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Ethylbenzene (EB) oxidation to oxygenated products catalyzed by carbon nanotubes (CNTs) and CNTs with confined cobalt nanoparticles (Co@C/CNTs) are conducted. Co@C/CNTs with enhanced interfacial charge transfer displays a unique activity. A kinetic model with the simplified network is established, in which seven elementary reactions with prominent features of EB oxidation are selected. The main parameters, reaction rate constant (k) and active energy (Ea) are obtained. Co@C/CNTs could speed up most elementary steps and reduce energy barriers, thus improving the overall activity. The homolytic cleavage of peroxide is confirmed to be the rate‐determining step (RDS). The k ratio (1.55) of acetophenone (AcPO)/1‐phenylethyl alcohol (PEA) is found to be close to the experimental result (rAcPO/rPEA, 1.30). The prediction of EB oxidation is simulated, showing that the synthesis of AcPO dominates the reaction route, while the addition of PEA would prohibit the reaction. [ABSTRACT FROM AUTHOR]

Aerobic oxidation of hydrocarbons yielding corresponding oxygenated products is one of the most important chemical processes. In current work, carbon nanotubes supported encapsulated cobalt nanoparticles with carbon layers (Co@C/CNTs) were synthesized and utilized as catalysts in the oxidation of ethylbenzene (EB) in the liquid phase, exhibiting high catalytic performance. The synergistic effect between Co@C and CNTs played the vital role on facilitating the decomposition of peroxides to enhance the overall activity. The inadequate covered Co@C on CNTs surface were considered as catalytic sites. Density functional theory revealed that the exist of Co nanoparticles could improve the interaction between the catalyst and intermediate free radicals, which were significant for EB oxidation. Last but not least, the electron transfer on carbon surface was enhanced by the incorporation of Co@C nanoparticles, which greatly improved the catalytic performance on EB oxidation. This study provides a new insight into the Co‐based catalysts in the aerobic oxidation of hydrocarbons. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have excellent catalytic activity in liquid phase reaction, especially in aerobic oxidation of cumene. In previous work, the conversion of cumene was 41.8% and the selectivity of cumene hydroperoxide was 71.5%, which was catalyzed by CNTs. But a small amount of impurity Zn2+ totally blocked up the aerobic oxidation of cumene that catalyzed by CNTs, which is an unexpected discovery. By analyzing the catalytic mechanism of CNTs, the inhibition effect of Zn2+ is locked on the abstraction of H atom from cumene. The inhibition of Zn2+ is confirmed in two effects by density functional theory calculations. First, due to the strongly coordination of active oxygen species (ROS) by Zn2+, the energy barrier of initial reaction increases to 1.90 eV, which is nearly 4 times higher than that of the only ROS promoted‐process. Second, the interaction of Zn2+ and RO· or ROO· to inhibits the chain propagation reaction of free radicals. This work precisely demonstrates that the inhibition effect of Zn2+ on initial reaction of cumene. The most significant thing is that the effect of metallic heteroatoms is not negligible in organic oxidation reaction. [ABSTRACT FROM AUTHOR]

The electrooxidation of methanol – the anodic reaction of direct methanol fuel cells – suffers from slow kinetics. Here, we report an enhanced current density for a Pt catalyst supported on nitrogen‐doped carbon nanotube (N−CNT) decorated FeP. X‐ray photoelectron spectra show that the introduction of FeP increases the binding energy of the Pt nanoparticles. The results show that Pt/FeP15%/N−CNT displays a 3.4 times higher forward peak current density compared to commercial Pt/C. The improved performance is attributed to a change in the electronic state of the Pt nanoparticles through the electronic interaction between Pt and FeP, evidenced by the mitigated CO poisoning. [ABSTRACT FROM AUTHOR]

Selective aerobic oxidation of hydrocarbons undergoes a free‐radical chain reaction to yield corresponding value‐added products is the significant process in the chemical industry. Nanocarbons with heteroatoms doping as free‐metal catalysts have been proved to be excellent alternatives in various fields of reactions. In this work, nitrogen doped carbon nanotubes (NCNTs) were applied for the aerobic oxidation of ethylbenzene (EB) in the liquid‐phase. The catalytic performance was unexpectedly suppressed, even lower than the control experiment, which is totally different from earlier publications. Mechanistic studies demonstrated that N doping would inhibit the abstraction of α‐H from EB molecule and end the radical propagation, thus suppressing the overall activity. Addition of TBHP would be helpful for the α‐H abstraction and forming alkyl radicals, which start the Franck‐Rabinowitch cage reaction and promote radical propagation in the presence of carbon catalysts. Herein, a higher catalytic efficiency with 46 % EB conversion and 72 % AcPO selectivity were obtained over NCNTs with O2 and TBHP as dual‐oxidants. [ABSTRACT FROM AUTHOR]

Cyclo[18]carbon (C18) as a special molecular allotrope of carbon composed of two‐coordinate carbon atoms has recently been manufactured and characterized by atomic manipulation. Herein, we analyze the electrochemical reduction characteristics of carbon dioxide (CO2) on typical carbon materials (graphene, C60, carbon nanotubes and C18) using density functional calculations. Encouragingly, C18 shows excellent CO2 reduction activity compared to other carbon materials. [ABSTRACT FROM AUTHOR]

The direct methanol fuel cell is a promising energy conversion device because of the utilization of the state-of-the-art platinum (Pt) anode catalyst. In this work, novel Pt/Ni 2 P/CNTs catalysts were prepared by the H 2 reduction method. It was found that the activity and stability of Pt for methanol oxidation reaction (MOR) could be significantly enhanced while using nickel phosphide (Ni 2 P) nanoparticles as co-catalyst. X-ray photoelectron spectroscopy revealed that the existence of Ni 2 P affected the particle size and electronic distribution of Pt obviously. Pt/CNTs catalyst, Pt/Ni 2 P/CNTs catalysts with different Ni 2 P amount were synthesized, among which Pt/6%Ni 2 P/CNTs catalyst exhibited the best MOR activity of 1400 mAmg −1 Pt, which was almost 2.5 times of the commercial Pt/C-JM catalyst. Moreover, compared to other Pt-based catalysts, this novel Pt/Ni 2 P/CNTs catalyst also exhibited higher onset current density and better steady current density. The result of this work may provide positive guidance to the research on high efficiency and stability of Pt-based catalyst for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Effects of specific nitrogen functionality and oxidative functionalization of the surfaces of nitrogen-doped carbon nanotubes (NCNTs) on the interaction between Pt nanoparticles (NPs) and NCNTs have been systematically investigated. Their catalytic consequences were studied using aerobic oxidation of glycerol and electro-oxidation of CO as probing reactions. By transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD), it was revealed that nitrogen dopant obviously enhanced the dispersion of Pt NPs. Strong interaction between Pt and NCNTs was observed. Graphitic nitrogen preferentially interacted with Pt NPs, evidenced by strong electron transfer from graphitic nitrogen as electron donor to metallic Pt NPs. The oxygen-containing groups introduced by H 2 O 2 oxidation of NCNTs may reduce the donor–acceptor interaction due to the electronegativity of oxygen. By changing the nitrogen amount of NCNTs and introducing oxygen groups, the electron enrichment of Pt NPs can be tuned. Superior catalytic activity was achieved over Pt/NCNTs in the oxidation of glycerol and electro-oxidation of CO, compared with conventional carbon nanotubes as support. Moreover, for both aerobic oxidation of glycerol and electro-oxidation of CO, it was observed that the intrinsic activity depended strongly on the electron enrichment of Pt NPs, ascribed to Pt4 f 7/2 (0) binding energy from XPS, suggesting a promising approach to improving catalytic activity by maximizing the interaction between Pt NPs and graphitic nitrogen sites. [ABSTRACT FROM AUTHOR]

Graphical abstract NMCNTs was synthesized though a facile method, displaying a high removal efficiency and stability in the acid solution and then re-utilized as the catalyst in the electrochemical reduction of CO 2 with a good faradic efficiency (over 90% total efficiency and about 50% for the CO production at 0.6 V). Highlights • Nitrogen doped magnetic carbon nanotubes (NMCNTs) were synthesized. • NMCNTs displayed a high efficiency in the Cr(VI) removal. • NMCNTs showed a high stability in the acid solution. • Recycled NMCNTs was an excellent catalyst for electrochemical reduction of CO 2. Abstract Highly efficient and acid-corrosion resistant for carbon adsorbent in hexavalent chromium removal is a significant property in the practical application. In this study, nitrogen doped carbon nanotubes with encapsulated Fe and Fe 3 C were synthesized through a facile pyrolysis procedure using melamine and ferric chloride as precursors, displaying an excellent efficiency and stability for hexavalent chromium removal. High maximum removal capacities with 35.26 and 970.87 mg g−1 were obtained in neutral and acid solutions, respectively, due to the adsorption process, reduction reaction between Fe0 or Fe2+ nanoparticles and Cr(VI) ions. The unexpected high stability in acid solution (pH at 1) after five recycles was observed for the first time, ascribed to N doping and the tubular structure with encapsulated ferric carbide, which could be resistant to the acid corrosion. After a simple treatment, the used adsorbent could be re-utilized as catalysts for the electrochemical reduction of CO 2 with high faradic efficiency (over 90% total efficiency and about 50% for CO production at −0.6 V), demonstrating a promising potential for reutilizing the used carbon adsorbents. [ABSTRACT FROM AUTHOR]

It has been widely documented that the oxygen-containing functionalities, especially carboxyl groups, on carbon surfaces play crucial roles in the catalytic wet air oxidation (CWAO) reactions. Herein, the CWAO of phenol with molecular O 2 as terminal oxidant using cylindrical and herringbone carbon nanotubes (CNTs) underwent different treatments as catalysts were conducted in batch mode. It was uncovered that the catalytic function of carboxyl groups strongly depended on the structure of CNTs. Parallel CNTs ( p -CNTs) with cylindrical graphitic walls displayed the highest catalytic activity after nitric acid oxidation, due to the carboxylated carbon debris (CDs) coating on surfaces. For herringbone CNTs ( h- CNTs), carboxyl groups are mostly linked to its sidewalls, where abundant edge carbons were exposed, providing an enhanced CWAO activity. The positively synergistic effect of carboxyl groups and adjacent edge carbons was responsible for the activation of O 2 , leading to the improved CWAO activity. This study provides a new insight into the structural effect of carbon materials on the CWAO of phenol. [ABSTRACT FROM AUTHOR]

Selective oxidation of hydrocarbons is of great industrial importance. Nanocarbons are recently found highly active for the aerobic oxidation of cumene. In this work, a detailed kinetics study of cumene oxidation catalyzed by carbon nanotubes (CNTs) and nitrogen doped CNTs (NCNTs) was carried out to disclose the crucial influence of N doping in the cumene oxidation. A kinetics model based on the radical reaction mechanism of cumene oxidation was developed, which contained 7 major elementary steps. The kinetics parameters of cumene oxidation upon CNTs and N-doped CNTs (NCNTs) were obtained by the non-linear aggression of the experimental concentration–time data. Mechanistic insights into the effect of N-doping on carbon catalysis were achieved by comparing the kinetics parameters of CNTs and NCNTs. The decomposition of ROOH was found to be the rate-determine step of the cumene oxidation. The nitrogen doping could reduce the activation energy of CHP decomposition, thereby could remarkably accelerate the overall reaction rate of cumene oxidation. The nitrogen doping could also strengthen the interactions between O 2 , RO , RO 2 and the carbon catalysts. Hence, the selectivities to acetophenone and 2-benzyl-2-propanol were improved. This study provides the insight towards the catalytic role of N dopants in the aerobic oxidation of cumene. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbons can effectively stabilize noble metal particles to achieve high catalytic performances. However, the metallic impurities in carbon nanomaterials, e.g. the residual growth catalysts of carbon nanotubes (CNTs), have some unforeseen effects on the catalysis involving nanocarbons. Herein, we demonstrate that the residual growth catalysts of N-doped CNTs (NCNTs) may significantly deactivate Pd catalysts for the hydrogenation of nitrobenzene. Through high-resolution transmission electron microscopy and CO-stripping, it was determined that the N dopants improved the dispersion of Pd nanoparticles. However, the iron, at ppm level, in residual catalysts encapsulated inside NCNTs can transfer onto the surface of Pd to block active sites so that the activity of Pd/NCNTs was much lower than that of Pd/CNTs. The similar effect was observed for most of the common metallic impurities in carbon materials, including Co, Ni, Mn, Cr, Cu, Zn, Mo, Al and Mg. To exploit the N-doped carbons, we deposited N-doped carbon layers on purified CNTs through pyridine pyrolysis and then supported Pd nanoparticles. By this means, the activity of Pd for nitrobenzene hydrogenation was improved by 3.85 folds compared to conventional CNTs, emphasizing the importance of controlling impurities in N-doped carbon materials for high performance catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile method was established to evaluate the ET reaction rate. • Quantification of ET on d -CNTs is achieved. • Surface defects on d -CNTs are beneficial for the ET reaction rate. • ET ability of d -CNTs on MSI is revealed in the electrooxidation of glycerol. It is still an ongoing challenge to quantitatively determine the number of transferred electrons from carbon supports to metallic catalysts, which is highly related to their catalytic performance. In this work, a facile method combining electrochemical and spectroscopic technologies was proposed to evaluate the electron transfer (ET) reaction rate on carbon nanotubes (CNTs) with defects. Using 7,7,8,8-tetracyanoquinonedimethane (TCNQ) as an electron-accepting molecule, the transferred electrons from CNTs were quantitatively determined through the Beer-Lambert law and coulometric analysis. It was revealed that the edge defects on CNTs are beneficial for the ET reaction rate, due to the lower local work function. Hence, the defective CNTs supported Pt nanoparticles (Pt/ d -CNTs) performed the higher activity in the electrooxidation of glycerol, suggesting the influence of the ET ability of d -CNTs on the electronic metal-support interaction. This scenario is supported by density function theory calculation and X-ray photoelectron spectroscopy. Our results pave a new way to the facile evaluation of electronic metal–carbon interaction. [ABSTRACT FROM AUTHOR]

The influence of catalyst synthesis strategy, including ethylene glycol (EG) reduction, sodium borohydride reduction and impregnation-H 2 -reduction, on the metal-support-interaction of Pt on nitrogen-doped carbon nanotubes (Pt/NCNTs) was systematically investigated and summarized. The catalytic performances were explored in the electro-oxidation reactions of glycerol, formic acid and CO, and the hydrolysis of ammonia borane (AB). Through X-ray photoelectron spectroscopy (XPS), density functional theory calculations and CO stripping technique, it was revealed that the synthesis methods drastically affected the electronic property of Pt nanoparticles (NPs). Pt NPs preferentially interacted with graphitic nitrogen in EG reduction method due to the electron donating property of graphitic nitrogen, while preferentially interacted with pyridinic nitrogen and defects in the impregnation-H 2 -reduction method due to the vacancies containing N P favoring the charged metal ion adsorption. The catalytic activity strongly depended on the electronic property of Pt NPs, which can be ascribed by the binding energy of Pt4f 7/2 (0) from XPS. The higher catalytic activity was obtained over electron-enriched Pt NPs for the electro-oxidation reactions. On the other hand, electron-deficient Pt NPs had better intrinsic activity in AB hydrolysis. The results herein suggested that appropriate synthesis method should be rationally applied to maximize the activities of Pt for targeting reactions benefited from electron-enriched or electron-deficient metal NPs. [ABSTRACT FROM AUTHOR]

A wide spectrum of, up to 22, organic solvents, including aprotic/protic aliphatics/aromatics, was studied to achieve a comprehensive understanding to the solvent effect on the cyclohexene oxidation. It was found that the catalytic activity was significantly influenced by the viscosity, polarity and basicity of solvents in this reaction. Among these solvents, the polar aprotic aliphatic solvents displayed higher catalytic reactivities than other types of solvents. A volcano curve was found describing the dependence of activity on solvent basicity because of the suitable stability of intermediates. Among the solvents investigated, acetonitrile afforded the highest activity and selectivity of 2-cyclohexen-1-one, because of a good compromise between strong polarity and moderate basicity. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have received intensive scientific interests as a metal-free catalyst for the oxidation reactions of hydrocarbons in the liquid phase. However, its application in the liquid reaction is limited by the costly catalyst filtration process. Herein, a structured CNT catalyst was fabricated via growing CNTs on Ni foams with a porous Al 2 O 3 coating layer. The resultant structured CNTs were used both as catalysts and as stirrer in a rotating foam stirrer reactor. The catalytic performance was evaluated in the production of cumene hydroperoxide by the aerobic oxidation of cumene. Under optimized experimental conditions, the cumene conversion reached 25.1%, 14% higher than that of commercial CNTs in a slurry reactor. The excellent adhesion strength of CNTs on the foam and catalytic stability in 5 runs of recycling were demonstrated, opening a new way to employing CNTs as a metal-free catalyst in the liquid phase reactions. [ABSTRACT FROM AUTHOR]

Novel nitrogen doped magnetic carbons (NMC), in-situ synthesized through facile pyrolysis-carbonization processes using Fe(NO 3 ) 3 and melamine as precursors, were demonstrated as excellent nanoadsorbents to remove Cr(VI) effectively. The achieved removal capacity in both neutral and acidic solution was 29.4 and 2001.4 mg g −1 respectively, much higher than the reported adsorbents so far. The unprecedented high adsorption performance can be attributed to the incorporation of the nitrogen dopant, which increased the negative charge density on the surface of adsorbent and thereby enhanced the interaction between the adsorbents and Cr(VI) ions. The density functional theory (DFT) calculation demonstrated that the nitrogen dopants can decrease the adsorption energy between the Cr(VI) ions and NMC (−3.456 kJ mol −1 ), lower than the undoped sample (−3.344 kJ mol −1 ), which boosted the adsorption behavior. Chemical rather than physical adsorption was followed for these magnetic nanoadsorbents as revealed from the pseudo-second-order kinetic study. Furthermore, the NMC showed high stability with recycling tests for the Cr(VI) removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • MnO 2 /CNTs catalysts for cumene oxidation is prepared. • Synergistic effect between MnO 2 and CNTs facilitating CHP decomposition is observed. • Kinetic modelling of 7 elementary steps is established. • MnO 2 /CNTs mainly accelerates the initial and terminal steps. • Enhanced k 80 and reduced E a are obtained over MnO 2 /CNTs. Synergistic effects between the carbon materials and metal oxides usually are considered as the significant factor in the selective oxidation of hydrocarbons. In current study, MnO 2 /CNTs catalysts were prepared under mild condition and applied in the cumene oxidation. As high as 73.44% cumene conversion with 59.06% selectivity of 2-phenyl-2-propanol(PP) was obtained over 21.23-MnO 2 /CNTs, which is much higher than those of CNTs-catalysis and MnO 2 -catalysis systems. The decomposition of cumene hydroperoxide (CHP), a key step for cumene oxidation, was proved to be facilitated by the interaction between MnO 2 nanoparticles and CNTs, which also confirmed from the DFT calculations. These results demonstrated that the synergistic effect between MnO 2 nanoparticles and CNTs would greatly enhance the activity and tune the distribution of products selectivity. The kinetic modeling study in this work further revealed that the interactions between MnO 2 nanoparticles and CNTs would accelerate all the elementary steps, especially, the homolytic cleavage of CHP. The reaction rate constant (k 80 = 9 h−1) for 21.23-MnO 2 /CNTs is 450-folds of CNTs (k 80 = 0.02 h−1). Moreover, the concentration distributions of acetophenone (AP) and PP were well illustrated from the kinetic study. [ABSTRACT FROM AUTHOR]

The group 15 metals, bismuth and antimony, play important roles in promoting noble-metal-catalyzed oxidation reactions toward high value-added chemicals. Herein, we report that the selective oxidation of glycerol to 1,3-dihydroxyacetone (DHA) catalyzed by Pt supported on N-doped carbon nanotubes (Pt/NCNT) can be significantly promoted in the presence of Bi or Sb in reaction solution. This catalyst system showed not only comparable even better performance to the Pt/NCNT with pre-loaded Bi, but also the greatly simplified catalyst preparation. It was found that the Bi-promoted Pt/NCNT underwent dynamic surface reconstruction through leaching and adsorption of Bi adatoms, due to the formation of glyceric acid. By characterizing the adsorption of Bi on Pt catalyst with high-resolution transmission electron microscopy, CO-stripping, horizontal attenuated total reflection infrared spectroscopy and X-ray photoelectron spectroscopy, it has been ascertained that Bi preferentially deposits on the step sites of Pt, and then blocks the terrace sites to promote the Pt catalyst mainly through a geometrical effect, which facilitates the activation and transformation of the secondary hydroxyl group of glycerol through the chelation between substrate and Pt–Bi sites. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) were chemically drilled by supporting cobalt oxide in a controllable way. A series of drilled CNTs with different Co loadings were prepared, characterized and used as the oxygen reduction reaction electrocatalysts. The results show that for the drilled CNTs with the cobalt loading less than 8 wt%, the defects or edge carbons as dominating factor increase the electrocatalytic oxygen reduction reaction (ORR) activity; for the drilled CNTs with the cobalt loading more than 12 wt%, the electron transfer resistance becoming the main determinant decreases the ORR activity. The properly drilled CNTs show dramatically enhanced ORR performance than the original CNTs. [ABSTRACT FROM AUTHOR]

In this study, carbon nanotubes (CNTs) supported Pt-cobalt phosphide (CoP) electrocatalyst (Pt/CoP/CNTs) is designed and prepared for methanol oxidation (MOR) for the first time. The modification of CoP decreases the Pt particle size significantly and increases the electrochemical surface areas due to the interaction between Pt and CoP, which is evidenced by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Among all these catalysts, Pt/4%CoP/CNTs catalyst exhibits the best MOR activity of 1600 mA mg −1 Pt , which is six times that of Pt/CNTs. Moreover, this catalyst also exhibits the higher onset current density and steady current density than the other Pt-based catalysts. The work provides a promising method to develop the highly active and stable Pt-based catalyst for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

To decrease the high cost of cathodic electrocatalysts caused by platinum-based catalysts in fuel cells, a series of silicon-doped carbon nanotubes with different Si contents were synthesized by the thermolysis of trimethylphenylsilane and xylene and used as low-cost metal-free catalysts for the oxygen reduction reaction (ORR). Electrochemical tests showed that the electrocatalytic activities of the synthesized Si-doped carbon nanotubes towards the ORR all were higher than that of pure carbon nanotubes and their ORR activities did not enhance proportionally with the increase of silicon doping content in alkaline medium, indicating a promising potential for designing low-cost and efficient metal-free electrocatalysts in future alkaline fuel cell devices. [ABSTRACT FROM AUTHOR]

Nitrogen doped carbon nanotubes (NCNTs) with encapsulated Fe 3 C nanoparticles (Fe 3 C@NCNTs) are synthesized by a simple direct pyrolysis of melamine and ferric chloride. The characterization results reveal that Fe 3 C is mainly encapsulated in the interior of NCNTs and N species is mainly distributed on the outside surface of NCNTs. Iron and iron carbide catalyze the growth of NCNTs and are wrapped by carbon to form Fe 3 C@NCNTs. The as-prepared Fe 3 C@NCNTs catalyst exhibits superior oxygen reduction reaction (ORR) activity, excellent methanol tolerance and long-term stability in both acid and alkaline media. It is proven that the doped N is the main active site for ORR and the inner Fe 3 C with outside carbon form the synergetic active site to enhance ORR activity. The ORR mechanism of direct four electron transfer pathway is proved in acid and alkaline media. [ABSTRACT FROM AUTHOR]

To design low-cost and efficient cathode electrocatalysts and push forward the commercialization of fuel cells, low platinum content catalyst supported on nitrogen and phosphorus-codoped carbon nanotubes (Pt/NP-CNTs) for the oxygen reduction reaction (ORR) were prepared. Electrochemical tests demonstrated that the Pt/NP-CNTs catalyst exhibited much high ORR activity and remarkable stability in acidic media due to the strong interaction between NP-CNT support and Pt catalyst evidenced by the calculation of the density functional theory, showing a good potential application for a future low-cost proton exchange membrane fuel cell device. [ABSTRACT FROM AUTHOR]

Abstract: The electrocatalytic performances of carbon nanotubes supported platinum (Pt/CNTs) with different Pt loadings for oxygen reduction reaction (ORR) and methanol oxidation (MOR) are studied contrastively. Pt/CNTs showed an opposite change rule along different Pt loadings for ORR and MOR, which is discussed based on the charge transportation and mass transfer. The results show that at low Pt loading, proton conduction is the key factor, which determines the MOR activity; at high Pt loading, mass transfer is crucial, which decides the ORR activity of Pt/CNT catalysts. The viewpoint proposed in this paper can guide the design and preparation of Pt based catalysts for the commercialization of direct methanol fuel cells. [Copyright &y& Elsevier]

Formaldehyde (HCHO) is harmful to environment and human health, even at extremely low concentrations. Catalytic oxidation on metal oxides is an effective method for HCHO removal. Transition metal oxides have attracted much attention due to its advantages of low cost and good redox properties, but it requires the high reaction temperature and energy consumption to reach the good catalytic activity for HCHO removal. In this work, Mn-Co mixed oxides supported on carbon nanotubes (CNTs) were prepared for enhancing the low-temperature catalytic activity of HCHO removal. The results of XRD, TEM and XPS characterization confirmed the formation of CoMn 2 O 4 solid solution on CNTs. The highest relative content of Co3+, Mn3+ and active lattice oxygen were achieved at the optimal composition of 3Mn-1Co. The HCHO oxidation test showed that CoMn 2 O 4 /CNTs (3Mn-1Co) had the best catalytic activity at 160 °C, obtaining 95% HCHO (100 ppm) removal efficiency and 95% CO 2 selectivity at GHSV = 30,000 mL g cat -1 h-1. Compared with the similar catalysts previously reported in literatures, CoMn 2 O 4 /CNTs was of the lower T 90 value for HCHO oxidation. Image 1 • Mn/Co molar ratio of 3:1 was prone to form CoMn 2 O 4 solid solution on CNTs. • The formation of active lattice oxygen on CoMn 2 O 4 was beneficial to HCHO oxidation. • The combination of CNTs and Co-Mn oxides solid solution is promising to prepare catalysts for HCHO removal. [ABSTRACT FROM AUTHOR]

• Surface oxidized nano-cobalt wrapped by N-doped carbon nanotubes (Co@CoO/NC) is prepared. • Co@CoO/NC has a strong adsorption capacity for both some dyes and antibiotics. • The magnetic nano-Co@CoO/NC exhibits excellent stability and reusability. • The main adsorption force is hydrogen bonding and π-π EDA interaction. Dyes and antibiotics in the wastewater discharged by factories have caused immeasurable harm to natural water bodies. It is of great significance to remove the organic pollutants from wastewater. Herein, a novel magnetic nanomaterial of surface oxidized nano-cobalt wrapped by nitrogen-doped carbon nanotubes (Co@CoO/NC) was prepared through a one-step annealing method and used as efficient adsorbing material for tetracycline (TC) and rhodamine B (RhB). The maximum adsorption capacity of the optimal Co@CoO/NC for RhB and TC was 679.56 mg·g−1 and 385.60 mg·g−1, respectively. As a kind of magnetic recyclable and reused adsorbent, Co@CoO/NC could respectively maintain 75% and 84% of absorption capacities for TC and RhB after four repetitions. The adsorption processes were well matched with the pseudo-second-order kinetic model and the Langmuir model. The Zeta potential, XPS, FT-IR and theoretical calculation results showed that the hydrogen bonding and π-π electron donor-acceptor interaction dominated the adsorption of TC and RhB. Due to the presence of CoO on the surface of Co nanoparticles, cation exchange and surface complexation also played an essential role in the adsorption of TC. This work provides a new opportunity for the rational design and construction of efficient, stable and easily recyclable adsorbents in environmental remediation. [ABSTRACT FROM AUTHOR]