N-doped Carbon Nanotubes Research Articles

Strong dependence of air stability on thickness in n-doped carbon nanotube thermoelectrics

We demonstrate that the observed (in-)stability of n-doped carbon nanotube films in air not only depends on the employed dopant but is also strongly affected by sample-specific factors, such as the film thickness and density. We show this for two typical dopants, polyethylenimine and a potassium crown ether complex, by preparing films of increasing thickness. We argue that reports on dopant stability cannot be properly assessed without knowledge of these sample-specific parameters, which explains some of the conflicting results in the literature.

Efficient Co0.85Se-CNT sulfur cathode derived from strong catalyst-support interactions: Contribution of adsorption-catalysis mechanism to the redox kinetics of polysulfides

The sluggish conversion chemistry and the notorious ‘shuttle effect’ of lithium polysulfides (LiPSs) are hindering the widespread application of lithium-sulfur batteries (LSBs). Herein, N-doped carbon nanotubes arrays anchored with highly dispersed Co0.85Se nanoparticles were in-situ grown on 3D carbon paper substrates (Co0.85Se-CNT@CP) to promote redox kinetic. The derived sulfur cathode (S/Co0.85Se-CNT@CP) exhibited a sufficient chemisorption ability to accelerate the conversion kinetics and showed considerable capability (1210 mAh/g at 0.2C) and impressive cyclic stability (516 mAh/g at 2.0C after 500cycles). Even at a high loading of 6.0 mg cm−2, the assembled batteries performed a high capacity of 500 mAh/g at 2.0C after 500cycles. The exceptional performance is attributed to the following reasons: On the one hand, the highly efficient conductive carbon nanotubes not only offer sufficient accommodation space for sulfur, but also provide physically confinement for polysulfides. On the other hand, the Co0.85Se nanoclusters drove the transformation of more elemental sulfur to Li2S2/Li2S. In addition, the S/Co0.85Se-CNT@CP did not require conventional binders, thus enhanced surface the reaction kinetic and electron transfer. The associated conversion mechanism was studied by ex-situ XPS, and an adsorption-catalytic model was established to elucidate the electrochemical mechanism. This study proposes a feasible strategy to solve the severe LiPSs shuttling and the sluggish conversion kinetics of LSBs.

Hollow Ti3C2Tx MXene sphere-based ZIF-67 derived central radiative cobalt-tipped carbon nanotubes electrocatalysts for ORR and OER

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays a key role in many renewable energy conversion and storage technologies. As the state-of-the-art ORR and OER electrocatalysts, noble-metal-based electrocatalysts suffer from high price, low earth abundance, single functionality, and poor stability. Developing high performance noble-metal-free ORR and OER bifunctional electrocatalysts as alternatives is highly desirable but remains a significant challenge. In this work, we reported a metal-organic-framework-engaged strategy for the fabrication of central radiative cobalt-tipped N-doped carbon nanotube/hollow Ti3C2Tx sphere composites (h-Ti3C2Tx@Co-NCNT), in which ZIF-67 particles were in situ grown on spherical structure composed of Ti3C2Tx nanosheets constructed with hard template PMMA and then were converted to cobalt-tipped N-doped carbon nanotubes through a pyrolysis process. The hollow Ti3C2Tx nanosheets sphere not only served as conductive scaffolds for the growth of Co-NCNT but also balanced the tradeoff between graphitization of carbon and the surface area. Benefiting from the abundant Co-N/C active sites, reasonably high graphitization of carbon and suitable surface areas, the optimized h-Ti3C2Tx@Co-NCNT manifested comparable ORR (half-wave potential of 0.843 V) and OER (overpotential of 323 mV) activities. In addition, the h-Ti3C2Tx@Co-NCNT assembled zinc-air battery exhibits superior performance beyond commercial Pt/C+RuO2. Certificating this strategy can provide great opportunity for its application in renewable conversion and storage technologies.

Short nanotubular Fe-N-C catalysts with curved catalytic sites and contributing regions for oxygen reduction reaction

The substantial advances of non-precious Fe-N-C materials with both high activity and stability to replace platinum-based catalysts for oxygen reduction reaction (ORR) in fuel cells remain a great challenge, since their intrinsic active site design and contributing microstructure exploration are still unclear. Herein, we propose a solid-phase thermal migration strategy to synthesize Fe, N co-doped nanocarbons with a short nanotubular structure, using ferrocene as Fe source and polyaniline (PANI) as N-doped carbon nanotubes (NCNTs) source. In acidic and alkaline environments, the thermally activated Fe-N-C exhibits efficient ORR performance, and half-wave potential is 30 mV higher than a commercial Pt/C (JM, 20 wt% Pt) in alkaline medium and only 100 mV less than the Pt/C in acidic media. Impressively, the catalyst used in zinc-air battery exhibits an outstanding power density of 144.74 mW·cm−2, higher than the one assembled by the Pt/C (125.67 mW·cm−2). Combining experimental and density functional theory (DFT) calculation results, the superior ORR activity should be attributed to the formation of the efficient off-plane Fe-pyridinic-N4 species at end of the nanotubes. More important, these zigzag-type Fe-pyridinic-N4 sites at the end regions serve as the main active sites, leading to a higher ORR activity. This work opens a door to clarify the active catalytic site types and the contributing microregions of the Fe-N-C catalysts, providing ideas for designing non-noble metal catalysts with curved surfaces and rich edge structures.

Hierarchical architecture of ZIF-8@ZIF-67-Derived N-doped carbon nanotube hollow polyhedron supported on 2D Ti3C2Tx nanosheets targeting enhanced lithium-ion capacitors

The matching of long cycle life, high power density, and high energy density has been an inevitable requirement for the development of efficient anode materials for lithium-ion capacitors (LICs). Here, we introduce an N-doped carbon nanotube hollow polyhedron structure (Co3O4-CNT-800) with high specific surface area and active sites, which is anchored with two-dimensional (2D) Ti3C2Tx nanosheets with metallic conductivity and abundant surface functional groups by electrostatic adsorption to form a hierarchical multilevel hollow semi-covered framework structure. Benefiting from the synergistic effect between Co3O4-CNT-800 and Ti3C2Tx, the composites exhibit superior energy storage efficiency and long cycling stability. The Co3O4-CNT-800/Ti3C2Tx electrodes exhibit a high specific capacity of 817C/g at a current density of 0.5 A/g under the three-electrode system, and the capacity retention rate is 91 % after 5000 cycles at a current density of 2 A/g. Additionally, we assembled Co3O4-CNT-800/Ti3C2Tx as the anode and Activated carbon (AC) cathode to form LIC devices, which showed an electrochemical test result of 90.01 % capacitance retention after 8000 cycles at 2 A/g, and the maximum power density of the LIC was 3000 W/kg and the maximum energy density was 121 Wh/kg. This work pioneered the combination of N-doped carbon nanotube hollow polyhedron structure with two-dimensional Ti3C2Tx, which provides an effective strategy for preparing LIC negative electrode materials with high specific capacitance and long cycling stability.

Bamboo-shaped N-doped carbon nanotubes encapsulated with Co nanoparticles for improved microwave absorption properties

High reflection loss and wide absorption bandwidth materials are in great demand to prevent electromagnetic pollution and military applications. The composites prepared by combining different components with good dielectric and magnetic losses are expected to achieve ideal absorbing performance. In this study, a composite of cobalt nanoparticles enveloped in nitrogen-doped bamboo-like carbon nanotubes (Co@N-CNTs) was prepared by one-step annealing the mixture of melamine and cobalt nitrate at 800 °C in a mixed atmosphere of hydrogen and argon. Co nanoparticles derived from the reaction between H2 and cobalt nitrate during the sintering process were used as catalysts to prompt the carbonization of melamine and the formation of the bamboo-shaped N-doped carbon nanotubes, thus forming the composite structure of bamboo-shaped N-doped carbon nanotubes encapsulated with Co nanoparticles. This Co@N-CNTs composite not only had an excellent dielectric loss and magnetic loss but also greatly improved its impedance matching, thus having good electromagnetic wave absorption performance. The coating made from the Co@N-CNTs composite had a maximum reflection loss (RL) of −35.89 dB at only 1.8 mm thickness at 14.1 GHz and possessed an effective absorption bandwidth of up to 4.91 GHz (12.35–17.26 GHz), suggesting it a high-performance and wide-absorption bandwidth composite material.

Copper-cobalt dual-site on N-doped carbon nanotube with dual-promoted synergy for glucose electrochemical detection

Doping specific active sites and accelerating the decisive step of glucose catalysis to construct highly active glucose sensing electrochemical catalysts remains a major challenge for glucose sensing. Herein, we report the detailed design of Cu–Co dual active site N-doped carbon nanotube (CuCo-NCNTs) obtained by electrodeposition modification, programmed warming and calcination for electrochemical glucose detection. In the CuCo-NCNTs material system, Cu serves as the main active site for glucose sensing. Co with good adsorption of hydroxyl groups acts as the site providing hydroxyl groups to provide oxygen source for Cu oxidized glucose sensing. The synergistic effect between the two active sites in the Cu–Co system and the abundant micro-reactive sites exposed by carbon nanotubes greatly ensure the excellent electrocatalytic performance of glucose oxidation reaction. Therefore, CuCo-NCNTs have good electrocatalytic performance with a sensitivity of 0.84 mA mM−1 cm−2 and a detection limit of 1 μM, and also have excellent stability and specificity. DFT calculations elucidate the decisive steps of H-atom removal in the oxidation of glucose by Cu active site N-doped carbon nanotube (Cu-NCNTs) and Co active site N-doped carbon nanotube (CuCo-NCNTs) materials, illustrating the role of oxygen source provided by hydroxyl group adsorption in the electrochemical sensing process of glucose, thus demonstrating that the electrochemical sensing signal of glucose can be effectively enhanced when cobalt species that readily adsorb hydroxyl groups are introduced into the materials.

Self-Catalyzed Synthesis of Length-Controlled One-Dimensional Nickel Oxide@N-Doped Porous Carbon Nanostructures from Metal Ion Modified Nitrogen Heterocycles for Efficient Lithium Storage.

Transition metal oxides with the merits of high theoretical capacities, natural abundance, low cost, and environmental benignity have been regarded as a promising anodic material for lithium ion batteries (LIBs). However, the severe volume expansion upon cycling and poor conductivity limit their cycling stability and rate capability. To address this issue, NiO embedded and N-doped porous carbon nanorods (NiO@NCNR) and nanotubes (NiO@NCNT) are synthesized by the metal-catalyzed graphitization and nitridization of monocrystalline Ni(II)-triazole coordinated framework and Ni(II)/melamine mixture, respectively, and the following oxidation in air. When applied as an anodic material for LIBs, the NiO@NCNR and NiO@NCNT hybrids exhibit a decent capacity of 895/832 mA h g-1 at 100 mA g-1, high rate capability of 484/467 mA h g-1 at 5.0 A g-1, and good long-term cycling stability of 663/634 mA h g-1 at 600th cycle at 1 A g-1, which are much better than those of NiO@carbon black (CB) control sample (701, 214, and 223 mA h g-1). The remarkable electrochemical properties benefit from the advanced nanoarchitecture of NiO@NCNR and NiO@NCNT, which offers a length-controlled one-dimensional porous carbon nanoarchitecture for effective e-/Li+ transport, affords a flexible carbon skeleton for spatial confinement, and forms abundant nanocavities for stress buffering and structure reinforcement during discharge/charging processes. The rational structural design and synthesis may pave a way for exploring advanced metal oxide based anodic materials for next-generation LIBs.

Architecting N-doped Carbon Nanotube-Rich Carbon Nanofibers with Biomimetic Vine-Leaf-Whisker Structure as Robust Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries.

Efficient and durable bifunctional catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are urgently desirable but challenging for rechargeable Zn-air batteries (ZABs), especially flexible wearable ZABs. Inspired by the vine-leaf-whisker structure in nature, we proposed a three-dimensional (3D) hierarchical bifunctional catalyst (denoted as Co-Fe-Zn@N-CNT/CNF) consisting of N-doped carbon nanotubes embedded with abundant CoFe alloy nanoparticles, leaf-shaped N-doped carbon nanoflakes, and porous carbon fibers for rechargeable ZABs. The special biomimetic structure provides a large specific surface area, allowing for high exposure of the active site and ensuring fast mass transport/charge transfer. The close combination of CoFe bimetallic alloys and N-doped carbon nanotubes delivers high electrocatalytic activity, while the coexistence of various active sites such as metal nanoparticles (NPs), metal-Nx, doped N species, and their synergistic interactions endows the catalysts with more active sites. As such, the Co-Fe-Zn@N-CNT/CNF catalyst achieves superior bifunctional catalytic activities for the ORR (a half-wave potential of 0.84 V) and the OER (an overpotential of 326 mV at 10 mA cm-2) in alkaline media, comparable to commercial Pt/C and RuO2. Remarkably, both aqueous and solid-state ZABs assembled with Co-Fe-Zn@N-CNT/CNF catalysts as air electrodes demonstrate excellent charging/discharging performance, high peak power density, and robust long-term cycling stability. More interestingly, the flexible ZAB performs well even under bending conditions, displaying satisfactory device stability and mechanical flexibility. This study presents a new collective morphological-composition-structural engineering strategy for exploiting the efficient bifunctional oxygen electrocatalysts, which is of great significance for high-performance rechargeable ZABs and wearable energy storage devices.

Confined Co@NCNTs as highly efficient catalysts for activating peroxymonosulfate: free radical and non-radical co-catalytic mechanisms.

A series of transition metal (Co, Ni, Fe) nanoparticles were confined in N-doped carbon nanotubes (NCNTs) prepared (Co@NCNTs, Ni@NCNTs, and Fe@NCNTs) by the polymerization method. The structure and composition of catalysts were well characterized. The catalytic activity of catalysts for activating peroxymonosulfate (PMS) was conducted via acid orange 7 (AO7) degradation. Among the catalysts, Co@NCNTs performed the best catalytic activity. Additionally, Co@NCNTs performed good catalytic activity in pH values of 2.39-10.98. Cl- andSO42- played a promotingroles in AO7 degradation.NO3- presented a weak effect on the catalytic performance of Co@NCNTs, while HCO3- and CO32- significantly suppressed the catalytic performance of Co@NCNTs. Both non-radical (1O2 and electron transfer) and free-radical (·OH and SO4·-) pathways were detected in the Co@NCNTs/PMS system. Notably, 1O2 was identified to be the main active specie in this study. The catalytic activity of Co@NCNTs gradually decreased after cycle reuse of Co@NCNTs. Finally, the toxicity of the AO7 degradation solution in the study was evaluated by Chlorella pyrenoidosa.

Noble metal-free FeCoNiMnV high entropy alloy anchored on N-doped carbon nanotubes with prominent activity and durability for oxygen reduction and zinc–air batteries

Efficient and stable oxygen reduction reaction (ORR) catalysts are essential for constructing reliable energy conversion and storage devices. Herein, we prepared noble metal-free FeCoNiMnV high-entropy alloy supported on nitrogen-doped carbon nanotubes (FeCoNiMnV HEA/N-CNTs) by a one-step pyrolysis at 800 °C, as certificated by a set of characterizations. The graphitization degree of the N-CHTs was optimized by tuning the pyrolysis temperature in the control groups. The resultant catalyst greatly enhanced the ORR characteristics in the alkaline media, showing the positive onset potential (Eonset) of 0.99 V and half-wave potential (E1/2) of 0.85 V. More importantly, the above FeCoNiMnV HEA/N-CNTs assembled Zn-air battery exhibited a greater open-circuit voltage (1.482 V), larger power density (185.12 mW cm−2), and outstanding cycle stability (1698 cycles, 566 h). This study provides some valuable insights on developing sustainable ORR catalysts in Zn-air batteries.

O modified N-doped carbon nanotubes enhanced 2e- oxygen reduction reaction via antibonding activation for efficient antibactrial in netural media

Hydrogen peroxide (H2O2), as a green and renewable environmental protection oxidizing agent, is widely used in chemical synthesis, paper bleaching, sterilization and other industries. The production of H2O2 by two-electron oxygen reduction reaction (2e- ORR) is a promising alternative to the industrial anthraquinone process. In this study, oxygen modified nitrogen-doped carbon nanotubes (O-NCNTs-6) catalyst was prepared for the highly selective ORR to convert H2O2 in neutral media. Notably, the H2O2 selectivity of O-NCNTs-6 is up to 90 %, and the H-cell test exhibits a high H2O2 production rate (about 1035 mmol gcat-1h−1) with excellent bactericidal efficiency (>90 %). Density functional theory (DFT) calculations demonstrate that the antibonding orbitals of O2 can acquire electrons from the as-prepared O-NCNTs-6, thereby facilitating activation of the O-O bond and enhancing the feasibility of the 2e- ORR reaction. Experiments and DFT calculations further confirm that in addition to H2O2, reactive oxygen species (ROS) such as OH and ·O2– produced during the catalytic process play an important role in the sterilization process. This work provides an effective strategy for the design of 2e- ORR catalysts and provides a green and potential electrocatalytic antifouling technology for the antibacterial antifouling field.

MOF derived prismatic-like N-doped carbon nanotube in-situ embedded with Fe3O4/Fe3C heterostructure as an anchoring and catalytic center towards polysulfide in Li-S battery

The development of efficient sulfur host to address the severe shutting effect and sluggish reaction kinetics in lithium-sulfur (Li-S) batteries remains a formidable challenge. Herein, a prismatic-like carbon embedded with highly distributed Fe3O4/Fe3C heterostructure (Fe3O4/Fe3C/PNCT) as a multifunctional sulfur host is reported. In this heterostructure, the polar Fe3O4 works as an adsorbent to anchor polysulfide on heterostructure reaction interface, PNCT with 3D network provides fast e- and Li+transfer pathways to participate reaction and Fe3C acts as a promoter to provide high catalytic activity to enhance reaction kinetics. Through the respective advantages of Fe3O4, Fe3C and PNCT, the synergetic anchoring-diffusion-catalytic conversion performance of Fe3O4/Fe3C/PNCT exceeds their individual benefits. Experiment and DFT all confirm that the Fe3O4/Fe3C/PNCT heterostructure can form a synergetic enhancement effect to inhibit shuttling effect and promote the polysulfide reaction kinetics. On basis of these attractive superiorities, the S/Fe3O4/Fe3C/PNCT cathode shows super high initial capacities of 1432 mAh/g at 0.1 C, and 675 mAh/g at 5 C. Especially, under high sulfur loadings of 7 mg cm−2, the high area capacities of 7.6 mAh cm−2 still can be obtained. This strategy of anchoring and promoting polysulfide conversion can provide a new technology for advanced Li-S batteries.

Facile synthesis of Ni anchored on N-doped carbon nanotube as cathodic electronic conductive agent for thermal battery

Carbon series material is currently the most prevalent electronic conductive agent of thermal battery cathode. For practical applications, such materials suffer from issues such as light density and low conductivity, which can cause dust pollution and affect formability of electrode. Herein, nickel dispersed by bamboo-like nitrogen-doped carbon nanotube (Ni/NCNT) is conveniently synthesized by pyrolysis of nickel-dicyandiamide complex. Benefiting unique structure and the existence of metallic nickel, the single cell with Ni/NCNT cathodic electronic conductive agent yields a long discharge lifetime, accompanying with outstanding current carrying capacity. Concurrently, the Ni/NCNT presents a certain attenuating voltage spike capacity, and thus improving discharge stability. This study offers a potential alternative to conventional conductive agent and antipeak agent for thermal battery.

Transition metal nitride/sulfide nanoparticles attached to nitrogen-doped carbon nanotubes synthesized by modified black powder detonation for efficient overall water splitting

To overcome the energy crisis, the rational construction of efficient electrolytic water catalysts is urgently required. Herein, an innovative proposal was presented for the preparation of self-supported electrolytic water catalysts on nickel foam (NF) substrates using modified black powder (BP) detonation method. The transient high temperature of the controlled detonation can obtain a variety of highly active catalytic components. First, carbon nanotubes (CNTs) were immobilized on NF by electroplating nickel to improve the pore utilization and electrical conductivity of NF. The unique hollow channel structure and extensive surface area of CNTs facilitated the attachment of the active catalysts. The introduction of Co metal salt not only controlled the reaction degreed effectively but also served as an effective transition metal source. With sulfur (S) source in BP and the additional nitrogen (N) source, the detonation successfully produced nano Co5.47N and Ni3S2. Nanocrystals Co5.47N and Ni3S2 along with N-doped CNTs, acquired via transient high-temperature reaction, were abound in defects. Consequently, the obtained sample exhibited excellent catalytic activities for both hydrogen evolution and oxygen evolution reactions. A remarkable overall water-splitting was achieved at a voltage of 1.52 V at 10 mA cm−2 in a two-electrode water electrolysis system.

Decorating N-doped carbon-coated cobalt phosphide nanoparticles onto N-doped carbon nanotubes for high-performance supercapacitors and efficient methanol electro-oxidation

Cobalt phosphide (CoP) has become a promising electrode material for supercapacitors and methanol electro-oxidation due to its high electrical conductivity and and multiple oxidation states. However, the insufficient electroactive sites and large volume changes restrict its electrochemical performance. Herein, a novel CoP/carbon nanocomposite electrode material is designed and synthesized by decorating N-doped carbon (NC) coated CoP nanoparticles onto N-doped carbon nanotubes (N-CNTs). N-CNTs serve as support to grow CoP nanoparticles, which effectively reduces the sizes and aggregation of CoP nanoparticles and provides more electroactive sites. Density function theory calculation results confirm that the coating of NC on CoP nanoparticles increases the electrical conductivity of CoP by transferring electrons from NC to CoP. Meanwhile, a built-in electrical field is formed at the CoP/NC interface, resulting in higher electron/ion transfer efficiency as well as easier surface OH– adsorption. Moreover, the flexible NC shell and N-CNTs supports together effectively withstand the mechanical stress and buffer volume changes of CoP during the charge/discharge processes. Therefore, the obtained N-CNTs@CoP@NC nanocomposite electrode demonstrates high specific capacities (1003 and 621C g−1 at 1 and 10 A g−1, respectively) and good cycling performance (91.2 % retention of initial capacity after 10,000 cycles at 5 A g−1). Furthermore, it also shows a current density of up to 281 mA cm−2at a scan rate of 10 mV s−1with 92.4 % retention of initial current density in 1 M KOH with 0.5 M methanol. These results highlight a feasible strategy for improving practical capacities and cyclic stability of CoP-based electrode materials by integrating nanostructured CoP with one/two-dimensional carbon materials.

Cobalt Nitride Nanoparticles Encapsulated in N-Doped Carbon Nanotubes Modified Separator of Li-S Battery Achieving the Synergistic Effect of Restriction-Adsorption-Catalysis of Polysulfides.

Although lithium-sulfur (Li-S) batteries have broad market prospects due to their high theoretical energy density and potential cost-effectiveness, the practical applications still face serious shuttle effects of polysulfides (LiPSs) and slow redox reactions. Therefore, in this paper, cobalt nitride nanoparticles encapsulated in nitrogen-doped carbon nanotube (CoN@NCNT) are prepared as a functional layer for the separator of high-performance Li-S batteries. Carbon nanotubes with large specific surface areas not only promote the transport of ions and electrons but also weaken the migration of LiPSs and confine the dissolution of LiPSs in electrolytes. The lithiophilic heteroatom N adsorbs LiPSs by strong chemical adsorption, and the CoN particles with high catalytic activity greatly improve the kinetics of the conversion between LiPSs and Li2S2/Li2S during the charge-discharge process. Due to these advantages, the battery with CoN@NCNT modified separator has superior rate performance (initial discharge capacity of 834.7 mAh g-1 after activation at 1 C) and excellent cycle performance (capacity remains 729.7 mAh g-1 after 200 cycles at 0.2 C). This work proposes a strategy that can give the separator a strong ability to confinement-adsorption-catalysis of LiPSs in order to provide more possibilities for the development of Li-S batteries.

Nickel Nanoparticles Encapsulated in N-Doped Carbon Nanotubes for Microwave Absorption

Nickel Nanoparticles Encapsulated in N-Doped Carbon Nanotubes for Microwave Absorption

Mechanism insights into salt tolerance strengthened by CoCe encapsulated N-doped CNTs cathode in microbial fuel cell

To address the challenges of bioanode deactivation and instability of cathode catalysts in the treatment of high-salt organic wastewater using microbial fuel cells (MFCs), a series of CoCe catalysts encapsulated within nitrogen-doped carbon nanotubes (CoCe@NCNTs) was synthesized using a one-pot calcination method. Among the synthesized catalysts, CoCe0.5@NCNTs demonstrated outstanding and stable electrochemical performance in a high-salt environment with 600 mM NaCl, achieving a power density of 144.29 mW m−2, which was 2.7 times higher than that of Co@NCNTs. Notably, the characterization of the catalyst revealed that the addition of Ce element enhanced the stability of the Co crystal structure, mitigated Co leaching, and facilitated the retention of a higher valence state of the Co species after the reaction under high salt conditions. Specifically, the Co3+/(Co2+ + Co3+) ratio in CoCe0.5@NCNTs was 2.82 times larger than that of Co@NCNTs, signifying the favorable influence of the mutual electron conversion between the bimetallic Ce and Co on the performance and stability of catalyst in a high-salt environment. Furthermore, the study assessed the removal efficiency of norfloxacin (NOR), NAD+/NADH ratios, and microbial diversity in conjunction with the stability of cathode electrochemical performance, demonstrating the interconnection between cathode and anode. By considering the practical challenges in treating high-salinity wastewater and the principles of bioelectrochemistry, this paper proposes a mechanism for enhancing anode performance through cathode linkage, thereby providing a novel strategy for MFCs to treat high-salinity organic wastewater treatment.

Deep Oxidation of Chlorinated VOCs by Efficient Catalytic Peroxide Activation over Nanoconfined Co@NCNT Catalysts.

The catalytic removal of chlorinated VOCs (CVOCs) in gas-solid reactions usually suffers from chlorine-containing byproduct formation and catalyst deactivation. AOP wet scrubber has recently attracted ever-increasing interest in VOC treatment due to its advantages of high efficiency and no gaseous byproduct emission. Herein, the low-valence Co nanoparticles (NPs) confined in a N-doped carbon nanotube (Co@NCNT) were studied to activate peroxymonosulfate (PMS) for efficient CVOC removal in a wet scrubber. Co@NCNT exhibited unprecedented catalytic activity, recyclability, and low Co ion leakage (0.19 mg L-1) for chlorobenzene degradation in a very wide pH range (3-11). The chlorobenzene removal efficiency was kept stable above 90% over Co@NCNT, much higher than that of nonconfined Co@NCNS (45%). The low-valence Co NPs achieved a continuous electron redox cycling (Co0/Co2+ → Co3+ → Co0/Co2+) and greatly promoted the O-O bond dissociation of PMS with the least energy (0.83 eV) inside the channel of Co@NCNT to form abundant HO• and SO4•-. Thus, the deep oxidation of chlorobenzene was achieved without any biphenyl byproducts from the coupling reaction. This study provided a new avenue for designing novel nanoconfined catalysts with outstanding activity, paving the way for the deep oxidation of CVOC waste gas via AOP wet scrubber.