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Constructing an ultra‐long‐lived red thermally activated delayed fluorescence carbon dots (TADF‐CDs) with time‐dependent phosphorescence colors (TDPC) in both solid and aqueous is still a challenge. Herein, a red TADF‐CDs, constructed via. a modified solid‐state pyrolysis strategy, show the phosphorescence emissions at 595, 670, and 725 nm with the afterglow lifetime longer than most of reported red TADF‐materials. In addition, the resulting CDs trigger the TDPC activity while the emission colors changed from red to green both in solid state and in aqueous suspension. The synergistic effects of boron‐hybridization in the seed CDs and the additional C═O groups generated in urea‐assisted pyrolysis, result in a stronger spin‐orbit coupling (SOC) between the 1(n, π*) and the 3(π, π*), the mitigated energy gap (ΔEST) and the non‐radiative relaxations of triplet excited states. The TDPC performance endow the resulting TADF‐CDs the usability in advance information security with enhanced‐security‐level encryption strategy. [ABSTRACT FROM AUTHOR]

A key task in today's inorganic synthetic chemistry is to develop effective reactions, routes, and associated techniques aiming to create new functional materials with specifically desired multilevel structures and properties. Herein, we report an ultrathin two‐dimensional layered composite of graphene ribbon and silicate via a simple and scalable one‐pot reaction, which leads to the creation of a novel carbon‐metal‐silicate hybrid family: carbosilicate. The graphene ribbon is in situ formed by unzipping carbon nanotubes, while the ultrathin silicate is in situ obtained from bulk silica or commercial glass; transition metals (Fe or Ni) oxidized by water act as bridging agent, covalently bonding the two structures. The unprecedented structure combines the superior properties of the silicate and the nanocarbon, which triggers some specific novel properties. All processes during synthesis are complementary to each other. The associated synergistic chemistry could stimulate the discovery of a large class of more interesting, functionalized structures and materials. [ABSTRACT FROM AUTHOR]

Knowing the structure of catalytically active species/phases and providing methods for their purposeful generation are two prerequisites for the design of catalysts with desired performance. Herein, we introduce a simple method for precise preparation of supported/bulk catalysts. It utilizes the ability of metal oxides to dissolve and to simultaneously precipitate during their treatment in an aqueous ammonia solution. Applying this method for a conventional VOx−Al2O3 catalyst, the concentration of coordinatively unsaturated Al sites was tuned simply by changing the pH value of the solution. These sites affect the strength of V−O−Al bonds of isolated VOx species and thus the reducibility of the latter. This method is also applicable for controlling the reducibility of bulk catalysts as demonstrated for a CeO2−ZrO2−Al2O3 system. The application potential of the developed catalysts was confirmed in the oxidative dehydrogenation of ethylbenzene to styrene with CO2 and in the non‐oxidative propane dehydrogenation to propene. Our approach is extendable to the preparation of any metal oxide catalysts dissolvable in an ammonia solution. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Strong metal‐support interaction (SMSI) greatly improves the performances of various supported metal nanoparticle catalysts. Classical SMSI relies on the oxide species with substoichiometric oxygen concentration, which prefers to retreat off in humid and oxidative atmospheres. A SMSI is reported with oxygen‐saturated overlayers on Au/TiO2 catalyst achieved by steaming treatment, an opposite condition to the classical SMSI formation. Through a combination of experimental and theoretical methods, this study demonstrates that the strong interactions between the TiOxHy (x≥2) species and Au surface cause the support migration to encapsulate Au nanoparticles. The oxygen‐saturated oxide overlayers are stable in oxidative, reductive, and humid atmospheres, providing great vitality to stabilize metal nanoparticle catalysts under varied and complex reaction conditions to outperform the classical SMSI. [ABSTRACT FROM AUTHOR]

The typical industrial catalyst used for methanol synthesis is a multi‐component catalyst based on Cu/ZnO/Al2O3. The synergies between various phases of this catalyst play a vital role in defining the overall catalytic function and performance. To gain insights into the role and interaction between the relevant components and phases, ex situ and in situ transmission electron microscopy (TEM) was deployed to investigate the structures and phases of an industrial Cu/ZnO/Al2O3 in its precursor, activated and reaction states. High structural inhomogeneity in this material is revealed, i. e. the presence of various phases with different morphologies and compositions. It is shown how structural and compositional changes occur during hydrogen treatment and how compositional inhomogeneity in the starting material translates into differences in the local composition of the activated and working catalyst. The formation of defective metallic copper particles (stacking faults and twins) that are in an intimate contact with zinc oxide (poorly crystalline, partially reduced ZnOx and crystalline ZnO), alumina, Zn−Al oxide and carbon‐zinc‐oxygen containing phases (such as zinc formate) is observed. It is also uncovered that alumina plays a potentially important role in stabilizing cationic zinc species. This work provides atomic‐level insight into the relevant state of an industrial methanol synthesis catalyst and the associated synergistic interplay between the involved phases in reactive atmosphere. [ABSTRACT FROM AUTHOR]

The hetero‐photocatalysts in hollow structure may provide more dispersive reactive sites, the easily accessible open channel for substrates and the intensive visible light harvest ability, which have shown evidently promoting photocatalytic efficiency. Herein, a novel photocatalyst ZIS/Co3S4HLs in hierarchical hollow heterostructure has been constructed by epitaxially growing 2D ZnIn2S4 (ZIS) nanosheets on Co‐ZIF‐L‐derived Co3S4 hollow leaves (Co3S4HLs). The formation of the Schottky junction has promoted the photogenerated charges transfer, which is well proven by the electrochemical analyses and the DFT calculation. It is suggested that both constructed hierarchical hollow heterostructure and the Schottky junction with well‐matched band potentials are responsible for the remarkable H2 evolution rates under the visible light irradiation, which are much higher than most of the reported results by other ZIS‐based composite photocatalysts. The good cyclic photocatalytic activity and structural stability of these hierarchical hollow leaves provide new insight into designing a high‐efficient heterostructure being used in solar energy conversion. [ABSTRACT FROM AUTHOR]

A novel electrochemically assisted cycloaddition process is proposed, in which highly efficient coupling of CO2 with styrene oxide (SO) can be achieved to form styrene carbonate (SC) as a high‐value‐added product. A series of Cu catalysts with different morphologies and chemical states were fabricated on carbon paper (CP) by using in‐situ electrodeposition, and the sample with nano‐dendrimer structure was found to exhibit a relatively high activity of 74.8 % SC yield with 92.7 % SO conversion under gentle reaction conditions, thus showing its potential for practical applications. The relatively high electrochemically active surface area and charge transfer ability of dendrimer‐like Cu benefited the electrochemical reaction. In particular, the Cu2+ species that were formed in situ during the reaction played a vital role in enhancing the activity and selectivity of the proposed Cu/CP hybrid catalyst. Cu2+ atoms served as active sites that can not only electrochemically activate CO2 but also facilitate the ring opening of SO. Mechanistic analysis suggested that the reaction followed electrochemical and liquid‐phase heterogeneous paths, which provide a new green and sustainable route for efficient utilization of CO2 resources for fine chemical electrosynthesis. [ABSTRACT FROM AUTHOR]

Selective hydrogenation of substituted nitroaromatic compounds is an extremely important and challenging reaction. Supported metal catalysts attract much attention in this reaction because the properties of metal nanoparticles (NPs) can be modified by the nature of the support. Herein, the support morphology on the catalytic performance of selective hydrogenation of 3‐nitrostyrene to 3‐vinylaniline was investigated. Pt NPs supported on octadecahedral α‐Fe2O3 supports with a truncated hexagonal bipyramid shape (Pt/α‐Fe2O3‐O) and rod‐shaped α‐Fe2O3 supports (Pt/α‐Fe2O3‐R) were prepared by glycol reduction method. Detailed characterizations reveal that the electronic structure and dispersion of Pt NPs can be modified by the supports. The Pt/α‐Fe2O3‐O catalyst exhibited superior catalytic performance for hydrogenation of 3‐nitrostyrene because of its low coordinated Pt sites and the small Pt NPs size, which is benefit from the high‐index exposed surfaces of truncated hexagonal bipyramid‐shaped α‐Fe2O3 support. The structural evolution during the catalytic reaction was investigated in detail by identical location transmission electron microscopy (IL‐TEM) method, which found that the high cycling activity of Pt/α‐Fe2O3‐O catalyst during the cycle experiment results from the stability of Pt NPs. [ABSTRACT FROM AUTHOR]

In this work, two‐dimensional (2D) Co(OH)2 nanosheets, with large surface areas and wrinkles are obtained, and used to support Pd nanoparticles (NPs) by simple impregnation method as an efficient catalyst for the oxidation of benzyl alcohol under solvent‐free conditions. The resulting 1 wt.% Pd/Co(OH)2 catalyst exhibits a high turnover frequency value of 57999 h−1. The catalysts were characterized by SEM, TEM, AFM, XRD, BET, XPS and CO‐pulse chemisorption. The results of characterizations reveal that the Pd NPs are highly dispersed on the Co(OH)2 nanosheets. The abundant hydroxyl groups on the surface of Co(OH)2 nanosheets promote the reduction of Pd species, resulting in a higher proportion of Pd0 than that of Pd/AC catalyst, which further facilitates the catalytic performances. [ABSTRACT FROM AUTHOR]

Ni‐promoted electrocatalytic biomass reforming has shown promising prospect in enabling high value‐added product synthesis. Here, we developed a novel hybrid catalyst with Ni nanosheet forests anchored on carbon paper. The hybrid catalyst exhibits high efficiency in electrooxidation of HMF to FDCA coupling with H2 production in high purity. The Ni nanosheets have small crystal grain sizes with abundant edges, which is able to deliver an efficient HMF oxidation to FDCA (selectivity >99 %) at low potential of 1.36 VRHE with high stability. The post‐reaction structure analysis reveals the Ni nanosheets would transfer electrons to carbon and readily turn into NiOx and Ni(OH)x during the reaction. DFT results suggest high valence Ni species would facilitate the chemical adsorption (activation) of HMF revealing the reaction pathway. This work emphasizes the importance of the precise control of Ni activity via atomic structure engineering. [ABSTRACT FROM AUTHOR]

Atomically dispersed Fe−N−C electrocatalysts have displayed excellent catalytic performances towards the oxygen reduction reaction (ORR), while the identification of the genuine active sites remains a challenge. Herein, we report a Fe−N−C electrocatalyst of FeSA/HNPC featuring single‐atomic FeN4 sites on hierarchically N‐doped porous carbon (HNPC), which shows a very competitive ORR activity in alkaline solution even at a low electrocatalyst loading of 0.2 mg cm−2 on the working electrode. A comparison of energy barriers in ORR reveals that the single‐atomic FeN4 active sites in FeSA/HNPC existing in the form of pyrrole‐N4−Fe is more favorable than that of pyridine‐N4−Fe for the enhanced ORR activity. Understanding the nature of FeN4 active sites will greatly benefit the design of Fe−N−C electrocatalysts with highly effective ORR performances. [ABSTRACT FROM AUTHOR]

In this paper, a series of highly dispersed CeO2 catalysts on graphene oxide sheets (GO) were prepared by simple impregnation method. The catalysts were applied for selective catalytic reduction(SCR) of NO with NH3. Compared with the 5 wt %CeO2/GO and 15 wt %CeO2/GO catalysts, 10 wt %CeO2/GO catalyst exhibited better catalytic performance in the temperature range of 175–325 °C and higher SO2 resistance at 275 °C. The as‐prepared catalysts were characterized by TEM, AFM, XPS, XRD, BET, H2‐TPR, NH3‐TPD and FT‐IR, respectively. The characterization results indicated that 10 wt %CeO2/GO catalyst possessed larger specific surface area, enriched surface acidic sites, high redox capacity and oxygen vacancies. In addition, Ce3+ on the surface of CeO2/GO catalyst could reduce the oxidation property of SO2, thus improving the SO2 resistance of the catalyst. Meanwhile, the stability of 10 wt %CeO2/GO catalyst was tested. At 275 °C, the NO conversion maintained at 94 % within 30 hours, suggesting the excellent stability. [ABSTRACT FROM AUTHOR]

For supported metal catalysts, metal‐support interactions (MSI) are vital for their catalytic performance, which can be regulated by controlling surface structures of supports. In this work, two kinds of nanodiamond (ND)‐derived carbon materials, i. e. ND@graphene (ND@G) and onion‐like carbon (OLC), were applied to support Ru catalyst. The characterization results show that compared with OLC supported Ru catalyst (Ru/OLC), ND@G supported Ru catalyst (Ru/ND@G) exhibits a higher Ru dispersity, large amount of nanoclusters and Ru single atoms with positive charges dispersing on the surface of ND@G, indicating a stronger MSI in Ru/ND@G. Ru/ND@G favors twin CO adsorbates, while Ru/OLC favors linear adsorbates. For CO oxidation reaction, it was found that Ru/OLC with more metallic Ru NPs exhibited higher catalytic activity compared to Ru/ND@G. Moreover, Ru/OLC showed better reusability and stability compared to Ru/ND@G during CO oxidation reaction. This work highlights the importance of having an adequate rather than an excessively strong MSI for some catalytic systems. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The recent mechanistic understanding of active sites, adsorbed intermediate products, and rate‐determining steps (RDS) of nitrogen (N)‐modified carbon catalysts in electrocatalytic oxygen reduction (ORR) and oxygen evolution reaction (OER) are still rife with controversy because of the inevitable coexistence of diverse N configurations and the technical limitations for the observation of formed intermediates. Herein, seven kinds of aromatic molecules with designated single N species are used as model structures to investigate the explicit role of each common N group in both ORR and OER. Specifically, dynamic evolution of active sites and key adsorbed intermediate products including O2 (ads), superoxide anion O2−*, and OOH* are monitored with in situ spectroscopy. We propose that the formation of *OOH species from O2−* (O2−*+H2O→OOH*+OH−) is a possible RDS during the ORR process, whereas the generation of O2 from OOH* species is the most likely RDS during the OER process. [ABSTRACT FROM AUTHOR]

The article titled "Back Cover: Controlling Metal-Oxide Reducibility for Efficient C-H Bond Activation in Hydrocarbons" discusses the challenge of designing metal oxide catalysts and proposes a method to control their structural properties. The authors, Bingsen Zhang, Evgenii V. Kondratenko, Zhong-Wen Liu, and others, suggest that catalyst post-treatment in an NH3⋅H2O solution can dissolve and precipitate individual catalyst components, allowing for the tailoring of catalyst reducibility. This is important for C-H bond activation in hydrocarbons. The article provides valuable insights for researchers interested in catalyst design and C-H bond activation. [Extracted from the article]

In the article titled "Control of the Reducibility of Metal Oxides for Efficient Activation of C-H Bonds in Hydrocarbons," the authors discuss the challenge of designing metal oxide catalysts. They propose a method of controlling the structural properties of supported/bulk metal oxides through post-treatment in an NH3⋅H2O solution. This treatment allows for the dissolution and simultaneous precipitation of individual catalyst components, resulting in the ability to tailor catalyst reducibility. The authors highlight the importance of catalyst reducibility in the activation of C-H bonds in hydrocarbons. [Extracted from the article]

Deep oxidation/dehydrogenation are longstanding problems for decades in catalytic oxidative dehydrogenation (ODH) of cyclohexane and other alkanes. Here we show a metal‐free catalyst of nanodiamonds (NDs) with unique sp3@sp2 hybrid structure that catalyzes COx‐resistant cyclohexane ODH with remarkable reactivity towards cyclohexene production. The selectivity of cyclohexene can reach as high as 67 % with significantly suppressed COx emission (<5 %), which is on top of the highest reported values among other metal(oxide)/metal‐free catalysts. Structural evolution of sp3@sp2 NDs under annealing treatments and their specific surface functional groups are systematically studied using TEM, XPS, Raman and TPD. By comparing with carbon nanotubes (CNTs), we found that the carbonyl groups stabilized on strained sp3@sp2 core‐shell NDs enhanced the cyclohexene selectivity via preferential cleavage of C−H over C−C bond. Kinetic studies further revealed the underlying reaction pathways that cyclohexane is rapidly dehydrogenated to cyclohexene which subsequently transforms into benzene (fast) and COx (slow). Deep oxidation of both cyclic hydrocarbons is largely suppressed due to the low density of electrophilic functional groups on strongly curved graphitic surface of sp3@sp2 NDs. [ABSTRACT FROM AUTHOR]

Water splitting has been proposed to be a promising approach to producing clean hydrogen fuel. The two half‐reactions of water splitting, that is, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), take place kinetically fast in solutions with completely different pH values. Enabling HER and OER to simultaneously occur under kinetically favorable conditions while using exclusively low‐cost, earth‐abundant electrocatalysts is highly desirable but remains a challenge. Herein, we demonstrate that using a bipolar membrane (BPM) we can accomplish HER in a strongly acidic solution and OER in a strongly basic solution, with bifunctional self‐supported cobalt‐nickel phosphide nanowire electrodes to catalyze both reactions. Such asymmetric acid/alkaline water electrolysis can be achieved at 1.567 V to deliver a current density of 10 mA/cm2 with ca. 100% Faradaic efficiency. Moreover, using an "irregular" BPM with unintentional crossover the voltage needed to afford 10 mA/cm2 can be reduced to 0.847 V, due to the assistance of electrochemical neutralization between acid and alkaline. Furthermore, we show that BPM‐based asymmetric water electrolysis can be accomplished in a circulated single‐cell electrolyzer delivering 10 mA/cm2 at 1.550 V and splitting water very stably for at least 25 hours, and that water electrolysis is enabled by a solar panel operating at 0.908 V (@13 mA/cm2), using an "irregular" BPM. BPM‐based asymmetric water electrolysis is a promising alternative to conventional proton and anion exchange membrane water electrolysis. [ABSTRACT FROM AUTHOR]

Introducing atmosphere in transmission electron microscope enables to directly observe the structural features of catalyst under working conditions. It offers the possibility to study the microstructural evolution and correlate real structures with catalytic properties at nano‐ or atomic‐scale during catalysis. However, the damages to catalyst derived from the high energy electron‐beam irradiation cannot be ignored and may lead to ambiguous conclusions, as the interaction between reactive gas molecules and active structures is only desired. Herein, the α‐Ga2O3 supported Pd catalyst was selected as a model to evaluate the potential effect of electron‐beam on the surface and interface structures, which directly affect the catalytic performance, at varied atmospheres, elevated temperatures and increased electron dose rate in ambient pressure. The results indicate that the supported Pd nanoparticles could be encapsulated by GaOx layer when the imaging electron dose rate is higher than 100 e/Å2s under reduction and oxidizing atmosphere. Either increasing the electron dose rate or elevating the temperature exacerbates the irradiation damage to α‐Ga2O3 support. This work was expected to evaluate the effect of electron dose rate to supported catalysts under chemical environments, and provide guidance for the investigation of in‐situ transmission electron microscopy under ambient pressure. [ABSTRACT FROM AUTHOR]

Metallic platinum nanocatalysts play a key role in the liquid‐phase selective hydrogenation of substrates with more than one unsaturated bond. However, the commonly applied explanation for the effects of different electronic and geometric properties of catalysts on reactions remains of a heuristic nature due to the difficulties involved in preparing catalysts with precise structure. In this work, we have directly loaded pre‐synthesized metallic platinum nanoparticles onto well‐structured ZnO nanorods and then subjected them to thermal treatment in a reductive atmosphere for different temperatures. The effects of the different electronic and geometric properties of the catalysts on the selective reduction of 3‐nitrostyrene to 3‐vinylaniline as a model reaction have been rigorously explored through an analysis of the catalyst structures and the activity and selectivity profiles. Both the electron transfer from zinc to platinum and the decreased platinum surface density as a result of the formation of PtZn intermetallic compounds are key factors for improving the selectivity for the desired 3‐vinylaniline. Azobenzene was detected in the reaction with all the Pt/ZnO catalysts after 10–90 min, which indicates that the reaction follows a condensation mechanism. [ABSTRACT FROM AUTHOR]

Green NH3 production by direct electrocatalytic synthesis from N2 and H2O is still a challenging reaction, which requires us to better understand the nature of the active materials. We show here that iron oxide (Fe2O3) nanoparticles (supported over carbon nanotubes, CNTs) become more active than the corresponding samples after reduction to form Fe‐ or Fe2N‐supported nanoparticles, both indicated as active species in the thermal catalytic reduction of N2 to ammonia. Characterization data, however, indicate that even for these Fe‐ and Fe2N−CNT samples, obtained from Fe2O3−CNT by reduction in H2 or NH3 at 500 °C, the active species responsible for N2 reduction reaction (NRR) at low applied potential (−0.5 V vs RHE) are the same, that is, small (<1–2 nm) iron oxide nanoparticles that are not detected by XRD, but evidenced by XPS and which amount could be correlated to the rate of ammonia formation. This species is stable for at least 24 h of electrocatalytic flow tests. However, at higher applied potentials, sintering/transformation of this species occurs, with loss of the electrocatalytic activity, and Fe2N nanoparticles may also be reduced in situ, forming ammonia, but with irreversible deactivation. [ABSTRACT FROM AUTHOR]

We report mesoporous Co‐Al oxide nanosheets (CoxAl‐Ns, where x denotes the Co/Al ratio in the samples) prepared by calcination of CoAl‐hydrotalcite and subsequent alkaline treatment. X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy measurements show that the prepared Co‐Al oxide nanosheets (CoxAl‐Ns) are very thin (10–15 nm) and exhibit high mesoporosity (3–5 nm). Catalytic CO oxidation tests reveal that the CoxAl‐Ns exhibit excellent catalytic performances at relatively low temperatures: for example, the Co2.5Al‐Ns catalyst could achieve 99% CO conversion at −98°C. Kinetic studies and experimental investigations indicate that the high activity of the Co2.5Al‐Ns sample is strongly related to the abundance of active sites associated with the large Brunauer–Emmett–Teller surface area. The Co2.5Al‐Ns catalyst also achieves full conversion of CO in tests performed with a gas mixture simulating automobile exhaust gas at 200°C. After loading the Co2.5Al‐Ns on a porous ceramic substrate, the obtained Co2.5Al‐Ns/PC shows high activity and stability in CO oxidation process. These features are potentially important for future industrial applications of these catalysts. [ABSTRACT FROM AUTHOR]

Graphene oxides (GOs) are popular catalyst supports for precious metals in nanoparticle form. The hydrogen oxidation reaction (HOR) and the hydrogen evolution reaction (HER) on individual GO platelets decorated with Pd nanoparticles (Pd/GOs) were investigated. The results suggest that the catalytic activity is confined to the zone physically close to the point of electrical contact between platelet and electrode with just a fraction of the platelet active. [ABSTRACT FROM AUTHOR]

Controllable synthesis of well‐defined supported intermetallic catalysts is desirable because of their unique properties in physical chemistry. To accurately pinpoint the evolution of such materials at an atomic‐scale, especially clarification of the initial state under a particular chemical environment, will facilitate rational design and optimal synthesis of such catalysts. The dynamic formation of a ZnO‐supported PdZn catalyst is presented, whereby detailed analyses of in situ transmission electron microscopy, electron energy‐loss spectroscopy, and in situ X‐ray diffraction are combined to form a nanoscale understanding of PdZn phase transitions under realistic catalytic conditions. Remarkably, introduction of atoms (H and Zn in sequence) into the Pd matrix was initially observed. The resultant PdHx is an intermediate phase in the intermetallic formation process. The evolution of PdHx in the PdZn catalyst initializes at the PdHx/ZnO interfaces, and proceeds along the PdHx ⟨111⟩ direction. A palladium catalyst supported on ZnO is monitored in situ and in chemical environments relevant to catalysis. Structural evolution of PdZn intermetallic metal nanoparticles (NPs), visualized at an atomic scale, reveals the evolution of a PdHx intermediary species at the interface between PdHx and the ZnO support. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Transition‐metal oxide/nanocarbon hybrids are known to deliver a cooperative oxygen reduction reaction (ORR) with a synergistic effect of the hybrid interface. This work assesses a series of first‐row transition‐metal oxides in the form of surface‐confined clusters on carbon nanotubes, as a mimic of fully exposed hybrid interfaces, providing an activity benchmark for hybrid catalysts. Among the selected metal oxides, MnOx and CoOx are found to be the most active first‐row transition‐metal oxide clusters for the ORR, given their excellent peroxide‐reducing capability at low overpotential. FeOx and CuOx are also active for the same role, except their peroxide‐reducing activity is only activated with substantial overpotential. Other metal oxides (NiOx and ZnOx) do not appear to show any activity toward the ORR, even with an integrated interface as a source for the possible synergistic effect. [ABSTRACT FROM AUTHOR]

Abstract: The introduction of surface functional groups onto graphene can provide additional pseudocapacitance for supercapacitors. However, the compensation for the loss of electrical conductivity arising from the disruption of the conjugated system remains a big challenge. Here, a novel strategy is reported for the design of oxygen clusters distributed in graphene with “paddy land” structure via a low‐temperature annealing process. Moreover, the distribution, content, and variety of oxygen groups and the conductivity of reduced graphene oxide (RGO) can be easily adjusted by annealing temperature and time. First‐principles calculations demonstrate that “paddy land” structure exhibits conjugated carbon network, ultralow HOMO–LUMO gap, and long span of atomic charge values, which are beneficial for the enhanced pseudocapacitance and rate performance. As a result, the functionalized graphene (GO‐160‐8D) exhibits high specific capacitance of 436 F g−1 at 0.5 A g−1, exceeding the values of previously reported RGO materials, as well as excellent rate performance (261 F g−1 at 50 A g−1) and cycling stability (94% of capacitance retention after 10 000 cycles). The findings may open a door for finely controlling the location and density of functionalities on graphene for applications in energy storage and conversion fields via a green and energy‐efficient process. [ABSTRACT FROM AUTHOR]

Dual-ion batteries are promising devices, owing to their compatibility of high energy density and high power density, provide that the volume expansion of positive graphite and the decomposition of the electrolyte are well addressed. Herein, we report a facile strategy of using low-cost carbon fiber paper for package enhancement of dual-ion batteries. The three-dimensional structure offers both conductivity and structure integrity, while the highly graphitic fiber paper endows the high intercalation potential towards high energy density. High stability results from such integrative electrode structure. Matching with electrical double-layer capacitive graphene and ionic liquids, with a wide electrochemical stability window, a dual-ion battery has been fabricated to achieve a specific energy of 149 Wh/kg at a specific power of 1011 W/kg, and the specific energy retains 85 % after 1000 cycles. This accessible 3D paper electrode provides a new route for an integral electrode construct that can be used in ultrastable, high-efficiency energy-storage devices. [ABSTRACT FROM AUTHOR]

The varied surface structures of a Pd catalyst showed different catalytic performances in the partial hydrogenation of acetylene. The exposed Pd (1 0 0) facet is considered to be the most selective of all other facets for the formation of ethylene, but it is unstable and the fine structure needs to be revealed during the reaction. Herein, the evolution of the surface structure of cubic Pd nanoparticles, which are all bound with (1 0 0) facets, was studied by transmission electron microscopy in the partial hydrogenation of acetylene. Furthermore, the relation between the varying surface structure and the activity/selectivity was correlated. The (1 0 0) facets of Pd were transformed into stepped facets during the reaction, derived by adsorption/desorption of the reactants and energy compensation, which was the main reason for the decrease in the selectivity towards ethylene. [ABSTRACT FROM AUTHOR]

The ultimate objective of chemical conversion is to achieve 100 % selectivity from catalysis, and this is also a prodigious challenge for the conversion of light paraffins into olefins, because it involves controlled activation of highly stable aliphatic C−H bonds. Herein, we show that metal-free boron nitride (BN) nanosheets not only enable the oxidative dehydrogenation of ethane to ethylene exclusively at near 10 % conversion, but they also deliver a remarkable 60 % selectivity at an ethane conversion of 78 % and remain stable over 400 h at 575 °C. Our operando infrared spectroscopy and 18O isotope tracer study explicitly demonstrates that B−O(H) active sites are formed at the edges of BN through the aid of ethane, and the dehydrogenation circle is completed over these B−O sites by the assistance of O2. [ABSTRACT FROM AUTHOR]

Nitrogen-doped sp2 nanocarbon materials have been considered promising catalysts for CO2 electro-reduction. However, a fundamental understanding about product selectivity and the reaction routes is still lacking. In this report, the reaction mechanism on nitrogen-doped sp2 nanocarbon materials is resolved by clarifying the authentic origin of the carbonaceous products: CO and HCO2−. Two carbon-reduction pathways are identified based on a series of comparative studies by using differential electrochemical mass spectrometry and in situ CO adsorption experiments: a dominant pathway leading to CO from CO2 and a secondary pathway leading to HCO2− from HCO3−. Neither hydrocarbon (C xH y) nor alcohol or aldehyde (C xH yO z) were detected in the reduction of CO2. However, CO, which is generally regarded as an intermediate to be transformed into these products on metal catalysts, can undoubtedly be produced and adsorbed on nitrogen-doped sp2 nanocarbon catalysts during the reaction. [ABSTRACT FROM AUTHOR]

The preparation of photocatalysts with high activities under visible-light illumination is challenging. We report the rational design and construction of a zirconium-doped anatase catalyst (S-Zr-TiO2) with Brønsted acidity and photoactivity as an efficient catalyst for the degradation of phenol under visible light. Electron microscopy images demonstrate that the zirconium sites are uniformly distributed on the sub-10 nm anatase crystals. UV-visible spectrometry indicates that the S-Zr-TiO2 is a visible-light-responsive catalyst with narrower band gap than conventional anatase. Pyridine-adsorption infrared and acetone-adsorption 13C NMR spectra confirm the presence of Brønsted acidic sites on the S-Zr-TiO2 sample. Interestingly, the S-Zr-TiO2 catalyst exhibits high catalytic activity in the degradation of phenol under visible-light illumination, owing to a synergistic effect of the Brønsted acidity and photoactivity. Importantly, the S-Zr-TiO2 shows good recyclability. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are functionalized with nitrogen atoms for reduction of carbon dioxide (CO2). The investigation explores the origin of the catalyst′s activity and the role of nitrogen chemical states therein. The catalysts show excellent performances, with about 90 % current efficiency for CO formation and stability over 60 hours. The Tafel analyses and density functional theory calculations suggest that the reduction of CO2 proceeds through an initial rate-determining transfer of one electron to CO2, which leads to the formation of carbon dioxide radical anion (CO2.−). The initial reduction barrier is too high on pristine CNTs, resulting in a very high overpotentials at which the hydrogen evolution reaction dominates over CO2 reduction. The doped nitrogen atoms stabilize the radical anion, thereby lowering the initial reduction barrier and improving the intrinsic activity. The most efficient nitrogen chemical state for this reaction is quaternary nitrogen, followed by pyridinic and pyrrolic nitrogen. [ABSTRACT FROM AUTHOR]

In alkaline medium, it seems that both metal-free and iron-containing carbon-based catalysts, such as nitrogen-doped nanocarbon materials, FeO x-doped carbon, and Fe/N/C catalysts, are active for the oxygen reduction reaction (ORR). However, the order of activity of these different active compositions has not been clearly determined. Herein, we synthesized nitrogen-doped carbon black (NCB), Fe3O4/CB, Fe3O4/NCB, and FeN4/CB. Through the systematic study of the ORR catalytic activity of these four catalysts in alkaline solution, we confirmed the difference in the catalytic activity and catalytic mechanism for nitrogen, iron oxides, and Fe-N complexes, respectively. In metal-free NCB, nitrogen can improve the ORR catalytic activity with a four-electron pathway. Fe3O4/CB catalyst did not exhibit improved activity over that of NCB owing to the poor conductivity and spinel structure of Fe3O4. However, FeN4 coordination compounds as the active sites showed excellent ORR catalytic activity. [ABSTRACT FROM AUTHOR]

The lithium-oxygen (Li-O2) battery is a very appealing candidate for advanced high energy applications owing to its exceptionally high specific energy. However, its poor energy efficiency, rate capability, and cyclability remain key barriers to its practical application. In this work, using a rationally designed cathode based on a bimodal mesoporous nitrogen-doped graphene/carbon nanotube (NGC) composite, we have developed a Li-O2 battery demonstrating enhanced round-trip efficiency (ca. 85 %) and excellent cyclability over 400 cycles under a high current rate of 500 mA g−1. The excellent cyclability and rate capability are attributed to improved stability of the aggressive LiO2 intermediate on the nitrogen-doped carbon surface in addition to the favorable hierarchical architecture of NGC. These results demonstrate a valuable research direction to achieve highly stable and reversible Li-O2 batteries through tuning the surface chemistry of the cathode in addition to finding a stable electrolyte solvent. [ABSTRACT FROM AUTHOR]

The complex (Mo,V)-based multicomponent M1 phase with a characteristic network of pentagonal, hexagonal, and heptagonal channels is the key catalyst for the catalytic oxidation from propane to acrylic acid. Herein, the atomic-scale structural dynamics in the orthorhombic Mo-V-Te-Nb oxide were probed under electron-beam stimulation. The recorded in situ scanning transmission electron microscopy images unravel the strong bonding and correlation between the (Mo,V)O6 octahedra and the central Nb moieties in the pentagonal channels. Such dynamic electron microscopy imaging can pave the way to chemically tailoring structural units of a general catalogue of functional polyoxo meta lates through applying top-down electron-beam probing. [ABSTRACT FROM AUTHOR]

Carbon is a unique and versatile element in nature that can form different architectures. Heteroatom (e.g., B, N, O, P, and S) modification has been proven to be an effective way to tailor the chemical and electrical properties of the carbon surface. Moreover, nanocarbons have been reported to be good supports for metal nanoparticles (NPs). It is essential to study the metal-support interaction between surface-modified carbon and metal NPs to understand performance. Advanced analytical transmission electron microscopy techniques are powerful tools that can be used to probe the metal-carbon support interaction in carbon-supported metal catalysts, as they can directly uncover local structures of the surface and the bulk of catalysts at the atomic scale and can also reveal chemical and electronic structural information that is related to their synthesis and catalytic properties significantly affecting their performance. Herein, several selected examples will be reviewed. [ABSTRACT FROM AUTHOR]

Employing anatase TiO2 nanocrystals with predominantly {0 0 1} facets, anatase TiO2 nanocrystals with predominantly {1 0 0} facets, and TiO2 P25 with predominantly {1 0 1} facets as supports, we have comprehensively studied the morphology effect of TiO2 on the Au-TiO2 interaction, structure, and catalytic performance of Au/TiO2 catalysts in C3H6 epoxidation with H2 and O2, C3H6 oxidation with O2, and H2 oxidation. A strong morphology-dependent interplay between the Au-TiO2 interaction and the catalyst structure was observed. Only Au nanoparticles were present in the Au/TiO2 catalysts and the Auδ− species was the largest in Au/TiO2{0 0 1} due to the creation of surface O vacancies of TiO2{0 0 1} upon Au loading, whereas the fraction of Auδ+ species was largest in Au/TiO2{1 0 0} due to the preserved surface stoichiometry of TiO2{1 0 0} upon Au loading. In H2 oxidation, Au/TiO2{1 0 0} with the largest fraction of Auδ+ species was the most active but least selective toward H2O2, whereas Au/TiO2{0 0 1} with the largest fraction of Auδ− species was the most selective toward H2O2. In C3H6 oxidation with O2, tiny C3H6 conversions with the formation of partial oxidation products were observed at low temperatures, whereas C3H6 combustion occurred at high temperatures. In C3H6 epoxidation with O2 and H2, the ensemble consisting of closely connected Auδ− and Ti4+ on anatase TiO2{0 0 1} and {1 0 1} facets with weak adsorption ability was the active structure and the Au/TiO2{0 0 1} catalyst containing the largest amount of this ensemble was the most active. These results demonstrated morphological engineering of oxides as an effective strategy to optimize the catalytic performance and understand the fundamentals of catalysis involving oxides. [ABSTRACT FROM AUTHOR]

Non-precious metal oxide/carbon hybrid electrocatalysts are of increasing importance for the oxygen reduction reaction (ORR). A synergistic effect is commonly used to explain the superior ORR activity exerted by metal oxide/nanocarbon hybrids, and this effect is attributed to covalently coupled interfaces between the two materials. However, the origin of the high activity, the structure, and the electrocatalytic nature of the interface remain unclear. By combining X-ray photoelectron spectroscopy with synchrotron far-infrared spectroscopy, we resolved the interface structure between spinel manganese oxide nanocrystals and graphene oxide nanoribbons, and the role of this interface in the promoted ORR. Moreover, we demonstrated the excellent ORR activity by a functional synergism of the hybrid constituents through a series of comparative electrochemical experiments. [ABSTRACT FROM AUTHOR]

Nitrogen-doped nanocarbon materials as metal-free electrocatalysts for the oxygen reduction reaction (ORR) have attracted great attention, owing to their catalytic activity close to Pt/C in alkaline media. Annealed nanodiamonds (AND) possess a special structure, because we can finely control the carbon sp2/sp3 ratio. This provides a good opportunity to study the relationship between ORR performance (activity and stability) and the special structure of AND. We have used nitrogen-doped annealed nanodiamonds (NAND) with varied carbon sp2/sp3 ratio as metal-free electrocatalysts for ORR in alkaline media. NAND showed higher catalytic activity for ORR with higher content of sp2 carbon and larger amount of nitrogen species present as pyridinic groups. More importantly, NAND displayed stability superior to other nitrogen-doped nanocarbon materials as a result of transformation of carbon from sp3 to sp2 during electrochemical cycling. [ABSTRACT FROM AUTHOR]

Two kinds of phosphorus-modified onion-like carbons dominated by COP bonds and CP bonds were fabricated and further used as catalysts in the oxygen reduction reaction (ORR). The results show that the bonding state of phosphorus has a significant effect on the ORR catalytic activity. The formation of COP bonds improves ORR activity, whereas CP bonds play an adverse role in stabilizing the key intermediates during the ORR owing to the distorted graphitic structure, as confirmed by the work function value. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a decisive role for the efficiency of fuel cells and metal-air batteries. The nitrogen doped carbon materials with low cost and long durability are potential catalysts to replace precious metal catalyst for oxygen electrochemistry; however, the unexposed active sites induced by the bulk dopant atoms are hardly accessible and consequently scarcely contribute to the catalytic property. In this study, carbon nanotubes (CNTs) are selected as the platform to demonstrate the potential of full exposure of 'active sites' at the surface. Novel N-doped carbon coaxial nanocables with the pristine CNTs as the core and the N-doped carbon layers as the shell are proposed. The accessible and efficient utilization of the integrated nitrogen atoms enriched on the surface, together with the undestroyed intact inner walls, render the electrocatalyst much enhanced electrocatalytic activity and high electrical conductivity of 3.3 S cm−1, therefore, N-doped nanocables afford higher oxygen reduction current, ∼51 mV positively shift onset potential, low peroxide generation, as well as lower overpotential and higher current for oxygen evoluation reaction. [ABSTRACT FROM AUTHOR]

Non-precious Fe/N co-modified carbon electrocatalysts have attracted great attention due to their high activity and stability in oxygen reduction reaction (ORR). Compared to iron-free N-doped carbon electrocatalysts, Fe/N-modified electrocatalysts show four-electron selectivity with better activity in acid electrolytes. This is believed relevant to the unique Fe-N complexes, however, the Fe-N structure remains unknown. We used o,m,p-phenylenediamine as nitrogen precursors to tailor the Fe-N structures in heterogeneous electrocatalysts which contain FeS and Fe3C phases. The electrocatalysts have been operated for 5000 cycles with a small 39 mV shift in half-wave potential. By combining advanced electron microscopy and Mössbauer spectroscopy, we have identified the electrocatalytically active Fe-N6 complexes (FeN6, [FeIII(porphyrin)(pyridine)2]). We expect the understanding of the FeN6 structure will pave the way towards new advanced Fe-N based electrocatalysts. [ABSTRACT FROM AUTHOR]