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Developing active, stable and phosphate anion resistant catalysts is critical for high-temperature proton exchange membrane fuel cells based on phosphoric acid-doped polybenzimidazole (PA-PBI) membranes. Herein, an iron catalyst with a five-coordinated Fe active center is elaborately designed. The experimental and theoretical studies show that the planar Fe–N4 moiety with an axial O ligand, benefiting from the optimized charge redistribution, weakens phosphate anion adsorption on Fe active centers and simultaneously promotes oxygen molecule dissociation, resulting in excellent phosphate anion tolerance and ORR activity with the half-wave potential remaining at 0.81 V. The axial-ligand promoted Fe–N–C catalyst is assembled for the first time in a PA-PBI fuel cell, delivering a decent performance. This study sheds light on the intrinsic cause for the phosphate anion tolerance of Fe–N–C catalysts at a molecular level, which provides guidance for designing highly active and stable electrocatalysts for PA-PBI fuel cells. [ABSTRACT FROM AUTHOR]

The development of environmentally benign catalysts for highly regioselective hydroxylation of phenol remains an unsolved challenge in both industry and academia because the electrophilic substitution of phenol simultaneously occurs on both ortho- and para-positions. Herein, we report a designed atomically dispersed iron-based heterogeneous catalyst, in which the iron species is coordinated by a functionalized ionic liquid monolayer on carbon nanotubes. The catalyst exhibits an unprecedented level of regioselectivity (>99%) towards the hydroxylation of phenol and displays a much better activity (TOF towards catechol productivity, 1.79 s−1) compared to the homogeneous free ion system (TOF towards catechol productivity, 0.44 s−1). Both experimental and theoretical investigations confirm that the catalytic oxidation with hydroperoxide undergoes a non-radical addition process and substitutes only the ortho-positions of phenol. This finding provides not only a quite active and selective catalyst for industrially very important reactions, but also a promising methodology of designing biomimetic iron-based heterogeneous catalysts at the atomic level. [ABSTRACT FROM AUTHOR]

EMIm+, as a substitute for Li+, can solve the initial problems that accompany lithiation/delithiation processes on an anode. However, the larger size of EMIm+ limits the options when it comes to electrode materials. Herein, a multilayered Ti3C2Tx MXene was electrochemically pre-intercalated with Fe ions to achieve EMIm+ hosting abilities. As a result, a pre-intercalated MXene electrode exhibited enhanced EMIm+ transport and storage capabilities. When integrated with an EMIm+[PF6]− ionic liquid electrolyte, the assembled DIB provides an energy density of 76 W h kg−1 at a power density of 360 W kg−1, and 94.3% of the energy density is retained after 50 cycles. Compared with a pristine example, the Fe pre-intercalated Ti3C2Tx MXene showed a significant increase in electrochemical performance. Employing this approach to optimize layered materials may open up a new route for accurately tuning intercalated materials. [ABSTRACT FROM AUTHOR]

Supported bimetallic PdxCuy catalysts with precisely controlled Pd/Cu ratios were prepared and characterized by combining sample averaged and microscopic techniques. The active-site isolation effect on reactivity and reaction pathway control with different extent of Pd ensembles in acetylene hydrogenation is unravelled systematically. [ABSTRACT FROM AUTHOR]

Here, we report a new strategy for the construction of a peptide nucleic acid–microRNA nanocomplex with dual function to simultaneously suppress oncogenic microRNAs and upregulate tumor-suppressive microRNAs in target cancer cells. [ABSTRACT FROM AUTHOR]

For lithium–sulfur (Li–S) batteries, it is critical to design advanced host materials with high conductivity and strong binding interactions with sulfur species to trap and convert the polysulfides efficiently. Here, we report a novel BN/CNTs hybrid with paragenesis structure, high surface area and O-doping via a one-step co-pyrolysis method. Such paragenesis structure can remarkably lower the contact resistance between non-conducting BN and conductive CNTs, and the O dopant in BN can narrow the bandgap of BN, both imparting the BN/CNTs hybrid a high conductivity of 1884 S m−1. The BN/CNTs hybrid hosted sulfur shows monoclinic phase instead of the generally reported orthorhombic phase, implying a strong interaction between sulfur and the BN/CNTs hybrid. Moreover, the high surface and the O doping enable BN/CNTs hybrid to adsorb polysulfides with a superior capacity due to the polarization of electrons away from the sulfur atoms towards BN/CNTs. Thus, the BN/CNTs–sulfur cathode can deliver high specific capacity (1374 and 1068 mA h g−1 at 0.2C and 1C, respectively), superior cycling stability (a constant coulombic efficiency of ∼99% and a decay rate of 0.045% per cycle along with 500 cycles at 1C) and excellent rate capability (840 mA h g−1 at 4C). Moreover, it exhibits good high-sulfur-loading areal capacity (up to 4.5 mA h cm−2) with stable cell performance. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) for large-scale grid applications are facing great challenges in terms of development of high-performance electrode materials and screening of suitable electrolytes. Herein, a versatile and scalable protocol for synthesizing two-dimensional (2D) holey cobalt sulfide (h-Co4S3) nanosheets is demonstrated for high-rate and long-life SIBs in an ether-based electrolyte of 1.0 M NaCF3SO3 in diglyme. The 2D h-Co4S3 nanosheets are prepared by sulfuration of leaf-like cobalt based metal–organic frameworks (CoMOFs), and subsequent annealing treatment. Benefiting from the nanosheet nature of in-plane nanopores (10–30 nm), ultra-thinness (＜30 nm), crumpled morphology, and micron-scale lateral size that can provide more active sites and enhanced sodiation/desodiation kinetics, the resulting h-Co4S3 nanosheets achieve a high reversible capacity of 571 mA h g−1 at 0.1 A g−1, and long-life cycling stability with a retention of 80% after 400 cycles for SIBs. Furthermore, theoretical simulation reveals the enhanced structural stability of h-Co4S3 nanosheets with a lower binding energy (0.31 eV) of the Co–O bond in the ether-based electrolyte than that in the carbonate-based electrolyte. Notably, the h-Co4S3 anode offers an exceptional rate capacity of 257 mA h g−1 at 12 A g−1, outperforming most reported cobalt sulfide-based anodes. This strategy will pave a new way to rationally construct MOF-derived 2D nanostructures for various energy-related applications. [ABSTRACT FROM AUTHOR]

Surface functionalized and defect enriched carbon nanotubes (oCNTs) by green ozone/H2O treatment can efficiently anchor gold nanoparticles. This Au/oCNT could be stabilized and well dispersed after thermal treatment and showed robust catalytic activity (20.6 mmol gcat−1 h−1) for the oxidative self-coupling of benzylamine to imine in solvent free conditions. [ABSTRACT FROM AUTHOR]

The selective oxidation of hydrocarbons to the corresponding ketones with solvent-free and molecular oxygen as an oxidant is of great importance in academic and industrial fields in view of economy and environment. In this respect, we present the facile synthesis and characterization of excellent catalysts comprising cobalt nanoparticles encapsulated into graphitic nitrogen-doped carbon nanotubes (Co@GCNs) via one-pot pyrolysis of a chelate compound containing citric acid, melamine, and CoCl2·6H2O. The selective oxidation of ethylbenzene under molecular oxygen and solvent-free conditions is employed as a probe reaction to investigate the catalytic performance; the optimized catalyst shows the best conversion (68%) and selectivity for acetophenone (93%). Combination of the catalytic results of the control group and the different characterization methods demonstrates that high catalytic activity is due to the synergistic effect between metallic cobalt and nitrogen-doped carbon nanotubes. Moreover, the catalyst has high catalytic activity for the aerobic and solvent-free oxidation of other arylalkane substrates. The proposed mechanistic study illustrates that the reaction is a free radical reaction progressing through superoxide radical anions (ṖO2−). [ABSTRACT FROM AUTHOR]

We report herein a green and economical strategy for oxidative modification of carbon nanotubes (CNT) by a facile ozone treatment in the presence of solvent vapor (H2O, 30% H2O2 solution and ethanol). This procedure is able to introduce a considerable level of oxygen groups with a dominant population of carboxyl groups at near ambient temperature. The optimization study of the process provides the reaction temperature and time, as well as the source and partial pressure of the vapor, key parameters determining the oxidation efficiency. The process efficiency and sustainability are assessed to compare with conventional oxidative treatment (e.g., nitric acid oxidation). Ozone treatment assisted by water or H2O2/H2O vapor can introduce abundant oxygenated groups on the sidewalls of CNT, and the process with H2O2/H2O vapor can deliver a much higher selectivity towards carboxyl species on the sidewalls of CNT. With the appropriate functionalization temperature (40 °C) and incremental partial pressure of vapor, the surface defect and oxygen content on the CNT could be dramatically increased. The ozone treated CNT can be used for diverse applications such as metal-free catalyst and support; the modified CNT display higher activity for the ring-opening reaction of styrene oxide than HNO3 treated CNT and develop strong interaction for anchoring iron oxide nanoparticles even up to 350 °C. This ozone treatment in the presence of vapor could also be accomplished by using compressed air as the carrier gas, which can be considered an efficient and eco-friendly functionalization process. [ABSTRACT FROM AUTHOR]

Heteroatom-doped nanocarbons are known to behave differently in the oxygen reduction reaction (ORR) in aqueous systems. In the present study, we reveal the dissimilar roles of oxygen and nitrogen sites in nanocarbons and show that the different functions can jointly promote the ORR in cooperation when appropriately combined. The oxygen sites in general could efficiently facilitate both the HO2− generation and the reduction at high overpotential, while the active nitrogen sites could activate the ORR with a lower energy requirement and simultaneously reduce both O2 and HO2− at low overpotential. A further study to integrate the functionalities in a single nanocarbon reveals the oxidation-resistant nature of the active nitrogen functional group, a chemical basis for the reactivity. [ABSTRACT FROM AUTHOR]

Metal–oxygen batteries are thought to be the ultimate energy storage solution due to their high specific energy. We report here on the synthesis of mesoporous boron-doped onion-like carbon (B-OLC) microspheres and their application in rechargeable sodium–oxygen (Na–O2) batteries. Low overpotential, high specific capacity (over 10 200 mA h g−1), enhanced rate capability (∼7500 mA h g−1 at 0.6 mA cm−2) and excellent cyclability (up to 125 cycles) can be achieved by using B-OLC based electrodes in Na–O2 batteries. The critical role of surface chemistry on the morphology and composition of products is studied and the optimum performance of Na–O2 batteries with B-OLC based electrodes is attributed to the synergistic effects arising from the combination of catalytic activity and the uniquely mesoporous carbon nanoarchitecture. This study indicates that mesoporous B-OLC demonstrated intriguing properties and great potential applications as effective metal-free bifunctional catalysts for Na–O2 batteries and encourages the development of heteroatom-doped carbon materials for performance improvement of metal–oxygen batteries. [ABSTRACT FROM AUTHOR]

The structures of PtNix nanoalloy particles were modified through thermal annealing in different atmospheres. The evolution of surface structures was uncovered by advanced transmission electron microscopy, and the structure–function correlation in methanol electro-oxidation was probed. It provided new insights into the design and synthesis of highly efficient electrocatalysts. [ABSTRACT FROM AUTHOR]

Incorporating heteroatoms into onion-like carbon (OLC, average size ∼5 nm) with a fullerene-like structure and investigating its peculiar properties are fascinating challenges. Here, we present straightforward fabrication of doped OLC samples with a high concentration of boron (0.63–4.57 at%) via a high-temperature thermal diffusion method. The highest proportion of substitutional boron of the boron species reaches 29%, which far exceeds most of the reported boron-doped carbon materials. The influence of boron on the fullerene-like layers and electronic properties of OLC is systematically investigated using Raman spectroscopy with different excitation energies (1.58–3.8 eV) and ultraviolet photoelectron spectroscopy (UPS). The as-prepared boron-doped OLC samples exhibit a perfect four-electron process for the oxygen reduction reaction (ORR), which is similar to commercial Pt/C. It is worth noting that the intrinsic relationship between the electronic properties and catalytic performance of doped samples is explored based on experimental studies instead of theoretical calculations. The results indicate that the lower work function, lower valence band edge and higher density of states (DOSs) of doped OLC are crucial to improve the catalytic performance. Our work can provide valuable information on the design of doped metal-free materials and give new evidence for enhanced ORR activity associated with heteroatom doping and electronic properties. [ABSTRACT FROM AUTHOR]

Exploring the potential catalytic applications of boron-doped carbon materials is a fascinating challenge. Here we describe that boron-doped onion-like carbon and carbon nanotubes as metal-free catalysts exhibit excellent catalytic activity and stability in nitroarene reduction under a stoichiometric amount of reductant. [ABSTRACT FROM AUTHOR]

For the first time, we give a fundamental understanding of the effect of borate-modified nanodiamond on propane oxidative dehydrogenation reaction. Upon increasing the loading amount of borate on the carbon surface, the propene selectivity shows a volcanic curve. The adsorption sites of borate at different loading amounts are thoroughly considered. [ABSTRACT FROM AUTHOR]

A new concept of ionic liquid (IL) mono-dispersing catalyst on nanocarbon surface is presented. The liquid mixture of IL and model catalyst (1-octyl-3-methyl imidazolium phosphotungstate, OPW) on carbon nanotube is in a solid state which can be easily characterized and give a fundamental understanding of the interaction between the catalyst and the IL. The condensed IL is found to weaken the W=O bond of a catalyst that favours its interaction with an oxidizing agent that exhibited a reaction rate of 176 times to the performance of a single OPW during the oxidation of dibenzothiophene. Due to the heterogenization of this system, the catalyst can be easily recycled by a simple gravity separation. [ABSTRACT FROM AUTHOR]

Onion-like carbon (OLC) as a promising carbon material has attracted extensive interest in many fields. In this work, we report for the first time the controllable synthesis of nitrogen-doped OLC via nitric acid pretreatment, followed by different temperature calcination treatment under an ammonia atmosphere. The detailed physicochemical properties of the doped OLC samples are investigated by high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis (EA) and electron energy loss spectroscopy (EELS). Moreover, the potential catalytic performance of such doped samples is evidenced by styrene epoxidation reaction, a kind of typical metal-related catalytic reaction. The results indicate that doped OLC samples exhibit more excellent catalytic performance than pristine OLC and some reported metal-related catalysts. The graphitic nitrogen species plays a key role in the catalytic reaction based on some control experiments and a good linear correlation between the content of this species and the activity results. Our work provides valuable information on the design and application of modified carbon materials in catalytic reactions. [ABSTRACT FROM AUTHOR]

A novel Pd/CNT-SiC monolith catalyst has been prepared by a simple two-step approach. The as-synthesized Pd/CNT-SiC monolith afforded high activity and stability for the Suzuki coupling reactions. In particular, it can be easily separated from reaction mixtures, showing its potential application in liquid phase reactions. [ABSTRACT FROM AUTHOR]

Hydroxyl-attached Sn species are highly dispersed on the surface of mesoporous silica (SBA-15) by the grafting of dimethyldichlorostannane followed by calcination to transform the methyl groups into hydroxyl groups (S–Sn–OH). S–Sn–OH has both Lewis and Brønsted acidic sites, resulting in superior catalytic activities in the acetalisation of glycerol. [ABSTRACT FROM AUTHOR]

Nanodiamond can catalyze the decomposition of methane, and its initial rate is linearly dependent on the number of –CH=CH– defective sites. Thermal treatment improves the ordering of surface atoms, resulting in an inferior activity but a more stable performance over a long period of time, and above 1300 °C few-layered graphene can be found. [ABSTRACT FROM AUTHOR]

Monodisperse metal nanoparticles (NPs) with high activity and selectivity are among the most important catalytic materials. However, the intrinsic process to obtain well-dispersed metal NPs with tunable high density (ranging from 1013 to 1016 m−2) and thermal stability is not yet well understood. Herein, the preparation of metal NPs with tunable areal density from layered double hydroxide (LDH) precursors in which the metal cations were pre-dispersed at an atomic scale was explored. Large quantities of mesopores induced by the Kirkendall effect were formed on the as-calcined layered double oxide (LDO) flakes. The O atoms bonded with Fe3+ cations were easy to be extracted at a temperature higher than 750 °C, which greatly increased the mobility of Fe. Consequently, coalescence of the reduced Fe atoms into large NPs enhanced the Kirkendall effect, leading to the formation of monodisperse embedded Fe NPs on the porous LDO flakes. The flake morphology of LDHs was well preserved, and the areal density of Fe NPs on the LDO flakes can be well controlled through adjusting the Fe content in the LDH precursor. With higher Fe loading, larger Fe NPs with higher areal density were available. When the areal density was increased from 0.039 to 0.55, and to 2.1 × 1015 m−2, the Fe NPs embedded on the LDO flakes exhibited good catalytic performance for the growth of entangled carbon nanotubes (CNTs), aligned CNTs, and double helical CNTs, respectively. This work provides not only new insights into the chemical evolution of monodisperse NPs from an atomic metal-dispersed precursor, but also a general route to obtain tunable NPs as heterogeneous catalysts for chemical and material production. [ABSTRACT FROM AUTHOR]

Carbon materials have received an increasing amount of attention due to their low cost, long-term stability, and high electrocatalytic activity in catalyzing the cathodic oxygen reduction reaction (ORR). However, most of the carbon catalysts have exhibited their excellent activity only in alkaline media, which greatly hinders their practical application in polymer electrolyte membrane fuel cells (PEMFCs). In order to break the restriction of alkaline conditions, sulfur and nitrogen doped carbon nanotubes (SN-CNTs) were designed and successfully prepared via annealing of a mixture composed of nitrogen doped carbon nanotubes (N-CNTs) and sulfur. The result showed the as-prepared SN-CNTs have an enhanced ORR activity in both acidic and alkaline media compared with N doped CNTs (N-CNTs). This report also provides a new approach to explore low-cost electrocatalysts for practical fuel cell applications. [ABSTRACT FROM AUTHOR]

Bulk nitrogen doping can efficiently improve the catalytic performance of carbon nanotubes (CNT) in oxidative dehydrogenation of propane (ODH). The graphitic nitrogen plays a determining role in enhancing their activity by speeding up the activation of oxygen and decreasing the overall activation energy of the reaction. [ABSTRACT FROM AUTHOR]

Positively charged bulk Au particles with size of 20–150 nm were formed on amino-modified porous polydivinylbenzene (Au/PN), which showed superior catalytic performance and good recyclability in the aerobic oxidation of styrene. [ABSTRACT FROM AUTHOR]

MXenes, due to their unique geometric structure, rich elemental composition, and intrinsic physicochemical properties, have multi-functional applications. In the field of electrochemical energy storage, MXenes can be used as active components, conductive agents, supports, and catalysts in ion-intercalated batteries, metal-sulfur batteries, and supercapacitors. The electrochemical performance of MXene materials is closely related to their distinctive physical and chemical properties, which depend on their geometry, surface functional groups, and elemental composition. How to regulate MXene materials to optimize electrochemical functions is a key scientific challenge. Herein, we correlated the function of MXene materials with their interlayer structure, surface functional groups, and specific catalytic sites, analyzed the electrochemical function of MXene materials, and showed how to design the electrochemical function of MXene materials based on ion/electron transport. Additionally, this feature article provides an outlook on the opportunities and challenges for MXenes, offering theoretical and technical guidance on using MXene materials in energy storage systems.

The structures of PtNix nanoalloy particles were modified through thermal annealing in different atmospheres. The evolution of surface structures was uncovered by advanced transmission electron microscopy, and the structure-function correlation in methanol electro-oxidation was probed. It provided new insights into the design and synthesis of highly efficient electrocatalysts.

A highly dispersed Ru/OCNT catalyst synthesized through a facile ethylene glycol reduction approach shows more uniform particle size distribution with ∼1.0 nm compared with that prepared through a conventional impregnation method. Moreover, it also has good thermal stability evidenced by an in situ TEM study.

The structure evolution of twinned Ru nanoparticles supported on carbon nanotubes rearranging into Ru single nanocrystals under the microwave irradiation and the exposed surface of Ru single crystals were observed, which provided new insights into synthesis and application of metal nanoparticle catalysts., (This journal is © The Royal Society of Chemistry 2011)