Nitrogen-doped Carbon Nanotube Arrays Research Articles

Metal-encapsulated nitrogen-doped carbon nanotube arrays electrode for enhancing sulfion oxidation reaction and hydrogen evolution reaction by regulating of intermediate adsorption

For treatment of sulfion-containing wastewater, coupling the electrochemical sulfion oxidation reaction (SOR) with hydrogen evolution reaction (HER) can be an ideal way for sulfur and H2 resources recovery. Herein, we synthesize a metal-modified carbon nanotube arrays electrode (Co@NCNTs/CC) for SOR and HER. This electrode has excellent performance for SOR and HER attributed to the unique array structure. It can achieve 99.36 mA/cm2 at 0.6 V for SOR, and 10 mA/cm2 at 0.067 V for HER. Density functional theory calculations verify that metal modification is able to regulate the electronic structure of carbon nanotube, which is able to optimize the adsorption of intermediates. Employed Co@NCNTs/CC as bifunctional electrodes to establish a hybrid electrolytic cell can reduce about 67% of energy consumption compared with the traditional water splitting electrolytic cell. Finally, the hybrid electrolytic cell is used to treat actual sulfion-containing wastewater, achieving the sulfur yield of 30 mg h−1 cm−2 and the hydrogen production of 0.64 mL/min.

Editable 3D Micro-Supercapacitor with High Energy Density Based on Mortise–Tenon Joint Structures

Three-dimensional micro-supercapacitors (3D MSCs) have accelerated the development of microenergy-storage modules for miniaturized and portable electronics. However, the low energy density, complex construction strategy, and low assembly accuracy of a 3D MSC restrict its practical application. Herein, we design a simple construction strategy for a 3D MSC with high energy density by mortise and tenon structures. Wood-derived carbon modified by nitrogen-doped carbon nanotube arrays (N-CNT-WDC) provides an ordered ion transport channel and a large active specific surface area, availing the improvement of the energy density of a 3D MSC. Its strong carbon skeleton structure supports the construction of 3D interdigital electrodes with a tenon structure by laser, realizing precise and regulable assembly of 3D MSCs through a mortise and tenon joint. The prepared 3D MSC based on N-CNT-WDC shows an excellent volumetric capacitance of 93.66 F cm-3, a high volumetric energy density of 12 mW h cm-3 at 600 mA cm-3, and an 85% retention rate of capacitance after 10,000 cycles of charge and discharge at 1000 mA cm-3. Furthermore, the mortise and tenon structure realizes diversified integration of 3D MSCs, making the integrated manufacturing of 3D microdevices more convenient and promoting their application in microelectronic devices.

In-situ cobalt-nickel alloy catalyzed nitrogen-doped carbon nanotube arrays as superior freestanding air electrodes for flexible zinc-air and aluminum-air batteries

A flexible air electrode with excellent activity and outstanding stability is highly desirable for metal-air batteries. Herein, the rational design of CoNi alloys derived intertwined N-doped carbon nanotube arrays onto carbon cloth (CoNi@NCNTs/CC) is reported, as self-supported air electrodes for flexible zinc-air and aluminum-air batteries. CoNi@NCNTs/CC exhibits a low potential of 1.56 V at 10 mA cm−2 in OER, along with a half-wave potential of 0.82 V in ORR, which is attributed to abundant active sites including CoNi alloys with optimized adsorption energy, Co/Ni-Nx and N-doped CNTs. The well-designed nanotube array construction with substantial channels on carbon cloth facilitates the mass diffusion and electron delivery, and improves mechanical flexibility. Combining excellent activity and promising flexibility, CoNi@NCNTs/CC based liquid- and all-solid-state zinc-air batteries exhibit excellent charge/discharge capability and long-term stability. And the liquid- and all-solid-state aluminum-air batteries deliver promising discharge property with a high open circuit voltage as well as commendable flexibility.

Flexible and waterproof nitrogen-doped carbon nanotube arrays on cotton-derived carbon fiber for electromagnetic wave absorption and electric-thermal conversion

• Flexible and waterproof NCNT arrays on carbon fiber (NCNT@CF) were fabricated. • NCNT@CF exhibited excellent EMW absorption performances. • The R L,min value and EAB 10 of NCNT@CF are − 57.8 dB and 4.5 GHz, respectively. • RCS values of the materials were simulated under real far field conditions. • NCNT@CF had flexible, waterproof, and electric-thermal conversion functions. It is highly desirable, but challenging to develop multi-functional electromagnetic wave (EMW) absorbing material for practical applications in some special environments. Herein, we successfully fabricated cobalt-nanoparticle-embedded N-doped carbon nanotube arrays on the carbonized cotton fiber cloth as multifunctional material with an excellent EMW absorption, flexibility, hydrophobicity, and electric-thermal performance. The excellent multifunction benefits from high conductivity, large specific surface area, abundant N dopants, and three-dimensional open porous features. Minimal reflection loss and efficient absorption bandwidth of the optimized material as EMW absorbers can reach − 57.8 dB and 4.5 GHz, respectively, which are better than most reported carbon-based absorbers. Meanwhile, theoretical simulations of the radar cross-sectional (RCS) further confirm that the multifunctional material has excellent EMW attenuation performance and potential in practical application. Moreover, the materials possess strong hydrophobicity and high electrical conductivity, endowing them with other attractive functions of self-cleaning and good electric thermal performance, which expand the potential applications range of EMW absorption materials. Our present method can be extended to design next-generation EMW absorbing materials with multifunctionalities for practical applications in harsh environments.

Aerophilic Co-Embedded N-Doped Carbon Nanotube Arrays as Highly Efficient Cathodes for Aluminum-Air Batteries.

Recently, aluminum-air batteries have attracted great interest owing to their high output energy density, low cost, and feasibility to store and transport Al metal. However, the commercial application is still hindered by the lack of a high-performance air cathode, where the oxygen reduction reaction (ORR) happens, requiring fast charge transfer and mass transport at the catalyst-electrolyte-air interface. Herein, we report an aerophilic air cathode featuring both high intrinsic catalytic activity and large three-phase interface to facilitate air transport, which is prepared by growing cobalt-embedded and nitrogen-doped carbon nanotube (CoNCNT) arrays on carbon fiber paper and then modifying surface wettability with polytetrafluoroethylene solution. The optimized air electrode during the ORR shows a high onset potential of 0.95 V and fast current increase of 342.96 mA cm-2 V-1, which is comparable to the commercial 20 wt % Pt/C, and has even better stability under the same conditions. Moreover, the aluminum-air battery with the aerophilic air electrode is superior to the battery with a commercial Pt/C electrode or aerophobic electrode in terms of maximum power density and long discharging durability. Bubble behavior measurement shows that aerobic wettability plays an important role in gas transport, thus controlling ORR efficiency of the air electrode. The concept of the gas-wettable electrode proves to be effective in the enhancement of oxygen reduction kinetics and would be also adapted in other gas-involved electrodes for energy-related applications.

N-doped carbon nanotube arrays on reduced graphene oxide as multifunctional materials for energy devices and absorption of electromagnetic wave

Considering serious exhausted non-renewable energy resources and electromagnetic radiation pollution issues, it is quite urgent to exploit multifunctional material for realizing both the conversion sustainable energy sources and protection of electromagnetic radiation pollution. Herein, we develop a facile and high-yield preparation route to fabricate a multifunctional material consisted of CoFe alloy nanoparticles encapsulated in nitrogen doped carbon nanotubes arrays grown on both sides of reduced graphene oxide (CoFe@N-CNT/rGO). CoFe@N-CNT/rGO displays excellent properties in the field of rechargeable Zn-air battery and electromagnetic wave absorption. CoFe@N-CNT/rGO shows bifunctional electrocatalytic performances toward oxygen reduction reaction and oxygen evolution reaction, favorably comparable to that of commercial catalysts (Pt/C and IrO2). Furthermore, the assembled liquid and all-solid-state rechargeable Zn-air batteries with CoFe@N-CNT/rGO as air cathode display good charging–discharging performance. As electromagnetic wave absorbing material, CoFe@N-CNT/rGO shows the minimal reflection loss of −33.2 dB at 13.3 GHz, superior to reported carbon-based electromagnetic wave absorbing materials. Based on excellent electromagnetic absorption performance, electromagnetic energy conversion device is designed to realize reasonable utilization and conversion of the absorbed electromagnetic energy. These encouraging results lay a solid foundation for development the multifunctional material and provide an effective strategy for simultaneously solving energy crisis and electromagnetic radiation problems.

Tailoring the d-band center of N-doped carbon nanotube arrays with Co4N nanoparticles and single-atom Co for a superior hydrogen evolution reaction

A 3D self-supported integrated electrode, consisting of heteroatomic nitrogen-doped carbon nanotube arrays on carbon cloth with confined ultrafine Co4N nanoparticles and a distribution of anchored single-atom Co, is fabricated via a cobalt-catalyzed growth strategy using dicyandiamide as the nitrogen and carbon source and a layered cobalt hydroxide-nitrate salt as the precursor. The abundance of exposed active sites, namely, the Co4N nanoparticles, single-atom Co, and heteroatomic N-doped carbon nanotubes, and multiple synergistic effects among these components provide suitable tailoring of the d-band center for facilitating vectorial electron transfer and efficient electrocatalysis. Benefiting from the merits of its structural features and electronic configuration, the prepared electrode exhibits robust performance toward the hydrogen evolution reaction with overpotentials of only 78 and 86 mV at 10 mA cm−2 in acidic and basic electrolytes, respectively. Density functional theory calculations and X-ray photoelectron spectroscopy valence band measurements reveal that the effective tailoring of the d-band center by Co4N nanoparticles plays a crucial role in optimizing the hydrogen adsorption free energy to a more thermoneutral value for efficient electrocatalysis.

High lithiophilic nitrogen-doped carbon nanotube arrays prepared by in-situ catalyze for lithium metal anode

Lithium metal has a very outstanding theoretical capacity (3860 mAh/g) and is one of the most superior anode materials for high energy density batteries. However, the uncontrollable dendrite growth and the formation of “dead lithium” are the important hidden dangers of short cycle life and low safety. However, the uncontrollable dendrite growth and the formation of dead lithium leads to short cycle life and hidden danger, which hinder its practical application. Controlling the nucleation and growth process of lithium is an effective strategy to inhibit lithium dendrite. Herein, a simple in situ self-catalytic method is used to construct nitrogen doped carbon nanotube arrays on stainless steel mesh (N-CNT@SS) as a lithium composite anode. The N-doped CNTs provide a great number of N-functional groups, which enhance the lithiophilic of anode and provide a large number of uniform nucleation sites, hence it has excellent structural stability for cycles. The arrays provide neat lithium-ion transport channels to uniform lithium-ion flux and inhibits dendrite generation, revealed by the COMSOL multi-physics concentration field simulation. The N-CNT@SS composite anode sustain stable at 98.9% over 300 cycles at 1 mA/cm2. N-CNT@SS as the anode is coupled LiFePO4 (LFP) as the cathode construct a full battery, demonstrating excellent cycling stability with a capacity of 152.33 mAh/g and capacity retaining ratio of 95.4% after 100 cycles at 0.5 C.

Fabrication of vertically aligned N-doped carbon nanotube arrays on vermiculite by horizonal chemical vapor deposition

Efficient synthesis of large-scale vertically aligned nitrogen-doped carbon nanotube arrays (VA-NCNTs) has always been a challenge. In this study, we proposed a facile way to obtain mass VA-NCNTs between vermiculite layers by horizonal chemical vapor deposition (CVD). Vermiculite with layered compound as the catalyst substrate, Fe and Mo as the active metal phase is evenly distributed between the vermiculite layers, melamine is pyrolyzed as a single source for both carbon and nitrogen to synthesize nitrogen-doped carbon nanotube (CNT) array materials with relatively uniform length and diameter at an optimum temperature of 800 °C. We explored the effect of temperature on synthesis of VA-NCNTs, the results indicated that the VA-NCNTs are sensitive to temperature changes during the CVD synthesis process, the arrangement, diameter, nitrogen content, and the type of nitrogen function of CNTs could be modified. This work contributes to the study of how the growth temperature affecting the morphology of the as-prepared CNTs, and provides a potential method for the controllable mass production of oriented NCNTs.

Trimetal-based N-doped carbon nanotubes arrays on Ni foams as self-supported electrodes for hydrogen/oxygen evolution reactions and water splitting

Rational design of non-noble metal-based bifunctional electrocatalysts for hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) is still a challenge in water splitting. Herein, a MOF-on-MOF (MOF = metal-organic framework) strategy is developed to obtain trimetal-based nitrogen-doped carbon nanotubes arrays loaded on nickel foams (denoted as FeNiCo@NC/NF). Benefiting from the superior compositional and structural feature, FeNiCo@NC/NF self-supported electrodes exhibit excellent bifunctional HER and OER activity with a low overpotential of 145 and 245 mV at 10 mA cm−2. When simultaneously used as cathode and anode for water splitting, it only requires 1.61 V to achieve 10 mA cm−2 and even outperforms the benchmark electrode couple of Pt/C||RuO2 at higher current densities. Studies discover that trimetallic FeNiCo nanoparticles can provide more synergetic metal active sites, interconnected N-doped carbon nanotubes arrays can offer more effective electron transports channels, and conductive Ni foam substrate can reduce the internal impedance of the material. Density functional theory (DFT) calculations also demonstrate that FeNiCo@NC/NF electrode possesses a favorable Gibbs free energy of hydrogen adsorption (ΔGH*) value of −0.13 eV, which is benefit for its superior HER activity. Overall, our work reports an efficient self-supported electrode for hydrogen/oxygen evolution reactions and water splitting.

Ni/MoC heteronanoparticles encapsulated within nitrogen-doped carbon nanotube arrays as highly efficient self-supported electrodes for overall water splitting

Electrochemical water splitting is one of the most clean and economical method for the production of hydrogen fuels for sustainable energy sources. In order to acquire large-scale hydrogen production, low-cost and robust bifunctional catalysts are needed to catalyze hydrogen and oxygen evolution reactions (HER and OER). Herein, nitrogen-doped carbon nanotube (NCNT) arrays are successfully constructed on the carbon cloth (CC) as bifunctional catalysts for overall water splitting via a facile strategy. Structural analyses indicate that the Ni and MoC nanoparticles are encapsulated in the NCNTs. Experimental results imply that the synergistic effect between Ni and MoC, high electrical conductivity, and binder-free electrode configuration endow the self-supported electrode to have excellent activities with a current density of 10 mA cm−2, at low overpotentials of 70 and 219 mV for HER and OER, respectively. When applied as two-electrode electrolyzer, the self-supported electrodes only need a cell voltage of 1.535 V at a current density of 10 mA cm−2, superior to the benchmark Pt/C and IrO2 couple. Furthermore, the electrolyzer exhibits remarkable stability even at a current density beyond 100 mA cm−2 over 30 h. This strategy will open a facile method to the expansion of high-efficiency bifunctional electrocatalysts for commercial water splitting.

General Fabrication of 3D Hierarchically Structured Bamboo-like Nitrogen-Doped Carbon Nanotube Arrays on 1D Nitrogen-Doped Carbon Skeletons for Highly Efficient Electromagnetic Wave Energy Attenuation.

Hierarchically three-dimensional (3D) micro-nanostructures have promising applications in multifarious fields. Herein, we report a general strategy, that is, in situ catalysis process, for fabrication of nitrogen-doped carbon nanotube (NCNT) arrays on one-dimensional (1D) nitrogen-doped carbon (NC) skeletons. The NCNT arrays branch out from the 1D NC surfaces, resulting in the formation of hierarchically 3D micro-nanostructures. The strategy is involved in the pyrolysis of M-precursor (M = Fe, Co, and Ni) nanowires with the assistance of dicyandiamide. During the synthesis process, the metal components in the precursors serve as catalysts for growing NCNTs, while dicyandiamide provides carbon and nitrogen sources. With the ongoing reaction, the NCNTs were catalytically grown and branched out from 1D NC skeletons. Through the strategy, three kinds of hierarchically 3D structures with encapsulated Fe/Fe3C, Co, and Ni nanoparticles, respectively, were fabricated successfully. As functional materials for attenuating electromagnetic wave energy, these hierarchically 3D structures exhibit satisfactory performances even at a low matching thickness, exceeding most of the carbon-based materials. Typically, the minimal reflection losses of the 3D structures can reach -10.0 dB even as the matching thickness is in the range of 1.4-2.0 mm. Experimental results demonstrate that the excellent attenuation properties toward electromagnetic wave energy are relative to high conduction loss at a low frequency and high dielectric relaxations at a high frequency as well as better impedance matching with the input impedance of the free space. Our method presented here opens a general way for the development of hierarchically 3D carbon-based micro-nanostructures for their practical applications.

Three-dimensional architectures assembled with branched metal nanoparticle-encapsulated nitrogen-doped carbon nanotube arrays for absorption of electromagnetic wave

Three-dimensional magnetic metal nanoparticle-encapsulated nitrogen-doped carbon nanotube arrays (3D M@NCNTS) are fabricated through a facile method. The unique 3D architectures have abundant defects, various N dopants, numerous interfaces, and void spaces. Benefitting from the advantages above, our designed 3D M@NCNTSs exhibit excellent electromagnetic wave absorption properties including strong attenuation abilities, thin thickness of absorber film, and low filler mass loading, superior to most of reported magnetic metal-based absorbers. Typically, the minimal reflection loss of the optimized 3D architecture is – 49.82 dB at a frequency of 7.92 GHz, and efficient absorption bandwidth is 4 GHz as the thickness of the absorber film is merely 2 mm. Furthermore, we also find that the dielectric losses of the 3D architectures can be tuned by the metal composition. Thus, the controllable electromagnetic wave absorption properties can be achieved. Our strategy here may be extended to synthesize other types of 3D architectures as high-performance electromagnetic wave absorbers.

CoNi nanoparticles encapsulated by nitrogen-doped carbon nanotube arrays on reduced graphene oxide sheets for electromagnetic wave absorption

Because of the unique physicochemical properties of three-dimensional (3D) architecture, it has attracted wide attention in the field of electromagnetic wave absorption. However, it is difficult to grow carbon nanotube (CNT) arrays on reduced graphene oxide (rGO) sheets due to ultrathin feature of rGO sheets. In this work, we grow CoNi nanoparticle-encapsulated within nitrogen-doped CNT (NCNT) arrays on ultrathin rGO sheets (3D CoNi/N-GCT) through a simple vacuum freeze-drying process and subsequent carbonization at a high temperature. The unique 3D architectures have large surfaces, abundant defects, various interfaces and void spaces, and nitrogen dopants. Benefitting from these advantages, the 3D CoNi/N-GCT shows excellent absorption properties toward electromagnetic wave. We find that the dielectric loss of our designed sample can be modulated by the metal composition and the morphology, leading to the controllable electromagnetic wave absorption property of the 3D CoNi/N-GCT. Our strategy opens a novel strategy for development 3D architectures for electromagnetic wave absorption.

An Integrated Structural Air Electrode Based on Parallel Porous Nitrogen-Doped Carbon Nanotube Arrays for Rechargeable Li-Air Batteries.

The poor discharge and charge capacities, and the cycle performance of current Li–air batteries represent critical obstacles to their practical application. The fabrication of an integrated structural air electrode with stable parallel micropore channels and excellent electrocatalytic activity is an efficient strategy for solving these problems. Herein, a novel approach involving the synthesis of nitrogen-doped carbon nanotube (N-CNT) arrays on a carbon paper substrate with a conductive carbon-black layer for use as the air electrode is presented. This design achieves faster oxygen, lithium ion, and electron transfer, which allows higher oxygen reduction/evolution reaction activities. As a result, the N-CNT arrays (N/C = 1:20) deliver distinctly higher discharge and charge capacities, 2203 and 186 mAh g−1, than those of active carbons with capacities of 497 and 71 mAh g−1 at 0.05 mA cm−2, respectively. A theoretical analysis of the experimental results shows that the parallel micropore channels of the air electrode decrease oxygen diffusion resistance and lithium ion transfer resistance, enhancing the discharge and charge capacities and cycle performance of Li–air batteries. Additionally, the N-CNT arrays with a high pyridinic nitrogen content can decompose the lithium peroxide product and recover the electrode morphology, thereby further improving the discharge–charge performance of Li–air batteries.

Large-Scale Synthesis of Three-Dimensional Reduced Graphene Oxide/Nitrogen-Doped Carbon Nanotube Heteronanostructures as Highly Efficient Electromagnetic Wave Absorbing Materials.

Herein, we use reduced graphene oxide as a substrate and NiFe as a catalyst to fabricate three-dimensional (3D) nitrogen-doped carbon nanotube (NCNT)/reduced graphene oxide heteronanostructures (3D NiFe/N-GCTs). The 3D NiFe/N-GCTs are composed of two-dimensional (2D) reduced graphene oxide-supported one-dimensional (1D) NiFe nanoparticle-encapsulated NCNT arrays. The NCNTs exhibit bamboo-like shapes with the length and diameter of 3-10 μm and 15-45 nm, respectively. Besides integration of advantages of 1D and 2D nanomaterials, the 3D NiFe/N-GCT heteronanostructure possesses interconnected network structures, sufficient interfaces, numerous defects, hundreds of void spaces enclosed by bamboo joints and the walls of the NCNT in an individual carbon nanotube, and large surface areas, which can improve their dielectric losses toward electromagnetic wave. Thus, the 3D NiFe/N-GCTs show satisfied property toward electromagnetic wave absorption. Typically, the optimized 3D NiFe/N-GCT displays excellent minimal reflection loss (-40.3 dB) and outstanding efficient absorption bandwidth (4.5 GHz), outperforming most of the reported absorbers. Remarkably, the synthesis of 3D NiFe/N-GCTs only involves vacuum freeze-drying and subsequent thermal treatment process at a high temperature, and thus, the large-scale production of 3D NiFe/N-GCTs can be achieved in each batch, affording the possibility of the practical applications of the 3D NiFe/N-GCTs.

Phosphorus and Iron Doped-Porous Carbon As an Efficient Electrocatalyst for Oxygen Reduction Reaction in Alkaline Medium

The U.S. Energy Information Administration has projected a 27% growth in energy consumption by the year 2050.1 The continuous increase in the energy demands worldwide and the environmental concerns reaching critical levels, has required researchers to make the development of clean and sustainable energy conversion devices their paramount challenge. Fuel cells and metal-air batteries with high efficiency and low cost are the prime candidates. Platinum loaded carbon substrate is the catalyst of choice in fuel cells for anodic oxidation of H2 and cathodic reduction of O2 but large-scale commercial production is restricted by its prohibitive cost, limited supply, and weak durability.2 Platinum’s vulnerability to potential drift over time and easy loss of activity through methanol poisoning, questions its competitive catalytic activity. Electrocatalyst that are easily synthesized, have low cost and are earth-abundant is still highly desired. Heteroatom doped carbon electrocatalysts are highly considered candidates and are well researched because of their high abundance and low cost, with transition metal and nitrogen doped carbon material showing competitive result towards the oxygen reduction reaction (ORR).3 , 4 Among those heteroatoms phosphorus doped carbon is an emerging catalyst with high potential. The attraction towards phosphorus arises from the fact that it has a larger atomic radius- hence larger covalent radius- and higher electron-donating ability than nitrogen, making it a promising dopant with an ability to modify the electron transport properties. The Introduction of phosphorus, an atom with lower electronegativity, changes the charge density distribution and electronic properties of a high surface area carbon structure. Phosphorus doping increases the affinity towards an acceptor molecule such as oxygen5, hence a better interaction with the oxygen intermediate and enhances their electrocatalytic activities towards ORR. Such heteroatoms are typically covalently bonded within a carbon framework ensuring long-term stability. The advantages of a heteroatom doped porous carbon are twofold, stabilization of the non-precious metal in the alkaline medium and generation of active sites for facilitating the oxygen reduction reaction. Electrocatalytic activity of phosphorus doped and iron treated phosphorus doped carbon has only been covered by few groups and needs more improvements.6,7 The purpose of the study of electron transfer processes is to understand the reactivity of a relatively new, doped porous carbon complexes incorporating phosphorus as a heteroatom bonded to a metal center. According to DFT calculations, O2 and other ORR intermediates can be stably adsorbed on to Fe sites8, making phosphorus and iron doped carbon a prime candidate for ORR. Using a single precursor as a source of phosphorus, we propose a simple one-step chemical activation, with anhydrous ZnCl2 and anhydrous FeCl2 as the agents of carbonization, yielding P and Fe-doped porous carbon (PFeC). The electrocatalytic activity towards ORR was studied using a rotating ring-disk electrode (RRDE) technique and rotating disk electrode (RDE) connected to the CHI 600 potentiostat. The electrochemical activity of PFeC was compared with the commercially available 20 wt% Pt/C. PFeC showed high activity towards ORR, with comparable onset potential and a small negative shift in half-wave potential. PFeC electrocatalyst selectively catalyzes oxygen to water via a direct four-electron pathway. PFeC showed to be inert toward alcohol oxidation and had superior long-term stability. References (1) U.S. EIA. Annual Energy Outlook 2018 with Projections to 2050. Annu. Energy Outlook 2018 with Proj. to 2050 2018, 44 (8), 1–64. (2) Steele, B. C.; Heinzel, A. Materials for Fuel-Cell Technologies. Nature 2001, 414 (November), 345–352. (3) Lin, L.; Zhu, Q.; Xu, A. W. Noble-Metal-Free Fe-N/C Catalyst for Highly Efficient Oxygen Reduction Reaction under Both Alkaline and Acidic Conditions. J. Am. Chem. Soc. 2014, 136 (31), 11027–11033. (4) Gong, K.; Du, F.; Xia, Z.; Durstock, M.; Dai, L. Nitrogen-Doped Carbon Nanotube Arrays with High Electroctalytic Activity for Oxygen Reduction. Science (80-. ). 2009, 323 (FEBRUARY), 760–764. (5) Cruz-Silva, E.; Lopez-Urias, F.; Munoz-Sandoval, E.; Sumpter, B. G.; Terrones, H.; Charlier, J. C.; Meunier, V.; Terrones, M. Phosphorus and Phosphorus-Nitrogen Doped Carbon Nanotubes for Ultrasensitive and Selective Molecular Detection. Nanoscale 2011, 3 (3), 1008–1013. (6) Razmjooei, F.; Singh, K. P.; Bae, E. J.; Yu, J.-S. A New Class of Electroactive Fe- and P-Functionalized Graphene for Oxygen Reduction. J. Mater. Chem. A 2015, 3 (20), 11031–11039. (7) Singh, K. P.; Bae, E. J.; Yu, J. S. Fe-P: A New Class of Electroactive Catalyst for Oxygen Reduction Reaction. J. Am. Chem. Soc. 2015, 137 (9), 3165–3168. (8) Lee, D. H.; Lee, W. J.; Lee, W. J.; Kim, S. O.; Kim, Y. H. Theory, Synthesis, and Oxygen Reduction Catalysis of Fe-Porphyrin-like Carbon Nanotube. Phys. Rev. Lett. 2011, 106 (17), 8–11.

Cobalt Nanoparticles and Atomic Sites in Nitrogen-Doped Carbon Frameworks for Highly Sensitive Sensing of Hydrogen Peroxide.

In situ monitoring of hydrogen peroxide (H2 O2 ) during its production process is needed. Here, an electrochemical H2 O2 sensor with a wide linear current response range (concentration: 5 × 10-8 to 5 × 10-2 m), a low detection limit (32.4 × 10-9 m), and a high sensitivity (568.47 µA mm-1 cm-2 ) is developed. The electrocatalyst of the sensor consists of cobalt nanoparticles and atomic Co-Nx moieties anchored on nitrogen doped carbon nanotube arrays (Co-N/CNT), which is obtained through the pyrolysis of the sandwich-like urea@ZIF-67 complex. More cobalt nanoparticles and atomic Co-Nx as active sites are exposed during pyrolysis, contributing to higher electrocatalytic activity. Moreover, a portable screen-printed electrode sensor is constructed and demonstrated for rapidly detecting (cost ≈40 s) H2 O2 produced in microbial fuel cells with only 50 µL solution. Both the synthesis strategy and sensor design can be applied to other energy and environmental fields.

One-dimensional nitrogen-doped carbon nanotube arrays fabricated by template carbonization over anodized TiO2 nanotube arrays

Abstract Template carbonization of polypyrrole nanofilm coated on TiO2 nanotube arrays is proposed to fabricate one-dimensional nitrogen-doped carbon nanotube arrays (N-CNTAs) without using any foreign catalyst. Ultra-thin nitrogen-doped carbon nanofilm with thickness of 1 ∼ 2 nm is formed on the wall of TiO2 nanotubes. The N-CNTAs possess high density of graphitic edge planes and exhibit an ideal Nernst behavior towards [Fe(CN)6]3−/4− redox couple. Determination of dopamine has been demonstrated in the linear range of 5–175 μM with a detection limit of 0.19 μM (S/N = 3). Selective monitoring of uric acid with a linear range of 0.1–150 μM in the coexistence of 1 mM ascorbic acid has also been illustrated.

Phosphorus and Iron Doped-Porous Carbon As an Efficient Electrocatalyst for Oxygen Reduction Reaction in Alkaline Medium

The U.S. Energy Information Administration has projected a 27% growth in energy consumption by the year 2050.1 The continuous increase in the energy demands worldwide and the environmental concerns reaching critical levels, has required researchers to make the development of clean and sustainable energy conversion devices their paramount challenge. Fuel cells and metal-air batteries with high efficiency and low cost are the prime candidates. Platinum loaded carbon substrate is the catalyst of choice in fuel cells for anodic oxidation of H2 and cathodic reduction of O2 but large-scale commercial production is restricted by its prohibitive cost, limited supply, and weak durability.2 Platinum’s vulnerability to potential drift over time and easy loss of activity over methanol poisoning, questions its competitive catalytic activity in comparison to Pt or Pt-alloy based catalyst and are easily synthesized, have low cost and are earth-abundant is still highly desired. Heteroatom doped carbon electrocatalysts are highly considered and well researched because of their high abundance and low cost, with transition metal and nitrogen doped carbon material showing competitive result towards the oxygen reduction reaction (ORR).3 , 4 Among those heteroatoms phosphorus doped carbon is an emerging catalyst with high potential. The attraction towards phosphorus arises from the fact that it has a larger atomic radius- hence larger covalent radius- and higher electron-donating ability than nitrogen, making it a promising dopant with an ability to modify the electron transport properties. The Introduction of phosphorus, an atom with lower electronegativity, changes the charge distribution and electronic properties of high surface area carbon structure. Phosphorus doping increases the affinity towards an acceptor molecule such as Oxygen5, hence a better interaction with the oxygen intermediate and enhances their electrocatalytic activities towards ORR. Such heteroatoms are typically covalently bonded within a carbon framework ensuring long-term stability. The advantages of a heteroatom doped porous carbon are twofold, stabilization of the non-precious metal in the alkaline medium and generation of active sites for facilitating the oxygen reduction reaction. Electrocatalytic activity of phosphorus doped and Iron treated phosphorus doped carbon has only been covered by few groups and needs more improvements.6,7 The purpose of the study of electron transfer processes is to understand the reactivity of a relatively new, doped porous carbon complexes incorporating the Phosphorus as a heteroatom bonded to a metal center. According to DFT calculations, O2 and other ORR intermediates can be stably adsorbed on to Fe sites8, making phosphorus and iron doped carbon a prime candidate for ORR. Using a single precursor as a source of phosphorus, we propose a simple one-step chemical activation, with anhydrous ZnCl2 and anhydrous FeCl2 as the agents of carbonization, yielding P and Fe-doped porous carbon (PFeC). The electrocatalytic activity towards ORR was studied using a rotating ring-disk electrode (RRDE) technique and rotating disk electrode connected to the CHI 600 potentiostat. The electrochemical activity of PFeC was compared with the commercially available 20 wt% Pt/C. PFeC showed high activity towards ORR, with comparable onset potential and a small negative shift in half-wave potential. PFeC selectively catalyzes oxygen to water via a direct four-electron pathway. PFeC showed to be inert toward alcohol oxidation and had superior long-term stability. References (1) U.S. EIA. Annual Energy Outlook 2018 with Projections to 2050. Annu. Energy Outlook 2018 with Proj. to 2050 2018, 44 (8), 1–64. (2) Steele, B. C.; Heinzel, A. Materials for Fuel-Cell Technologies. Nature 2001, 414 (November), 345–352. (3) Lin, L.; Zhu, Q.; Xu, A. W. Noble-Metal-Free Fe-N/C Catalyst for Highly Efficient Oxygen Reduction Reaction under Both Alkaline and Acidic Conditions. J. Am. Chem. Soc. 2014, 136 (31), 11027–11033. (4) Gong, K.; Du, F.; Xia, Z.; Durstock, M.; Dai, L. Nitrogen-Doped Carbon Nanotube Arrays with High Electroctalytic Activity for Oxygen Reduction. Science (80-. ). 2009, 323 (FEBRUARY), 760–764. (5) Cruz-Silva, E.; Lopez-Urias, F.; Munoz-Sandoval, E.; Sumpter, B. G.; Terrones, H.; Charlier, J. C.; Meunier, V.; Terrones, M. Phosphorus and Phosphorus-Nitrogen Doped Carbon Nanotubes for Ultrasensitive and Selective Molecular Detection. Nanoscale 2011, 3 (3), 1008–1013. (6) Razmjooei, F.; Singh, K. P.; Bae, E. J.; Yu, J.-S. A New Class of Electroactive Fe- and P-Functionalized Graphene for Oxygen Reduction. J. Mater. Chem. A 2015, 3 (20), 11031–11039. (7) Singh, K. P.; Bae, E. J.; Yu, J. S. Fe-P: A New Class of Electroactive Catalyst for Oxygen Reduction Reaction. J. Am. Chem. Soc. 2015, 137 (9), 3165–3168. (8) Lee, D. H.; Lee, W. J.; Lee, W. J.; Kim, S. O.; Kim, Y. H. Theory, Synthesis, and Oxygen Reduction Catalysis of Fe-Porphyrin-like Carbon Nanotube. Phys. Rev. Lett. 2011, 106 (17), 8–11.