled reversible sodium spheres filling and plating for ultra-stable sodium storage

Hard carbon has been considered as a promising anode material for sodium ion batteries (SIBs), while suffers from poor rate performance and some safety issues caused by irreversible or undesirable sodium plating. Heteroatom doping is an effective strategy to further improve the electrochemical performance of hard carbon. Herein, biomass oak seeds are selected as carbon source to prepare S/P co-doped hard carbon through a simple one-step pyrolysis process. The hard carbon pyrolyzed from oak seeds at 1000 °C (C1000) exhibits excellent rate performance (initial discharge capacity is 136.1 mA h g−1) and remarkable cycling stability (1000 cycles with 88% capacity retention at 1000 mA g−1). The unique S/P co-doping is very important to the high electrochemical performances, since sulfur and phosphorus co-doping enlarges interlayer distance, modifies the electronic structure, as well as provides more effective active sites, thereby enabling hard carbon with a fast, complete charge transfer kinetics of sodium storage.

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.

An experimental investigation on the sulfur and nitrogen co-doping and oxidation of prepared graphene by electrochemical exfoliation of pencil graphite rods

In this research, the electrochemical exfoliation of pencil rods was carried out for the synthesis of graphene sheets in different mixtures of H2SO4 and HNO3 solution. Influence of different volume ratios of H2SO4: HNO3 at a low concentration (0.6 M) on the morphology and structure of prepared graphene sheets was investigated by field emission electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Raman spectroscopy and atomic force microscopy (AFM) analyses. Results indicated that the mixtures of few-layered graphene, multi-layered graphene, and graphene oxide were achieved by applying an anodic voltage of +10 V. However, the number of layers, degree of oxidation and defect density of the synthesized powders were different. By increasing the volume ratio of HNO3 in electrolytes, the degree of exfoliation of graphite decreased. On the other hand, the highest degree of oxidation was achieved for the prepared graphene by electrochemical method in the mixture of H2SO4: HNO3 with 1:1 ratio. EDS results of the prepared powders demonstrated the occurrence of nitrogen and sulfur co-doping of graphene sheets.

Phosphorus and Sulfur Co-Doped Cobaltous Oxide Synthesized by an Inorganic-Salt-Assisted Method: Reaction Mechanism and Electrocatalytic Application.

An inorganic-salt-assisted synthesis of non-metallic heteroatom (phosphorus and sulfur) co-doped cobaltous oxide (P/S-CoO) has been reported. Potassium sulphate (K2 SO4 ) was used as inorganic source of sulfur (S), while triphenyl phosphine (PPh3 ) was used as phosphorus (P) source. A stepwise mechanistic investigation into the doping process revealed that the decomposition of PPh3 triggered the release of both the elemental sulfur and phosphorus because of the reducing reaction environment. The transformation of cobalt-PPh3 complex into cubic cobalt (II) oxide along with the successful co-doping (P and S) was achieved by high temperature calcination at 800 °C but preserved the bulk CoO crystalline structure. The as synthesized P/S-CoO demonstrated an unprecedented enhancement on the oxygen evolution activity compare to that of pristine CoO with the current density of 10 mA/cm2 at the overpotential of 293 mV in 1.0 M KOH electrolyte and profound stability at different current densities.

Synergetic effect of nitrogen and sulfur co-doping in mesoporous graphene for enhanced energy storage properties in supercapacitors and lithium-ion batteries

Nitrogen and sulfur co-doped mesoporous graphene (NSMG) was fabricated via a hydrothermal method followed by heat treatment utilizing graphite oxide (GO), tri-block co-polymer P123 and thiourea as the N and S source. The porous structure of the NSMG was controlled by heat treatment at 600 ​°C and 800 ​°C thus obtaining NSMG600 and NSMG800 which had specific surface areas of 966 and 1335 ​m2 ​g−1, respectively. X-ray photoelectron spectroscopy (XPS) of the NSMGs demonstrated the presence of active pyridinic-N, pyrrolic-N, graphitic-N, pyridinic N- oxide, thiophene and –SOx groups in the structure. The N and S contents and configurations were controlled by annealing temperature hence influencing the performance in supercapacitors (SC) and lithium-ion batteries (LIBs). There was improved electrolyte ion mobility and lithium-ion diffusion for both SCs and LIBs respectively. The improved performance could be attributed to the unique structural features such as plentiful defects, wrinkles, abundant pores, and N/S co-doping. NSMG600 exhibited the highest capacitance of 261 ​F ​g−1 at 0.5 ​A ​g−1 in SCs while NSMG800 showed the best performance in LIBs with a discharge capacity of 460 mAh g−1 at 100 ​mA ​g−1 with good cycling stability (440 mAh g−1) and superior rate capability. Thus NSMGs exhibit potential application in high-performance energy storage devices.

An efficient pseudocapacitor electrode material with co-doping of iron (II) and sulfur in luminescent graphene quantum dots

An efficient electrode material (Fe (II)S-GQDs) has been prepared by co-doping of sulfur and iron atoms with Graphene quantum dots. A top down synthesis method including a facile and one-pot hydrothermal was used to develop high capacity and good stability electrode material by selecting ferrous sulphate powder (FeSO4.7H2O) and graphene oxide (GO) as a precursor material. The results obtained from TEM measurements reveal the size alters from micrometer graphene sheets of GO to nano-meter dots for GQDs and Fe (II)S-GQDs. The electrochemical studies reveal that Fe(II) S doped GQDs can exhibit a reversible redox reaction with excellent specific capacitance of 476.2 F/g as compared to that of GQDs (143F/g). It has been found that there is an improvement in electrical conductivity and electron transfer in addition to the largest charge storage capacity. More remarkably, the doped electrode material shows a small charge transfer resistance (Rct) value (30 Ω) in case of Fe(II)S-GQDs as compared to GQDs (2.5 kΩ) due to fast diffusion of ion and electron between working electrodes and electrolyte.

Facile Synthesis of Bi2MoO6 Nanosheets@Nitrogen and Sulfur Codoped Graphene Composites for Sodium-ion Batteries

Recently, sodium-ion batteries gradually become the promising alternative to lithium-ion batteries because of cost considerations. In this work, a kind of Bi2MoO6 nanosheets@N,S codoped graphene composite is designed and fabricated for sodium storage applications. Detailed characterizations are employed to investigate its morphology, structure and chemical compositions. When evaluated as an anode material for sodium-ion batteries, the as-prepared composite is able to display a specific capacity of 254 mA·h/g after 50 cycles at a current density of 0.2 A/g, and 186 mA·h/g at 1.6 A/g during the rate capability test. As a result, the further morphology and structure optimization is still required for high performance sodium-ion batteries.

Carbon source self-heating: ultrafast, energy-efficient and room temperature synthesis of highly fluorescent N, S-codoped carbon dots for quantitative detection of Fe(iii) ions in biological samples.

In recent years, photoluminescent (PL) carbon dots (CDs) have attracted enormous attention because of their many fascinating properties. However, the traditional synthesis routes of PL CDs usually suffer from relatively low quantum yields (QYs) and require complicated operation processes as well as lots of externally supplied energy. Herein, we report a room temperature, green, ultrafast and energy-efficient route for large scale synthesis of highly PL N, S-codoped CDs without any external energy supply. The N, S-codoped CDs are prepared through a novel carbon source self-heating strategy, using the sole precursor tetraethylenepentamine (TEPA) simultaneously as the carbon, nitrogen and heat source, triggered by the heat initiator sodium persulfate (Na2S2O8). The large amount of heat released from Na2S2O8-triggered oxidation of TEPA could effectively promote the spontaneous polymerization and carbonization of TEPA precursors themselves as well as the in situ co-doping of sulfur, which had marked synergistic effects on the fluorescence enhancement of CDs, eventually leading to the high-yield (58.0%) preparation of highly fluorescent N, S-codoped CDs (QY 26.4%) at room temperature within 2 min. Moreover, the fluorescence of N, S-codoped CDs could be selectively quenched by Fe3+ ions in the presence of EDTA, in an ultra-wide range of 0.2–600 μM, with a detection limit of 0.10 μM. Ultimately, the fluorescent nanoprobe was successfully used for the quantitative detection of Fe3+ in human serum samples, indicating its great potential for sensing and biomedical applications.

Tailoring of nitrogen-vacancy colour centers in diamond epilayers by in situ sulfur and nitrogen anion engineering

In this work, a sulfur and nitrogen co-doping technique has been demonstrated for diamond epilayer growth by microwave plasma chemical vapor deposition (MPCVD). Results show that the nitrogen concentration in films could be tailored by co-doping of sulfur. At a certain growth condition, single nitrogen-vacancy (NV) colour centers could be achieved. A competition mechanism between sulfur and nitrogen incorporation in the H2/CH4 plasma is proposed to explain the efficient suppression of the incorporated nitrogen. Briefly, adding H2S decreases the growth rate and the resulting (S or S2) species could react with the dissociated nitrogen atoms to form S and N-containing clusters. Hence, the concentration of the NV centers in diamond is decreased. Meanwhile, density functional theory (DFT) calculations indicate an increment of the NV formation energy in the presence of sulfur, which confirms that sulfur has a suppression effect on the formation of the NV centers. This study provides a new method to adjust the concentration of the NV centers in the diamond films.

Pencil-drawing on nitrogen and sulfur co-doped carbon paper: An effective and stable host to pre-store Li for high-performance lithium–air batteries

Metallic lithium (Li) is regarded as the ultimate anode for high-energy-density rechargeable batteries due to its highest theoretical capacity and most electronegative potential. However, there are serious challenges before practical application of Li metal batteries (e. g. Li–air batteries), including the dendritic Li formation and infinite variation of electrode dimension. Herein, nitrogen (N) and sulfur (S) co-doping carbon paper (NS-CP) is synthesized and further modified with a graphite-based layer (GL) by pencil-drawing. The as-prepared GL modified NS-CP (GL/NS-CP) is applied to pre-store Li through the heating-infusion method and Li-GL/NS-CP electrode is obtained. Experimental and theoretical results have demonstrated that N, S co-doping can effectively enhance the lithiophilicity of CP to ensure the uniform Li deposition. In addition, GL presents excellent Li wettability to rapidly syphon molten Li. Moreover, abundant pores in GL/NS-CP can accommodate enough Li to alleviate electrode volume change and lower local current density to restrain Li dendrites. Compared with pure Li anode, Li-GL/NS-CP electrode shows more stable voltage curves with lower overpotential (20 ​mV for 600 cycles). As a result, Li–air batteries with Li-GL/NS-CP anodes also exhibit the satisfying cycling life. These results have shed a new light on the development of Li anodes.

Sulphur and nitrogen co-doped graphene-based electrocatalysts for oxygen reduction reaction in alkaline medium

It is highly desirable to synthesise heteroatom-doped carbon-based materials in an environmentally friendly and simple way, which possess good electrocatalytic activity towards the oxygen reduction reaction (ORR). Therefore, in this study, we focused on comparing sulphur and nitrogen co-doped graphene-based materials prepared using simple synthesis procedures as ORR electrocatalysts. In particular, we considered two different sulphur and nitrogen precursors (thiosemicarbazide and trithiocyanuric acid) and either dry ball-milling or a wet method based on sonication followed by pyrolysis at 800 °C for S,N-co-doping of graphene. Electrochemical investigation of the S,N-co-doped catalysts using the rotating disc electrode (RDE) method showed superior ORR activity compared to the undoped graphene material, which is due to the synergetic effect of sulphur and nitrogen co-doping as well as to the defects present in the catalysts.

Synthesis and characterization of photocatalytically active crumpled-shape nanocomposites of nitrogen and sulfur co-doped ZnO–CeO2

In this study, crumpled-shape nanocomposite of nitrogen and sulfur co-doped ZnO–CeO2 (NSZC) was deposited on FTO substrate using one-step ultrasonic spray pyrolysis. Zinc acetate, cerium nitrate, and thiourea were dissolved in deionized water and used as starting solution. The samples were characterized using FESEM, XRD, UV–vis spectroscopy, EIS, and PL. The as-prepared nitrogen and sulfur co-doped ZnO–CeO2 nanocomposites were evaluated as high photocatalysts for degradation of methyl orange. Nearly 100% photocatalytic degradation of methyl orange was achieved for 180 min. The photoluminescence and electrochemical impedance spectroscopy revealed that co-doping of nitrogen and sulfur could promote the suppression of electron-hole recombination.

Iron and sulfur co-doped graphite carbon nitride (FeOy/S-g-C3N4) for activating peroxymonosulfate to enhance sulfamethoxazole degradation

In this study, the iron and sulfur co-doped graphite carbon nitride (FeOy/S-g-C3N4) was easily prepared by one-step pyrolysis using thiourea and ferric chloride hexahydrate as precursors and applied to activate peroxymonosulfate (PMS) for the degradation of sulfamethoxazole (SMX). The characterization results showed that iron existed as Fe2O3 and Fe3O4. Partial nitrogen atoms in the frame of g-C3N4 were substituted by sulfur atoms. FeOy/S-g-C3N4 can effectively activate PMS to produce sulfate radicals, hydroxyl radicals and singlet oxygen contributing to the SMX degradation. According to the density functional theory (DFT) calculation, the co-doping of iron and sulfur altered the charge density and its distribution of g-C3N4 surface, which enhanced the PMS activation. The effect of initial concentrations of SMX and PMS, pH, temperature and inorganic ion concentrations on SMX degradation was investigated. 0.8 mM of PMS could degrade up to 10 mg/L of SMX. The initial pH had no obvious effect on the SMX degradation. Higher temperature accelerated the SMX degradation, and the activation energy was calculated to be 43.7 kJ/mol. The effect of inorganic ions was dependent on their initial concentration. Based on the comparison of XPS spectrum before and after reaction, the decreased catalytic activity of FeOy/S-g-C3N4 after five cycle reuse was due to the breakdown of surface functional groups. Seven intermediate products were identified, and the possible degradation pathway was proposed. This study could provide a facile and cost-effective method to synthesize the efficient activator of PMS, and a mechanistic insight into PMS activation by FeOy/S-g-C3N4 for the degradation of emerging pollutants in water and wastewater.

Platelet Nitrogen and Sulfur Co-Doped Ordered Mesoporous Carbon with Inexpensive Methylene Blue as a Single Precursor for Electrochemical Detection of Herbicide Amitrole

Heteroatom-doped ordered mesoporous carbons (OMCs) have currently been considered as promising electrode materials for electrochemical sensors due to the combined advantages of ordered mesoporous materials and heteroatom-doped carbon materials. Herein, a novel nitrogen and sulfur co-doped OMCs (N,S-OMC) has been prepared via a nanocasting strategy with an inexpensive methylene blue as single precursor. The obtained mesoporous carbon has platelet morphology, short mesoporous channel together with a large surface area (549[Formula: see text]m2/g) as well as rich N- and S-containing functional groups (6.8[Formula: see text]at.% N and 2.3[Formula: see text]at.% S). Compared with the graphene (GR) and carbon nanotube (CNT) electrode material, the N,S-OMC exhibited a higher electrochemical activity towards the oxidation of herbicide amitrole, ascribable to N,S-OMC’s open mesoporous structures and abundant electroactive defect sites on the carbon skeleton. And, an amitrole electrochemical sensor with N,S-OMC modified electrode as working electrode was fabricated, exhibiting a good selectivity, stability, reproducibility and wide linear range of 3–750[Formula: see text][Formula: see text]M. Moreover, the N,S-OMC-based electrochemical sensor was proved feasible in river water sample analyses, showing a satisfied recovery ranging from 97.03% to 105.42%. The results not only demonstrate cheap methylene blue can be used as single precursor for the N,S-OMC preparation, but also confirm the N,S-OMC is promising in amitrole sensor fabrication.