Sulfur Co-doped Carbon Nanotube Research Articles

Signal amplification strategy based on target-controlled release of mediator for ultrasensitive self-powered biosensing of acetamiprid

Self-powered biosensors with high sensitivity have garnered significant interest for their potential applications in the realm of portable sensing. Herein, a self-powered biosensor with a novel signal amplification strategy was developed by integrating target-controlled release of mediator with an enzyme biofuel cell for the ultrasensitive detection of acetamiprid (ACE). Zeolitic imidazolate framework-67 was utilized as both a nanocontainer for capturing the electron mediator 2,2′-azidobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and a precursor for the synthesis of cobalt nanoparticles/nitrogen, sulfur-codoped carbon nanotubes (Co NPs/NS-CNTs), which were employed as the electrode material for constructing both the glucose oxidase-based bioanode and the laccase-based biocathode. The target analyte ACE can specifically bind to its aptamer, leading to the release of ABTS, which cyclically participates in the catalytic reaction of the biocathode, thereby amplifying the electrochemical signal. By leveraging the benefits of ABTS cyclic catalysis and the effective electrocatalysis of bioelectrodes based on Co NPs/NS-CNTs, the self-powered biosensor has a broad detection range of 0.1–1000 fM and a low detection limit of 25 aM toward ACE. The proposed signal amplification approach presents a promising strategy for enhancing sensitivity and enabling portable analysis in applications of food safety, environmental monitoring, and medical diagnostics.

Nitrogen, phosphorus, and sulfur co-doped carbon nanotubes/melamine foam composite electrode for high-performance vanadium redox flow battery

The high cost and complex modification process of carbon felt electrodes limits its further popularization in vanadium redox flow batteries (VFBs). By introducing low-cost melamine foam, nitrogen, phosphorus, and sulfur co-doped carbon nanotubes/ melamine foam composite electrode (NPS-CNTs-CMF) is designed and fabricated via immersing melamine foam in a solution containing N, P, and S co-doped CNTs. The integration of modified CNTs significantly enhances the conductivity and hydrophilicity of the electrode. Moreover, the composite electrode also demonstrates outstanding electrocatalytic activity owing to the heteroatom doping that further inspired the electrocatalytic activity of CNTs. Density function theory calculations further uncover that introducing heteroatoms on CNTs not only promotes the adsorption of vanadium ions but also facilitates the electron transfer between vanadium ions and MF substrate. As a result, the battery loading with NPS-CNTs-CMF exhibits excellent battery performance, achieving energy efficiency of 80.12 % at 300 mA cm–2. Additionally, the long-term cycling stability is attained over 200 consecutive charge-discharge cycles at 300 mA cm−2. This study provides a novel melamine foam material with low cost and simple modification, and this new composite structure stimulates the development of high-performance electrodes in VFBs.

Insights into the electrocatalytic behavior of nitrogen and sulfur co-doped carbon nanotubes toward oxygen reduction reaction in alkaline media

This study examines the effect of pretreatment and doping to enhance the ORR activity of multiwalled carbon nanotubes (MWCNTs). Melamine and thio-urea are chosen as precursors for mono and co-doping, respectively. A series of samples with pristine and pretreated CNTs are prepared and characterized physicochemically by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) and electrochemically by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The obtained results show that co-doping is an effective way for improving ORR activity, due to the synergistic effect of N and S for changing the charge and spin density, respectively. Moreover, thio-urea favors the proportion of pyridinic and graphitic nitrogen configurations within doped samples. As a consequence, our synthesis method gives samples with superior ORR activity. The maximum ORR activity is obtained for NS-OX-CNTs which shows an over potential of 0.95 V vs RHE at 0.1 mA/cm2, which is comparable to Pt/C (0.98 V vs RHE). The electron transfer number (n) is calculated as 3.9 at 0.4 V which suggests that the ORR proceeds through a dominant 4 e− path. These comparable half-cell results to that of Pt/C pave the way for further testing as cathode materials for anion exchange membrane fuel cells (AEMFC).Graphical abstract

Induced construction of large-area amorphous Li2O2 film via elemental co-doping and spatial confinement to achieve high-performance Li-O2 batteries

In aprotic lithium-oxygen batteries (LOBs), it is hard to simultaneously achieve both high specific capacity and good reversibility with the insulating solid Li2O2 formed via traditional surface or solution route. Tuning the structure of Li2O2 to construct a large-area amorphous film on the surfaces of catalysts is expected to break the above performance limitation. In this work, nitrogen and sulfur co-doped carbon nanotube (CNT) arrays grown on the three-dimensional graphene (NS-CNTA/3DG) was developed as the efficient catalysts for LOBs. Large-area thin amorphous Li2O2 film is induced through the synergistic effect between doping engineering and spatial confinement on CNT arrays, confirmed by theoretical calculation and in-situ Raman examination. Consequently, the NS-CNTA/3DG cathode delivers both high specific capacity (23778 mAh g−1 at 200 mA g−1) and a high round-trip coulombic efficiency (∼87.8%) in the first deep discharge-charge process. This work contributes a new approach to optimize the formation of Li2O2 film, which will inspire the design and fabrication of new catalysts for high-performance LOBs.

Energetic MOF-derived cobalt/iron nitrides embedded into N, S-codoped carbon nanotubes as superior bifunctional oxygen catalysts for Zn–air batteries

Exploring highly effcient bifunctional oxygen catalysts is a central issue for rechargeable Zn–air batteries. Herein, bimetallic cobalt/iron nitrides in situ embedded into nitrogen, sulfur-codoped carbon nanotubes (CoN/FeN@N,S-C-800) was firstly developed by pyrolysis of a Fe-glucosamine coated tetrazole energetic metal − organic framework. Due to the significant nitrogen (5.38at%) dopant content, the synergistic effect between bimetallic nitrides, and interconnected N, S-codoped carbon nanotubes, the as-prepared CoN/FeN@N,S-C-800 exhibits an ultra-high half-wave potential (0.865 V) for oxygen reduction reaction (ORR) and a low overpotential (385 mV) for oxygen evolution reaction (OER). The assembled liquid Zn–air battery affords a high peak power density of 168.3 mW cm−2 and a low voltage gap of 0.55 V after 600 cycles (100 h). Impressively, an all-solid-state ZAB catalyzed by CoN/FeN@N,S-C-800 affords a high OCV of 1.354 V, and three all-solid-state ZABs in series can successfully light LED (~2.2 V), displaying tremendous potentials in portable devices.

Hybrid heterojunction of molybdenum disulfide/single cobalt atoms anchored nitrogen, sulfur-doped carbon nanotube /cobalt disulfide with multiple active sites for highly efficient hydrogen evolution

A multicomponent 3D monolithic electrode was designed that consists of Co single atoms anchored/nitrogen, sulfur co-doped carbon nanotubes (CoSAs-NS-CNTs) on carbon cloth (CC) with ultra-thin MoS2 nanosheets externally decorated and ultra-small CoS2 nanodots internally confined (MoS2/CoSAs-NS-CNTs@CoS2/CC) to form a hybrid heterojunction electrode with double interfaces as vectorial electron transport pathways for promoting electrocatalytic performance. The integration of well-distributed MoS2 nanosheets and CoS2 nanodots linked with Co single atoms anchored/N, S co-doped CNTs endows abundant multiple active sites, outstanding conductivity, and the downshifted d-band center with a thermodynamically favorable hydrogen adsorption free energy (ΔGH*) for effectively catalyzing hydrogen evolution reaction (HER). As a result, the optimal MoS2/CoSAs-NS-CNTs@CoS2/CC electrode exhibits outstanding HER performance with overpotentials of 72 and 56 mV at 10 mA cm−2 and small Tafel slopes of 59.4 and 43.2 mV dec-1 in acidic and alkaline solutions, respectively, outperforming most of the previously reported molybdenum/cobalt sulfide-based electrocatalysts. Moreover, the electrode also displays good durability and stability reflected from the small decrease on activity after 5000 CV cycles and nearly no decay in current density after electrolysis for 20 h.

Experimental and DFT insights into nitrogen and sulfur co-doped carbon nanotubes for effective desulfurization of liquid phases: Equilibrium & kinetic study

Herein, nitrogen and sulfur co-doped carbon nanotubes (NS-CNT) adsorbents were synthesized via the chemical vapor deposition technique at 1000°C by employing the camphor, urea and sulfur trioxide pyridine. In this study, desulfurization of two types of mercaptans (dibenzothiophene (DBT) and tertiary butyl mercaptan (TBM) as nonlinear and linear forms of mercaptan) was studied. In this regard, a maximum capacity of NS-CNT was obtained as 106.9 and 79.4 mg/g and also the removal efficiencies of 98.6% and 88.3% were achieved after 4 h at 298K and 0.9 g of NS-CNT for DBT and TBM, respectively. Characterization of the NS-CNTs was carried out through exploiting scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and elemental analysis (CHN). The isotherm equilibrium data could be ascribed to the Freundlich nonlinear regression form and the kinetic data was fitted by nonlinear form of the pseudo second order model. The negative values of ΔS0, ΔH0 and ΔG0 specify that the adsorption of both types of mercaptans was a natural exothermic process with a reduced entropy. Maintenance of more than 96% of the adsorption capacity even after nine cycles suggest the NS-CNT as a superior adsorbent for mercaptans removal in the industry. Density functional theory (DFT) calculations were also performed to peruse the effects of S/N co-doping and carbon monovacancy defects in CNTs toward the adsorption of DBT and TBM.

Rational Fabrication of Nitrogen and Sulfur Codoped Carbon Nanotubes/MoS2 for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries are more promising and attractive than lithium-ion batteries owing to a higher charge-storage capacity. However, their commercial applications are hindered by an undesirable polysulfide shuttling effect during the cycling procedure. Herein, nitrogen and sulfur codoped carbon nanotubes intertwined with flower-like molybdenum disulfide (NSCNTs/MoS2 ) were synthesized by using a feasible hydrothermal method and used as effective lithium polysulfides (LiPSs) tamers. The NSCNTs/MoS2 had a strong hybrid structure with strong interfacial interactions for physical confinement, chemical adsorption, and electrocatalytic conversion of intermediate LiPSs during the charge-discharge process. The NSCNTs intensified the flexibility and constructed a conductive framework for rapid ion/electron transfer, whereas the electrocatalysis of MoS2 managed the sulfur reaction chemistry in two ways: it chemically immobilized LiPSs through Li-S bonds and kinetically sped up the sulfur redox reactions. Owing to these merits, the Li-S cell with a NSCNTs/MoS2 host and NSCNTs/MoS2 -coated separator (NSCNTs/MoS2 /S-NM) exhibited a high reversible capacity of 814 mAh g-1 at 1.0 C and long-lasting cycling durability with an ultralow capacity decay of 0.02 % per cycle over 1000 cycles. Accordingly, rationally integrating the concepts of physical immobilization, chemical capture, and electrocatalysis to establish a multifaced cell structure for the architecture of high-performance Li-S batteries is a significant strategy.

Controllable active sites and facile synthesis of cobalt nanoparticle embedded in nitrogen and sulfur co-doped carbon nanotubes as efficient bifunctional electrocatalysts for oxygen reduction and evolution reactions

Abstract Development of efficient and promising bifunctional electrocatalysts for oxygen reduction and evolution reactions is desirable. Herein, cobalt nanoparticles embedded in nitrogen and sulfur co-doped carbon nanotubes (Co@NSCNT) were prepared by a facile pyrolytic treatment. The cobalt nanoparticles and co-doping of nitrogen and sulfur can improve the electron donor-acceptor characteristics of the carbon nanotubes and provide more active sites for catalytic oxygen reduction and evolution reactions. The prepared Co@NSCNT, annealed at 900 °C, showed excellent electrocatalytic performance and better durability than commercial platinum catalysts. Additionally, Co@NSCNT-900 catalysts exhibited comparable onset potentials and Tafel slopes to ruthenium oxide. Overall, Co@NSCNT showed high activity and improved durability for both oxygen evolution and reduction reactions.

Synthesis of multi-walled phosphorus and sulfur co-doped CNTs

Phosphorous and sulfur co-doped carbon nanotubes (PSCNTs) has prepared from the catalytic chemical vapor deposition (CVD) method, starting from available materials and cheap catalyst. Triphenyl phosphine and sulfur were applied in first zone and the catalyst applied in second zone to prepare the product from acetylene gas at 720 °C. The structure of product was confirmed using field emission scanning electron microscopy (FESEM) and the presence of phosphorous and sulfur atoms was defined using energy-dispersive X-ray spectroscopy (EDS) method. Thermal behavior of the prepared PSCNT was analyzed from thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in 25–890 °C, showing total 25% weight loss. Moreover, XRD patterns and Raman spectrum were obtained to define more properties of the product. Finally, the electrocatalytic ability of the prepared PSCNT in oxygen reduction reaction (ORR) was analyzed using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) diagrams. The obtained diagrams showed appropriate catalytic activity in the ORR region.

Cobalt encapsulated in the nitrogen and sulfur co-doped carbon nanotube supported platinum for the oxygen reduction reaction catalyst

In this paper, cobalt encapsulated in nitrogen and sulfur co-doped carbon nanotube (Co-NST) was synthesized through a simple pyrolysis method to impregnate platinum (Pt) nanoparticles. The Co-NST presented a bamboo-like morphology with the high degree of graphitization. Owing to the dual heteroatoms co-doped in the carbon matrix, the Pt supported on the Co-NST (Pt/Co-NST) showed the well-dispersed morphology of the Pt nanoparticles. In addition, the synergistic effect between the Co-NST support and the Pt nanoparticle was observed from the physicochemical characterizations. As a result, the Pt/Co-NST presented improved oxygen reduction reaction (ORR) activity and stability compared to the commercial Pt/C. The mass activity and specific activity of the Pt/Co-NST presented 508.48 mA mgPt−1 and 723.93 μA cmPt−2, respectively, which exhibited more than 3 times higher compared to those of the commercial Pt/C. After repeating 5000 potential cycles, the Pt/Co-NST showed improved stability with 29 mV loss in half-wave potential, while the half-wave potential of the commercial Pt/C was severely decreased by 118 mV.

Dendrite-Free Sodium-Metal Anodes for High-Energy Sodium-Metal Batteries.

Sodium (Na) metal is one of the most promising electrode materials for next-generation low-cost rechargeable batteries. However, the challenges caused by dendrite growth on Na metal anodes restrict practical applications of rechargeable Na metal batteries. Herein, a nitrogen and sulfur co-doped carbon nanotube (NSCNT) paper is used as the interlayer to control Na nucleation behavior and suppress the Na dendrite growth. The N- and S-containing functional groups on the carbon nanotubes induce the NSCNTs to be highly "sodiophilic," which can guide the initial Na nucleation and direct Na to distribute uniformly on the NSCNT paper. As a result, the Na-metal-based anode (Na/NSCNT anode) exhibits a dendrite-free morphology during repeated Na plating and striping and excellent cycling stability. As a proof of concept, it is also demonstrated that the electrochemical performance of sodium-oxygen (Na-O2 ) batteries using the Na/NSCNT anodes show significantly improved cycling performances compared with Na-O2 batteries with bare Na metal anodes. This work opens a new avenue for the development of next-generation high-energy-density sodium-metal batteries.

Urchin-like non-precious-metal bifunctional oxygen electrocatalysts: Boosting the catalytic activity via the In-situ growth of heteroatom (N, S)-doped carbon nanotube on mesoporous cobalt sulfide/carbon spheres

We successfully design and construct urchin-like non-precious-metal bifunctional oxygen electrocatalysts via a two-step pyrolysis process, where nitrogen, sulfur co-doped carbon nanotube frameworks are grafted onto mesoporous cobalt sulfide/nitrogen, sulfur co-doped carbon spheres. The urchin-like structure grants large electrochemically active area, good electron and mass transfer capability, as well as excellent structural stability. Nitrogen, sulfur co-doped carbon can synergistically enhance the catalytic activity of cobalt sulfide sites, and also contribute to the exposure of heteroatom-induced active sites, such as, pyridinic N, graphitic N, and C-S-C. Hence, benefiting from the unique architecture and efficient catalytic sites, the resulting catalysts demonstrate excellent bifunctional catalytic activities with a positive half-wave potential of 0.860 V vs. RHE for oxygen reduction reaction and low overpotential of ∼390 mV at the current density of 10 mA cm−2 for oxygen evolution reaction in alkaline medium, which can rank them among one of the most promising cobalt-based bifunctional oxygen electrocatalysts reported previously.

Electrocatalytic Activity of a 2D Phosphorene-Based Heteroelectrocatalyst for Photoelectrochemical Cells.

Research into efficient synthesis, fundamental properties, and potential applications of phosphorene is currently the subject of intense investigation. Herein, solution-processed phosphorene or few-layer black phosphorus (FL-BP) sheets are prepared using a microwave exfoliation method and used in photoelectrochemical cells. Based on experimental and theoretical (DFT) studies, the FL-BP sheets are found to act as catalytically active sites and show excellent electrocatalytic activity for triiodide reduction in dye-sensitized solar cells. Importantly, the device fabricated based on the newly designed cobalt sulfide (CoSx ) decorated nitrogen and sulfur co-doped carbon nanotube heteroelectrocatalyst coated with FL-BP (FL-BP@N,S-doped CNTs-CoSx ) displayed an impressive photovoltaic efficiency of 8.31 %, outperforming expensive platinum based cells. This work paves the way for using phosphorene-based electrocatalysts for next-generation energy-storage systems.

Development of cobalt encased in nitrogen and sulfur co-doped carbon nanotube for non-precious metal catalyst toward oxygen reduction reaction

Development of cobalt encased in nitrogen and sulfur co-doped carbon nanotube for non-precious metal catalyst toward oxygen reduction reaction

One step in-situ synthesis of Co@N, S co-doped CNTs composite with excellent HER and ORR bi-functional electrocatalytic performances

Heteroatoms such as nitrogen/sulfur atoms are efficient for boosting the electrocatalytic performances of carbon materials. Meanwhile, loading transition metals/metal compounds on carbon materials also can significantly enhance the electrocatalytic activities of carbon materials. Despite the high electrocatalytic activities and broad applications of nitrogen, sulfur co-doped carbon nanotubes (CNTs) composites according to the reported literature, the synthesis processes of them are relatively complex. Herein, for the first time we report a facile method to synthesize Co encapsulated, N, S co-doped CNTs (Co-NSCNTs) composite using thiourea and cobalt acetate through heat treatment. These kinds of CNTs are actually curled and stacked by multiple layers of N, S co-doped nanosheets, which possess an unenclosed structure and thereby a very large specific surface area (276.2m2g−1). Most of the Co nanoparticles (∼30nm) are well encapsulated inside the N, S co-doped CNTs, forming a unique Co, N, S tri-doped CNTs composite. In this composite, the doping amount of N and S atoms reaches 8.1 and 2.2 at.% (from XPS results) respectively and the Co element reaches 8.45wt.% (ICP). Owing to the special structure and composition, the Co-NSCNTs exhibit very high catalytic performances towards HER and ORR in both acidic and alkaline electrolytes.

Facile and scalable synthesis of coal tar-derived, nitrogen and sulfur-codoped carbon nanotubes with superior activity for O2 reduction by employing an evocating agent

Nitrogen and sulfur-codoped carbon nanotubes were synthesized with coal tar as nitrogen and sulfur precursors by employing the evocating agent of dicyandiamide. Resultant samples exhibited superior activities for the oxygen reduction reaction in both acidic and alkaline media.