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Defect-containing carbon nanotube materials were prepared by subjecting two commercial multiwalled carbon nanotubes (MWCNTs) of different purities to purification (HCl) and oxidative conditions (HNO3) and further heat treatment to remove surface oxygen groups. The as-prepared carbon materials were physicochemically characterized to observe changes in their properties after the different treatments. TEM microscopy shows morphological modifications in the MWCNTs after the treatments such as broken walls and carbon defects including topological defects. This leads to both higher surface areas and active sites. The carbon defects were analysed by Raman spectroscopy, but the active surface area (ASA) and the electrochemical active surface area (EASA) values showed that not all the defects are equally active for oxygen reduction reactions (ORRs). This suggests the importance of calculating either ASA or EASA in carbon materials with different structures to determine the activity of these defects. The as-prepared defect-containing multiwalled carbon nanotubes exhibit good catalytic performance due to the formation of carbon defects active for ORR such as edge sites and topological defects. Moreover, they exhibit good stability and methanol tolerances. The as-prepared MWCNTs sample with the highest purity is a promising defective carbon material for ORR because its activity is only related to high concentrations of active carbon defects including edge sites and topological defects. [ABSTRACT FROM AUTHOR]

2D materials are regarded as promising electrocatalysts for water splitting because of their advances in providing ample active sites and improving electrochemical reaction kinetics. 2D MoSe2 has a greater intrinsic electrical conductivity and lower Gibbs free energy for reactant adsorption. However, there is still room for improvement in the electrocatalytic performance of MoSe2 for high‐performance electrochemical water splitting devices. Herein, the in situ preparation of heterostructure made of covalently bonded MoSe2 and rGO is reported. The obtained electrocatalyst contains the aggregated 3D structured MoSe2 over rGO, which is covalently bonded together with more edge sites. The active edge sites of MoSe2/rGO are dynamically involved in the electrocatalytic activity while facilitating electron transfer. Hence, the MoSe2/rGO heterostructure requires a low cell voltage of 1.64 V to reach 100 mA cm−2 in water splitting with high reaction kinetics. The aggregated MoSe2 over rGO with more edge sites exposed by the 3D structure of MoSe2 and the interfacial covalent bond in between them provides a favorable electronic structure for the HER and OER with low overpotentials and high current densities and enhances the stability of the electrocatalyst. This work presents an attractive and cost‐effective electrocatalyst suitable for industrial‐scale hydrogen fuel production. [ABSTRACT FROM AUTHOR]

Abstract 2D materials are regarded as promising electrocatalysts for water splitting because of their advances in providing ample active sites and improving electrochemical reaction kinetics. 2D MoSe2 has a greater intrinsic electrical conductivity and lower Gibbs free energy for reactant adsorption. However, there is still room for improvement in the electrocatalytic performance of MoSe2 for high‐performance electrochemical water splitting devices. Herein, the in situ preparation of heterostructure made of covalently bonded MoSe2 and rGO is reported. The obtained electrocatalyst contains the aggregated 3D structured MoSe2 over rGO, which is covalently bonded together with more edge sites. The active edge sites of MoSe2/rGO are dynamically involved in the electrocatalytic activity while facilitating electron transfer. Hence, the MoSe2/rGO heterostructure requires a low cell voltage of 1.64 V to reach 100 mA cm−2 in water splitting with high reaction kinetics. The aggregated MoSe2 over rGO with more edge sites exposed by the 3D structure of MoSe2 and the interfacial covalent bond in between them provides a favorable electronic structure for the HER and OER with low overpotentials and high current densities and enhances the stability of the electrocatalyst. This work presents an attractive and cost‐effective electrocatalyst suitable for industrial‐scale hydrogen fuel production.

Defect-containing carbon nanotube materials were prepared by subjecting two commercial multiwalled carbon nanotubes (MWCNTs) of different purities to purification (HCl) and oxidative conditions (HNO3) and further heat treatment to remove surface oxygen groups. The as-prepared carbon materials were physicochemically characterized to observe changes in their properties after the different treatments. TEM microscopy shows morphological modifications in the MWCNTs after the treatments such as broken walls and carbon defects including topological defects. This leads to both higher surface areas and active sites. The carbon defects were analysed by Raman spectroscopy, but the active surface area (ASA) and the electrochemical active surface area (EASA) values showed that not all the defects are equally active for oxygen reduction reactions (ORRs). This suggests the importance of calculating either ASA or EASA in carbon materials with different structures to determine the activity of these defects. The as-prepared defect-containing multiwalled carbon nanotubes exhibit good catalytic performance due to the formation of carbon defects active for ORR such as edge sites and topological defects. Moreover, they exhibit good stability and methanol tolerances. The as-prepared MWCNTs sample with the highest purity is a promising defective carbon material for ORR because its activity is only related to high concentrations of active carbon defects including edge sites and topological defects.

The rational design of a stable and catalytic carbon cathode is crucial for the development of rechargeable lithium‐oxygen (LiO2) batteries. An edge‐site‐free and topological‐defect‐rich graphene‐based material is proposed as a pure carbon cathode that drastically improves LiO2 battery performance, even in the absence of extra catalysts and mediators. The proposed graphene‐based material is synthesized using the advanced template technique coupled with high‐temperature annealing at 1800 °C. The material possesses an edge‐site‐free framework and mesoporosity, which is crucial to achieve excellent electrochemical stability and an ultra‐large capacity (>6700 mAh g−1). Moreover, both experimental and theoretical structural characterization demonstrates the presence of a significant number of topological defects, which are non‐hexagonal carbon rings in the graphene framework. In situ isotopic electrochemical mass spectrometry and theoretical calculations reveal the unique catalysis of topological defects in the formation of amorphous Li2O2, which may be decomposed at low potential (∼ 3.6 V versus Li/Li+) and leads to improved cycle performance. Furthermore, a flexible electrode sheet that excludes organic binders exhibits an extremely long lifetime of up to 307 cycles (>1535 h), in the absence of solid or soluble catalysts. These findings may be used to design robust carbon cathodes for LiO2 batteries. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) is a promising electrocatalyst for hydrogen evolution reaction (HER). However, the exposed active edge sites of MoS2 are limited due to its intrinsic stacking property. Herein, a highly exposed MoS2 hybrid electrocatalyst is prepared by a confined strategy of the pores of a 2D metal‐organic framework (MOF). A low overpotential of 76 mV at 10 mA cm−2 and a Tafel slope of 73 mV dec−1 are achieved, which indicated greater efficiency than pristine MoS2. The denotative growth of MoS2 from the internal pore of 2D MOF on the surface effectively prevents its stacking and exposes much more active edge sites. Experimental results show that parts of Co are incorporated into MoS2, producing strong electronic interaction between Co and Mo atoms and accounting for the excellent HER activity of MoS2. This work demonstrates a confined strategy to prepare nanomaterials with highly exposed edge sites and enhanced intrinsic activity. [ABSTRACT FROM AUTHOR]

Two‐dimensional covalent organic frameworks (2D COFs) are often employed for electrocatalytic systems because of their structural diversity. However, the efficiency of atom utilization is still in need of improvement, because the catalytic centers are located in the basal layers and it is difficult for the electrolytes to access them. Herein, we demonstrate the use of 1D COFs for the 2e− oxygen reduction reaction (ORR). The use of different four‐connectivity blocks resulted in the prepared 1D COFs displaying good crystallinity, high surface areas, and excellent chemical stability. The more exposed catalytic sites resulted in the 1D COFs showing large electrochemically active surface areas, 4.8‐fold of that of a control 2D COF, and thus enabled catalysis of the ORR with a higher H2O2 selectivity of 85.8 % and activity, with a TOF value of 0.051 s−1 at 0.2 V, than a 2D COF (72.9 % and 0.032 s−1). This work paves the way for the development of COFs with low dimensions for electrocatalysis. [ABSTRACT FROM AUTHOR]

In the past decades, toxic gas emissions have increased significantly owing to the rapid growth of industry and road transportation. Therefore, monitoring major pollutants, such as NO2, is crucial to protecting human health. The 2D materials that contain numerous adsorption sites and exhibit ultrahigh chemical reactivity can be used as sensor materials to detect these toxic gases. Herein, highly uniform, large‐area carbon‐incorporating hierarchical MoS2 nanobranches are synthesized by metal–organic chemical vapor deposition (MOCVD). An in situ carbon‐incorporation method that uses the carbon impurity present in the precursor as the seed during the MOCVD process is employed to form a hierarchical structure containing abundant adsorption sites. A gas sensor based on the resulting C‐MoS2 nanobranches contains many edge sites exhibits high adsorption energy, and consequently, has high NO2 gas sensitivity. Hence, this hierarchical C‐MoS2 gas sensor shows excellent sensing properties, exhibiting a device response of 1.67 at an extremely low NO2 concentration (≈5 ppb). The limit of detection of the gas sensor for NO2 is calculated to be low (≈1.58 ppt), further confirming its exceptional performance. Thus, the hierarchical C‐MoS2 nanobranches deposited herein provide novel insights regarding the properties of 2D materials and are highly suited for fabricating high‐performance NO2 sensors.

Abstract The rational design of a stable and catalytic carbon cathode is crucial for the development of rechargeable lithium‐oxygen (LiO2) batteries. An edge‐site‐free and topological‐defect‐rich graphene‐based material is proposed as a pure carbon cathode that drastically improves LiO2 battery performance, even in the absence of extra catalysts and mediators. The proposed graphene‐based material is synthesized using the advanced template technique coupled with high‐temperature annealing at 1800 °C. The material possesses an edge‐site‐free framework and mesoporosity, which is crucial to achieve excellent electrochemical stability and an ultra‐large capacity (>6700 mAh g−1). Moreover, both experimental and theoretical structural characterization demonstrates the presence of a significant number of topological defects, which are non‐hexagonal carbon rings in the graphene framework. In situ isotopic electrochemical mass spectrometry and theoretical calculations reveal the unique catalysis of topological defects in the formation of amorphous Li2O2, which may be decomposed at low potential (∼ 3.6 V versus Li/Li+) and leads to improved cycle performance. Furthermore, a flexible electrode sheet that excludes organic binders exhibits an extremely long lifetime of up to 307 cycles (>1535 h), in the absence of solid or soluble catalysts. These findings may be used to design robust carbon cathodes for LiO2 batteries.

The morphology and active site engineering of electrocatalysts is an efficient strategy to improve the intrinsic activity and selectivity of electrocatalytic CO2 reduction. Here the ultralong and thin Bi nanobelts (Bi‐NBs) are fabricated, which feature a high edge‐to‐facet ratio and high‐degree connectivity is inherited from the ultrahigh‐aspect‐ratio crystalline bismuth−organic hybrid nanobelts, through a cathodically in situ reconstruction process. The unique nanostructure of Bi‐NBs leads to a significantly enhanced performance for electrocatalytic CO2 reduction with a near‐unity formate selectivity and high formate partial current density, which is far superior to those of the discrete Bi counterparts with low edge‐to‐facet ratios. Notably, Bi‐NBs perform ultrahigh formate selectivity over a broad potential window with a high current density reaching 400 mA cm−2 for formate production in a flow cell. Moreover, it is ultrastable to continuous electrolysis for nearly 23 h at 200 mA cm−2 without compromising the selectivity. Based on calculations, the enhanced performance is closely related to the high edge‐to‐facet ratio of Bi‐NBs, since the rich edge sites are conducive to the stabilization of the key *OCHO intermediate for formate production. In addition, the ultralong and interconnected Bi‐NBs provide "expressways" for electron transfer during CO2 electroreduction, further contributing to the improved performance. [ABSTRACT FROM AUTHOR]

• The pristine MoS 2 synthesized hydrothermally contains MoO 3 by-product and amorphous MoS x. • During the initial 10 min of UVO treatment, there is an increase a significant increase of 2H MoS 2 and oxygen-incorporated amorphous MoS x , along with the disappearance of MoO 3. • UVO treatment for up to 30 min leads to a significant increase in 2H-MoS 2 , as the Mo:S stoichiometric ratio approaches the ideal value and boosts the presence of MoS 2 edge sites. • Extending UVO treatment to 50 min reduces the crystallinity of 2H-MoS 2 by creating an abundance of defects and increased amorphous oxygen-incorporated MoS x. • A 50-min UV ozone treatment results in a substantial reduction in the onset potential to 116 mV, coupled with achieving the lowest Tafel slope of 64 mV/dec. Electrochemical water splitting, a key process for extracting hydrogen energy from water, is recognized as a promising eco-friendly technology. Molybdenum disulfide (MoS 2), especially when possessing abundant defects, emerges as a cost-effective and efficient catalyst for hydrogen evolution reaction (HER), presenting a viable alternative to noble metals such as platinum (Pt). However, the impact of UV-Ozone (UVO) in generating defects in bulk 2H-MoS 2 remains underexplored. Here, we successfully synthesized 2H-MoS 2 using the hydrothermal method on a 3D conductive carbon cloth. Subsequently, the sample underwent UVO treatment for three different durations of 10, 30, and 50 min. Our results demonstrate that a 50-minute exposure to UVO yields the most effective HER performance, with a significant decrease in the onset potential from 189 mV to 116 mV and a low Tafel slope of 64 mV/decade. This enhancement is attributed to increased surface activity, evident in a more than fourfold increase in double-layer capacitance (C dl). Importantly, the 50-minute UVO treatment not only significantly improves the purity of MoS 2 and increases the number of edge sites, but also lead to an increase in sulfur vacancies and the formation of amorphous oxygen-incorporated MoS x. These edge sites, along with sulfur vacancies and oxygens incorporation, are considered ideal for hydrogen binding, enhancing electron transport, and improving HER activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • SnS 2 flakes were deposited vertically to enhance the gas adsorption sites. • Vertical flakes are evidenced from the Raman peak intensity ratio and HRSEM analysis. • Negative curvatures with high surface energy upsurge the responsive reactive sites. • Maximum response of 98 % is achieved at RT without any dopants/heterojunctions. SnS 2 (Tin sulfide), a 2D layered material has been recognized as the most promising material for gas sensing applications owing to its high surface-to-volume ratio. Controlling the growth orientation provides them with remarkably high catalytic activity and better adsorption properties. In this work, SnS 2 is deposited on SiO 2 / S i by chemical vapor deposition (CVD) technique. The calculated peak intensity ratio from Raman A 1 g E g > E g A 1 g and HRSEM analysis confirms the vertical growth of SnS 2. The band bending (q V) was found to be increased as a function of NO 2 concentration, resulting in an excellent response (S %) of about 98 % towards 40 ppm of NO 2 at room temperature (30 °C). It also has the characteristics of low limit of detection (LoD) of 1.29 ppm and long-term reliable stability of 28 days with 81 % retention of performance. The obtained sensing performance can be attributed towards the presence of voids, negative curvature and high adsorption of NO 2 on edge sites of vertically grown SnS 2. Thus, exploiting the inherent property of the layered materials using growth strategy will provide a way to develop the potential applicant for practical NO 2 detector. [ABSTRACT FROM AUTHOR]

2D materials exhibit strong physical orientation‐dependent properties due to their intrinsic anisotropic crystallinity. Herein, the authors review the recent developments on the properties, preparation, and applications of emerging vertically aligned 2D materials. This report initially discusses the various properties of vertically aligned materials such as electronic, optical, magnetic, thermal, mechanical, and super wetting. The tuning of these properties is also highlighted based on strategies such as scale, doping, defect, vacancy, intercalation, and phase engineering. Then, this review provides a succinct and critical survey of the recent progress in designing, preparation techniques, and the manufacturing conditions of vertically aligned materials. After investigating the properties, tunability of properties, and preparation methods for vertically aligned 2D materials, their performances in numerous applications are comprehensively summarized. The presence of predominantly exposed edge sites significantly alters their properties and chemical reactivity owing to their enriched dangling bonds and offers several advantages for a wide range of applications including chemical and gas sensors, field emission, energy storage, catalysis, and optoelectronic devices. Finally, some developmental challenges, a few outlooks, future possibilities, and directions are summarized to inspire readers toward exploring vertically aligned 2D materials with new advances and functionalities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic effect of carbon edges and dopants towards ORR was predicted by DFT. • Well-designed N -GNRs contain both heteroatom-doping and abundant edge sites. • Best ORR property was obtained for N -GNRs compared to other control samples. • The synergistic effect was again demonstrated by experimental facts. Decoration with alien atoms and increasing the edge content are two valid ways to activate the oxygen reduction reaction (ORR) property of nanocarbons. To further enhance their intrinsic activity and explore the underlying ORR mechanism, graphene nanoribbons (GNRs) were selected as an ideal catalyst model. Theoretical simulations have predicted that with the synergistic effect between heteroatom-doping and edge sites, the ORR activity can be significantly improved. Inspired by this, N -GNRs were synthesized via the oxidative unzipping of CNTs followed by nitrogen incorporation with urea. Ample edges and nitrogen doping sites were detected by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. As a result, N -GNRs exhibited remarkably higher ORR properties in terms of onset and half-wave potentials, Tafel slopes, electron transfer number and methanol tolerance than either GNRs, the control sample without doping, or N -CNTs, the control sample without abundant edges, simply clarifying the significance of synergy between dopants and edges. Thus, this work provides a simple but efficient strategy to fabricate high-performance oxygen reduction catalysts. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) geochemical behavior is strongly influenced by its adsorption onto natural phyllomanganates, which contain both layer edge sites and vacancies; however, Cd isotope fractionation mechanisms at these sites have not yet been addressed. In the present work, Cd isotope fractionation during adsorption onto hexagonal (containing both types of sites) and triclinic birnessite (almost only edge sites) was investigated using a combination of batch adsorption experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy, surface complexation modeling, and density functional theory (DFT) calculations. Light Cd isotopes are preferentially enriched on solid surfaces, and the isotope fractionation induced by Cd 2+ adsorption on edge sites (Δ 114/110 Cd edge-solution = -1.54 ± 0.11‰) is smaller than that on vacancies (Δ 114/110 Cd vacancy-solution = -0.71 ± 0.21‰), independent of surface coverage or pH. Both Cd K-edge EXAFS and DFT results indicate the formation of double corner-sharing complexes on layer edge sites and mainly triple cornering-sharing complexes on vacancies. The distortion of both complexes results in the negative isotope fractionation onto the solids, and the slightly longer first Cd-O distances and a smaller number of nearest Mn atoms around Cd at edge sites probably account for the larger fractionation magnitude compared to that of vacancies. These results provide deep insights into Cd isotope fractionation mechanisms during interactions with phyllomanganates.

[Display omitted] • Hydrodesulfurization mechanisms of dibenzothiophene (DBT) elucidated on CoMoS edges. • Hydrogenolysis and dihydrogenation are kinetically favored on Co promoted M-edge. • C S scission via β–elimination exhibits moderate activation barriers on promoted S-edge. • Key role of S 2 dimer during β–elimination of H from α,β–dihydrogenated DBT. • Synergy between cobalt promoted M-edge and S-edge. Unraveling the mechanisms of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and the corresponding active sites represents a scientific challenge to improve the intrinsic performances of Co-promoted MoS 2 (CoMoS) catalysts. By using density functional theory calculations, we compare two historical mechanisms for the C S bond scission of DBT (direct desulfurization): direct hydrogenolysis of DBT and β–elimination of α,β–dihydro-diobenzothiophene (α,β–DHDBT) on four relevant sites of the two CoMoS M- and S-edges. On the Co promoted M-edge, the α,β–DHDBT is formed through dihydrogenation which is kinetically competing with hydrogenolysis (both exhibiting activation free energies, ΔG‡, smaller than +1.24 eV). On the S-edge, both dihydrogenation and hydrogenolysis exhibit higher ΔG‡ (>+1.78 eV). Interestingly, on the S-edge, the β–elimination (E2 type) on the α,β–DHDBT is found to be kinetically competing (ΔG‡ = +1.14 eV). The elimination of H β atom involves a S 2 dimer close to the S-vacancy site where DHDBT is adsorbed. Since this leaving H β atom is distinct from the one added at dihydrogenation step, this may explain why direct desulfurization of 4,6-alkyl substituted DBT compounds is hampered according to the elimination mechanism. We finally discuss the possible synergy between the two edges of CoMoS for HDS of DBT. [ABSTRACT FROM AUTHOR]

To mitigate the energy crisis and environmental pollution, efficient and earth‐abundant hydrogen evolution reaction (HER) electrocatalysts are essential for hydrogen production through electrochemical water splitting. Graphene‐based materials as metal‐free catalysts have attracted significant attention but suffer from insufficient activity and stability. Therefore, a novel and economical approach is developed to prepare highly active, robust, and self‐supported reduced graphene oxide (rGO)/SiO2 ceramic composites as electrocatalysts in HER. Through intercalation and pressure sintering, the rGO sheets are parallelly aligned and embedded into a dense and chemically inert SiO2 matrix, ensuring the electrical conductivity and stability of the prepared composites. After directional cutting, the edges of the oriented rGO sheets become fully exposed on the composite surface, acting as highly electrocatalytic active sites in HER, as confirmed by density functional theory calculations. The 4 vol% rGO/SiO2 composite displays superior electrocatalytic performance, featuring a low overpotential (134 mV) at a current density of 10 mA cm−2, a small Tafel slope (103 mV dec−1), and excellent catalytic durability in 0.5 m H2SO4. This study provides a new yet cost‐effective strategy to prepare metal‐free, robust, and edge‐rich rGO/ceramic composites as a highly electrocatalytic active catalyst for HER applications. [ABSTRACT FROM AUTHOR]

A direct spectroscopic observation of CO 2 methanation over the Re cluster edge sites, where CO 2 was reduced to CO via redox pathway followed by hydrogenation to methane. [Display omitted] • A direct spectroscopic observation of CO 2 methanation over the Re cluster edge sites, where CO 2 reduce to CO via redox pathway followed by hydrogenation to methane. • Identified and explain the size dependent activity of CO 2 methanation. • The rate-determining step in CO 2 methanation relates to the reactivity and stability of intermediate CO, rather than the activation of CO 2 or H 2. CO 2 methanation on heterogeneous catalysts holds great significance in achieving the net-zero emission target. However, understanding the atomic-scale relationship between reactivity and active site has been a subject of debate. The study investigated CO 2 methanation reaction catalyzed by Re/TiO 2 catalysts and identified the active site distribution and its relationship with reactivity. The low-coordinated edge sites of Re nanoparticle were found to be the active sites where CO 2 dissociated into CO via a carbide pathway and subsequently hydrogenated to form methane. Furthermore, the study revealed that the size of Re nanoparticle influenced the distribution of active edge sites and affected the reactivity and stability of the CO intermediate, which was the rate-determining step in CO 2 methanation reaction. Controlling the size and structure of Re nanoparticle can, therefore, enhanced the activity and efficiency of CO 2 methanation reaction. The identification of these active sites and the insights gained from this study have significant implications for the mechanistic understanding and optimization of CO 2 methanation over Re/TiO 2 catalysts. It provides a basis for designing more effective catalysts to facilitate the conversion of CO 2 to methane, thereby contributing to the goal of achieving net-zero emissions. [ABSTRACT FROM AUTHOR]

Manganese oxides and organic acids are key factors affecting arsenic mobility, but As(III) oxidation and adsorption in the coexistence of birnessite and low molecular weight organic acids (LMWOAs) are poorly understood. Herein, As(III) immobilization by birnessite was investigated with/without LMWOAs (including tartaric (TA), malate (MA), and succinic acids (SA) with two, one and zero hydroxyl groups, respectively). In the low-As(III) system with less Mn(II) production, LMWOAs generally inhibited As(III) oxidation. The slower decrease in As(III) concentration in TA-amended batches resulted from stronger bonding interaction between TA and edge sites, evidenced by higher removal of TA than MA and SA in solutions and the higher proportion of shifted C-OH component in solids. In high-As(III) systems with abundant Mn(II) production, higher concentrations of dissolved Mn and Mn(III) in LMWOA-amended batches than in LMWOA-free batches revealed that LMWOA-induced complexing dissolution caused the release of adsorbed Mn(II), which was conducive to As(III) oxidation and As(V) adsorption onto the edge sites. The lowest concentrations of dissolved Mn and Mn(III) in TA-amended batches indicated that the hydroxyl group constrained complexing dissolution. This study reveals that concentrations of produced Mn(II) determined the roles of LMWOAs in As(III) behavior and highlights the impacts of the hydroxyl group on arsenic mobility. [Display omitted] • Strong binding interaction between LMWOA and edge sites led to slow As(III) oxidation. • Hydroxyl group-promoted ternary complex weakened inhibition of As(V) adsorption. • Complexing dissolution promoted As(III) oxidation and As(V) adsorption. • Hydroxyl group constrained LMWOA-induced complexing dissolution. [ABSTRACT FROM AUTHOR]

Highly active anemone-like MoS 2 catalyst was vertically and directly deposited on fluorine-doped tin oxide (FTO) substrate via a straightforward facile hydrothermal method with excellent adhesion and appreciable stability for hydrogen evolution reaction (HER). MoS 2 catalyst with unique morphology full of active edge sites and surface areas was fabricated by varying synthesis time and specific concentration of precursors. Structural characteristics were investigated by X-ray diffraction pattern (XRD), and Raman spectroscopy. Field emission scanning electron microscopy (FESEM) images show the variation of morphology during synthesis time as a very important factor in the preparation process. It also reveals the lamellar structure of anemone-like MoS 2 with an average thickness of ~19 nm. Electrochemical tests including linear sweep voltammetry and electrochemical impedance spectroscopy were carried out. These tests suggest a high electrocatalytic activity for MoS 2 /FTO electrode toward HER with a charge transfer resistance (R ct) about 24 Ω, a Tafel slope of ~87 mV dec−1, and an exchange current density of 0.063 mA cm−2 for the optimum sample synthesized at 20 h during hydrothermal process. The catalytic activity of the samples for HER was carefully investigated and proposed in detailed discussions according to the Mott-Schottky equation for the first time. Based on Mott-Schottky analysis, the obtained samples are n-type semiconductors and the density of carriers (N D) of samples was calculated. N D of the optimum sample (sample B) obtained (2.23 ± 0.055) × 1017. Fabricated samples have good stability proved by repeating LSV test for 1000 cycles. This work optimizes the catalytic activity of the bare MoS 2 with a cost-effective, easy, and binder-free method. It is a promising base for future works on MoS 2 catalysts. Image 1 • A unique morphology of MoS 2 nanostructure on FTO was obtained. • Fluffy anemone-like MoS 2 deposited on FTO without using any binder. • HER activity was investigated according to the Mott-Schottky equation. [ABSTRACT FROM AUTHOR]

The rational design of transition‐metal sulfide with two‐dimensional (2D) structure and tunable edges on the nanoscale can effectively improve their activity for variously catalytic reactions. Herein, the 2D PbS nanosheets with abundant zigzag edges (e‐PbS NS), which exhibited an excellent performance for CO2 photoconversion to CO, were constructed. The zigzag edges on the PbS NS are beneficial for exposing more active sites and promoting charge separation, thereby accelerating the kinetics process of CO2 photoreduction. This study provides a strategy to regulate structure with effective edge sites for the CO2 reduction. [ABSTRACT FROM AUTHOR]

The abundance of available surface chemical information and edge structures of carbon materials have attracted tremendous interest in catalysis. For the oxygen evolution reaction (OER), the edge effects of carbon materials have rarely been studied in detail because of the complexity of various coexisting edge configurations and the controversy between carbon corrosion and carbon catalysis. Herein, the exact roles of common carbon active edge sites in the OER were interrogated using polycyclic aromatic hydrocarbons (PAHs) with designated configurations (zigzag and armchair) as model probe molecules, with a focus on structure–function relationships. Zigzag configurations of PAHs showed high activity for the OER while also showing a good stability at a reasonable potential. They show a TOF value of 0.276 s−1 in 0.1 m KOH. The catalytic activity of carbon edge sites was further effectively regulated by extending the π conjugation structure at a molecular level. [ABSTRACT FROM AUTHOR]

Developing efficient electrocatalysts from the earth‐abundant transition‐metal family is a great challenge for overall water splitting. Herein, we developed an approach to regulate the morphology and electronic structure of α‐Co0.9Fe0.1(OH)x nanoplates, in which FeCl2 (as a precursor) plays a significant role under reflux conditions. The resulting 2D α‐Co0.9Fe0.1(OH)x nanoplates exhibit more accessible edge active sites and more high‐valence Co species to boost its intrinsic activity. Therefore, this electrocatalyst shows outstanding oxygen evolution reaction performance (with an overpotential of 225 mV at 10 mA cm−2 and a Tafel slope of 39 mV dec−1 and good stability) and excellent activity toward the hydrogen evolution reaction (with an overpotential of 122 mV at 10 mA cm−2) in 1M KOH solution. When employed as bifunctional electrocatalysts on both the anode and cathode for overall water splitting, α‐Co0.9Fe0.1(OH)x can afford 10 mA cm−2 at 1.62 V with long‐term stability. The one‐pot synthesis of 2D Fe‐doped transition‐metal hydroxide nanoplates enriched with abundant edge sites may provide a new strategy for fabricating efficient overall water splitting catalysts. [ABSTRACT FROM AUTHOR]

The identification of the contribution of different surface sites to the catalytic activity of a catalyst nanoparticle is one of the most challenging issues in the fundamental studies of heterogeneous catalysis. We herein demonstrate an effective strategy of using a series of uniform cubic Cu2O nanocrystals with different sizes to identify the intrinsic activity and contributions of face and edge sites in the catalysis of CO oxidation by a combination of reaction kinetics analysis and DFT calculations. Cu2O nanocrystals undergo in situ surface oxidation forming CuO thin films during CO oxidation. As the average size of the cubic Cu2O nanocrystals decreases from 1029 nm to 34 nm, the dominant active sites contributing to the catalytic activity switch from face sites to edge sites. These results reveal the interplay between the intrinsic catalytic activity and the density of individual types of surface sites on a catalyst nanoparticle in determining their contributions to the catalytic activity. Choose your site: The dominant active site of CuO thin films on cubic Cu2O nanocrystals contributing to the catalytic oxidation of CO switches from face sites for large nanocrystals to edge sites for small ones. This reveals the interplay between the intrinsic catalytic activity and the density of individual types of surface sites on a catalyst nanoparticle. [ABSTRACT FROM AUTHOR]

Abstract Birnessites are abundant naturally occurring minerals with high sorption and oxidation capacity that could therefore play an important role in antimony (Sb) migration and transformation. There are various types of birnessites in the environment. However, little is known about the similarities and differences in Sb oxidation and sorption on birnessites with different properties. In this study, the behavior of Sb oxidation and sorption on two contrasting birnessites (δ-MnO 2 and triclinic birnessite (TrBir)) were investigated via batch and kinetic experiments and various spectroscopic techniques. Our results showed that the reaction mechanisms between Sb and the two birnessites were similar. The edge sites of birnessites were responsible for Sb(III) oxidation. Mn(IV) was reduced to Mn(III) and Mn(II), bound with birnessites and released to the solution, respectively. Because of the rapid rate of electron transfer of adsorbed Sb(III) to birnessites, the only Sb species on δ-MnO 2 after the oxidation reaction was Sb(V). Sb(V) was adsorbed at the edge sites of birnessites by replacing the OH group of birnessites, forming corner-sharing complexes with birnessites. However, the Sb sorption and oxidation capacities of the two birnessites were significantly different. Poorly-crystallized δ-MnO 2 exhibited a much higher oxidation and sorption capacity than well-crystallized TrBir because the former had many more edge sites than the latter. This study reveals the general mechanism of the reaction between Sb and birnessite and indicates that birnessite with a high number of edge sites would exhibit a huge capacity in Sb oxidation and sorption. Graphical abstract Image 1 Highlights • The reaction mechanisms between Sb and the two birnessite (δ-MnO 2 and TrBir) are similar. • The edge sites of birnessite were responsible for Sb(III) oxidation and Sb(V) sorption. • Sb(V) was adsorbed at the edge sites of birnessite, forming corner-sharing complexes with birnessite. • δ-MnO 2 was much reactive than TrBir in Sb oxidation and adsorption due to the many more edge sites of δ-MnO 2. The general reaction mechanism between Sb and birnessite and the key properties of birnessite affecting the reaction were revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1T−Mn−VS 2 @Co 2 P@CC was synthesized by hydrothermal fallowed to CVD method. • Synergism of 1T−Mn−VS 2 and Co 2 P enhances the overall water splitting. • DFT validates defect engineering with interface modeling for fast charge transfer. • As-synthesized catalyst exhibits 98 and 250 mV for HER and OER at 10 mA cm−2. • 1T−Mn−VS 2 @Co 2 P@CC electrolyzer exhibits excellent 100 h stability at 500 mA cm−2. The rational integration of a 2D layered transition metal sulfide and phosphide in a single heterostructure can bring a breakthrough to produce hydrogen through controlled manipulation of electronic structure. Here, we report a novel design of a hierarchical 2D−2D tangled 3D heterostructure of manganese-doped 1T vanadium disulfide (1T−Mn−VS 2), assembled with cobalt phosphide (Co 2 P), at the flexible carbon cloth as 1T−Mn−VS 2 @Co 2 P@CC. The HER active 1T−Mn−VS 2 bearing catalytically active edge sites, with numbers of basal planes and OER active Co 2 P, create synergism and hastening rection kinetics towards bifunctional water splitting. The heterostructure display significantly low over potential of 98 and 250 mV for HER and OER at 10 mA cm−2. The 1T−Mn−VS 2 @Co 2 P@CC (+,-) electrochemical cell needs 1.50 V to reach a current density of 10 mAcm−2. The implication of defect engineering along with interface modeling validated by DFT study, induces the regulation of electronic structure for fast redistribution of local charges/electron transfer. [ABSTRACT FROM AUTHOR]

Electrolysis of water offers an efficient and eco-friendly route to separate hydrogen isotopes and cathode electrocatalysts featuring high separation factors coupled with high activity and stability are increasingly in demand. In this work, we propose MoS 2 rich in edge sites (MoS 2 -RS) as a promising hydrogen isotope separation electrocatalyst for the first time. MoS 2 -RS cathode exhibits high activity and hydrogen isotope selectivity with a low overpotential of 182.4 mV at 10 mA cm−2, a small Tafel slope of 61 mV dec−1 and a high hydrogen-deuterium separation factor (S H/D) of 10.22 in contrast to 6.33 for the commercial Pt/C catalyst. Density functional theory calculations ascribe the high selectivity of MoS 2 -RS to the H/D zero-point energy difference. Moreover, MoS 2 -RS demonstrates much higher values of S H/D compared with Pt/C catalyst under all test conditions and good long-term stability under acidic conditions. This work not only provides a promising catalytic material for efficient electrolytic separation of hydrogen isotopes but also indicates the direction of rational design of it. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Electrochemical CO 2 reduction has been considered as a promising route for renewable energy storage and carbon-neutral energy cycle. However, the selectivity and stability of electrocatalysts for CO 2 reduction need to be improved. Two-dimensional (2D) layered electrocatalysts with high conductivity and abundant active sites have been considered as good candidates for CO 2 reduction. Herein, we propose a liquid-exfoliation strategy to prepare ultrathin 2D bismuth (Bi) nanosheets towards efficient electrocatalytic CO 2 conversion. Compared with bulk Bi, the increased edge sites on ultrathin Bi nanosheets played a vital role in CO 2 adsorption and reaction kinetics, significantly facilitating CO 2 -to-formate (HCOOH/HCOO-) conversion. Through density functional theory (DFT) calculation, we found that the *OCOH formation step tended to occur on edge sites rather than on facet sites, as confirmed by the lower Gibbs free energies. Benefited from the high conductivity and rich edge sites, Bi nanosheets exhibited a Faradaic efficiency of 86.0% for formate production and a high current density of 16.5 mA cm−2 at − 1.1 V (vs. RHE), much superior to bulk Bi. Moreover, the Bi nanosheets could maintain well-preserved catalytic activity after long-term testing for over consecutive 10 h. We hope this study may provide new insights for the fabrication of novel 2D nanostructured metals for highly-efficient and long-life electrocatalytic CO 2 conversion. Graphical abstract fx1 Highlights • Liquid-phase exfoliated ultrathin Bi nanosheets was prepared. • Ultrathin Bi nanosheets show significantly enhanced electrocatalytic CO 2 reduction. • Possible mechanism and DFT calculations for the improved CO 2 RR was proposed. [ABSTRACT FROM AUTHOR]

Abstract: The important role of edge sites in atomically thin 2D materials serving as catalysts is already of concerned in plenty of material systems and catalytic reactions, whereas comprehensive study of the edge sites in 2D noble‐metal nanocatalysts is still lacking. Herein, for the first time, a controllable etching approach to tailor the fractal dimensions and edge sites of Pd nanosheets is developed and the edge sites in these 2D nanostructures from both structural and chemical aspects are investigated. The as‐tailored 2D Pd nanostructures with extra edge sites exhibit substantially enhanced electrocatalytic performance for the formic acid oxidation reaction (FAOR). Moreover, careful analysis of the results from electrocatalytic measurements reveals that the specific activities for the edge sites in the 2D nanostructures far exceed the activities for the low‐index planes of Pd and even dominate the overall activity exhibited by the 2D noble‐metal catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Improving the electrochemical properties of graphene aerogels (GAs) without doping or making composites is an attractive synthetic strategy. In this work we report some effects of graphene sheet dimensions on the properties of GAs. Nanographene aerogels (nG‐AGs) were synthesized using nanographene oxide (nGO) powder with a mean platelet diameter of 90 nm. In‐situ Fourier tranformation infrared (FTIR) spectroscopy during gelation revealed a longer fast‐gelation regime for nG‐AGs than for standard graphene aerogels (stdG‐AGs). The surface‐area‐normalized capacitance of nG‐AGs calculated from cyclic voltammetry is 16% higher than that of stdG‐AGs, and the onset of hydrogen evolution is observed at a lower over‐potential. These observations can be attributed to an increased density of edge sites and defects in nanographene sheets. Our results indicate that the diameter of the precursor graphene sheets can be used as a parameter to optimize the electrochemical properties of GAs depending on the application. [ABSTRACT FROM AUTHOR]

The presence of kaolinite, montmorillonite, and illite in packed quartz sand inhibited the transport of graphene oxide to different degrees. Transport inhibition was exerted mainly by the presence of positively charged sites on clay edges (which served as favorable deposition sites), whereas the effects on the overall particle-collector interaction energy and flow path were small. Kaolinite exhibited the most significant transport-inhibition effects because of its high percentage of edge area. Environ Toxicol Chem 2017;36:655-660. © 2016 SETAC [ABSTRACT FROM AUTHOR]

With first-principles calculations, we find a new strategy for developing high-performance catalysts for hydrogen evolution reaction (HER) via controlling the morphology and size of nanopolygons of monolayer transition-metal dichalcogenides (npm-MS2, with M = Mo, W, or V). Particularly, through devising a quantitative method to measure HER-active sites per unit mass and using such HER site density to comparatively gauge npm-MS2 performance, we identify three keys in making npm-MS2 with optimal HER performance: (a) npm-MS2 should be triangular with each edge being M-terminated and each edge-M atom passivated by one S atom; (b) each edge of npm-MoS2 and WS2 should have 5-6 metal atoms as HER site density drops below/above these sizes optimal both for HER and practical npm growth; and (c) npm-VS2 is immune to this overly fastidious size dependence. Known experimental data on npm-MoS2 indeed support the plausibility of practicing these design rules. We expect that raising the nucleation density and controlling the growth time to favor the production of our proposed ultrasmall npm-MS2 are critical but practical. Research on npm-VS2 would bear the highest impact because of its size-forgiving HER performance and relatively high abundance and low cost. [ABSTRACT FROM AUTHOR]

Developing green heterogeneous catalysts with excellent Fenton-like activity is critical for water remediation technologies. However, current catalysts often rely on toxic transitional metals, and their catalytic performance is far from satisfactory as alternatives of homogeneous Fenton-like catalysts. In this study, a green catalyst based on Zn single-atom was prepared in an ammonium atmosphere using ZIF-8 as a precursor. Multiple characterization analyses provided evidence that abundant intrinsic defects due to the edge sites were created, leading to the formation of a thermally stable edge-hosted Zn-N 4 single-atom catalyst (ZnN 4 -Edge). Density functional theory calculations revealed that the edge sites equipped the single-atom Zn with a super catalytic performance, which not only promoted decomposition of peroxide molecule (HSO 5 - ) but also greatly lowered the activation barrier for • OH generation. Consequently, the as-prepared ZnN 4 -Edge exhibited extremely high Fenton-like performance in oxidation and mineralization of phenol as a representative organic contaminant in a wide range of pH, realizing its quick detoxification. The atom-utilization efficiency of the ZnN 4 higher than an equivalent amount of the control sample without edge sites (ZnN 4 higher than an equivalent amount of the control sample without edge sites (ZnN 4 ), and the turnover frequency was ~10 3 times of the typical benchmark of homogeneous catalyst (Co 2+ ). This study opens up a revolutionary way to rationally design and optimize heterogeneous catalysts to homogeneous catalytic performance for Fenton-like application.

Nanomaterials with unique edge sites have received increasing attention due to their superior performance in various applications. Herein, we employed an effective ethylenediaminetetraacetic acid (EDTA)-assisted method to synthesize a series of exotic BiSe nanostructures with distinct edge sites. It was found that the products changed from smooth nanoplates to half-plate-containing and crown-like nanoplates upon increasing the molar ratio of EDTA to Bi. Mechanistic studies indicated that, when a dislocation source and relatively high supersaturation exist, the step edges in the initially formed seeds can serve as supporting sites for the growth of epilayers, leading to the formation of half-plate-containing nanoplates. In contrast, when the dislocation source and a suitably low supersaturation are simultaneously present in the system, the dislocation-driven growth mode dominates the process, in which the step edges form at the later stage of the growth responsible for the formation of crown-like nanoplates. [ABSTRACT FROM AUTHOR]

The selective hydrodesulfurization (HDS) of FCC gasoline is a key catalytic process for reducing sulfur content in gasoline. In the present work, we focus on the effect of H 2 O amount alone or in mixture with CO on the transformation of a model FCC gasoline composed of 2-methylthiophene (2MT) and 2,3-dimethylbut-2-ene (23DMB2N) molecules, over an alumina supported CoMoS catalyst. A negative impact of water and CO on the conversion of 2MT and 23DMB2N is found. However the effect in the presence of CO is much stronger. The comparison of Density Functional Theory (DFT) calculations of CO and water adsorption on the S- and M-edge sites of the CoMoS slabs shows a significantly stronger CO adsorption energy than water adsorption energy. When CO and water were introduced simultaneously, the negative impact observed in the transformation of the model feed is mainly due only to the presence of CO. However whatever the oxygenated molecules used and their amount, no impact in the selectivity measured by the ratio between the activity in hydrodesulfurization and in hydrogenation is observed. [ABSTRACT FROM AUTHOR]

CO dissociation rate is fundamental for determining selectivity and yield for growing carbon chains on iron catalysts in, e.g., Fischer–Tropsch and carbon nanotube syntheses. CO dissociation is a highly structure sensitive reaction; on crystal surfaces and large particles CO dissociation is facile only at step sites. However, small (<3 nm) nanoparticles cannot contain steps and even in macroscopic clusters step concentration is small. Here, density functional theory is used systematically to map several CO dissociation pathways to find and explain the nature of active sites in small BCC iron nanoclusters. It is shown that BCC(100-110) edges of the particle are responsible for the reactivity of small Fe–BCC clusters and that low CO dissociation barrier is achievable even without stepped surfaces. Careful analysis proves the essential role of local geometry at the active site leading to strong interaction between the metal and 2π* orbitals and accessible, empty states. Furthermore, CO dissociation on Fe–BCC particles is more facile than on smooth crystal surfaces and icosahedral and amorphous iron particles exemplifying the importance of nanoparticle geometry on reactivity. Providing suitable particle geometry is used, CO dissociation on Fe–BCC nanoparticles occurs even under mild conditions, enabling controlled synthesis of carbon structures from CO. [ABSTRACT FROM AUTHOR]

Nanocrystalline or amorphous cobalt oxyhydroxides (CoCat) are promising electrocatalysts for the oxygen evolution reaction (OER). While having the same short-range order, CoCat phases possess different electrocatalytic properties. This phenomenon is not conclusively understood, as multiple interdependent parameters affect the OER activity simultaneously. Herein, a layered cobalt borophosphate precatalyst, Co(H 2 O) 2 [B 2 P 2 O 8 (OH) 2 ]·H 2 O, is fully reconstructed into two different CoCat phases. In contrast to previous reports, this reconstruction is not initiated at the surface but at the electrode substrate to catalyst interface. Ex situ and in situ investigations of the two borophosphate derived CoCats, as well as the prominent CoP i and CoB i identify differences in the Tafel slope/range, buffer binding and content, long-range order, number of accessible edge sites, redox activity, and morphology. Considering and interconnecting these aspects together with proton mass-transport limitations, a comprehensive picture is provided explaining the different OER activities. The most decisive factors are the buffers used for reconstruction, the number of edge sites that are not inhibited by irreversibly bonded buffers, and the morphology. With this acquired knowledge, an optimized OER system is realized operating in near-neutral potassium borate medium at 1.62 ± 0.03 V RHE yielding 250 mA cm -2 at 65 °C for 1 month without degrading performance., (© 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

[Display omitted] • P/N co-doped cabocatalysts exhibit superior performance for PMS activation. • The edge sites enhance adsorption of PMS/TC and the subsequent electron transfer. • Electron transfer promoted by the catalyst is the dominant pathway. • The P/N edge structures are more stable than that dopped in inner planner. • The formation of P-N bond is not conducive to PMS activation. A controllable synthetic route of carbon nanosheets co-doped with phosphorus and nitrogen was developed by pyrolysis of a supermolecular aggregate of self-assembled melamine, phytic acid, and carbon sheet. The as-prepared catalyst has shown a substantially increased efficiency for peroxymonosulfate (PMS) activation in the degradation of tetracycline (TC). The roles of dopants and edge sites were systematically investigated by both experimental characterizations and theoretical simulations. Compared with the undoped catalyst, the P/N co-doped catalyst has substantially enhanced the adsorption of PMS/TC and the subsequent electron transfer process, which is recognized as the dominant nonradical mechanism. Consequently, an efficient catalytic activity was obtained for the degradation of TC as well as other pollutants even under high salinity (500 mM) and high concentration wastewater (500 ppm). This work not only presents a non-metallic carbocatalyst with high catalytic activity for extensive environmental remediation, but also provides new insights into the edge P/N co-doping effects on the electron-transfer dominated nonradical activation of PMS. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) was used to investigate O chemisorption on the edge sites of graphene doped with quaternary nitrogen (N-graphene). The location of the doped quaternary N within the graphene cluster was systematically varied to determine the effect of interior versus edge doping on the reactivity of the edge graphene sites. Model 1b, where a quaternary-N atom is at the zigzag edge of the graphene cluster, is found to be the most favored structure and strongly adsorbs O molecule via a 'two feet' geometry. For this most stable O binding configuration, the potential-dependent free energy of reaction for the subsequent oxygen reduction reaction (ORR) steps was evaluated. The favored four electron-proton transfer mechanism passes through a dissociative O*+OH* state instead of an OOH* intermediate, followed by a series of reduction steps to produce water. At the equilibrium potential for ORR of 1.23 V-NHE, the protonation of O* and OH* both show uphill steps, but the production of O* is facile with a small overpotential. An applied potential of −0.15 V-NHE is required to facilitate the protonation of OH* to water, a larger overpotential than observed experimentally. While solvent effects may reduce this overpotential, our results suggest that the edge of the N-graphene is very active towards activation of O and production of O* and OH* but because of strong binding of the oxygen atom, the subsequent steps of the ORR reaction will be hindered. Mechanisms that have OH* formed at the edge site and then move to adjacent sites for more facile protonation will have to be explored in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • The origin of the electrocatalytic property of multiwalled carbon nanotubes (CNT) towards Vitamin D 3 oxidation is explored. • The performance of as grown CNT, air oxidized CNT, and CNTs subjected to different acid treatments towards Vitamin D 3 oxidation is compared. • The occluded metal catalyst particles and carbonaceous impurities in the MWCNTs do not influence its electrochemistry towards Vitamin D 3. • The oxygen functional groups present on the carbon nanotubes influence the electrochemistry significantly. Multiwalled carbon nanotubes (MWCNT) have been reported to be electrocatalytic towards a wide range of analytes. However, the electrocatalytic property is often wrongly attributed, and its origin is often due to the impurities included in the carbon nanotubes. The present report systematically explores the origin of the electrocatalytic nature of multiwalled carbon nanotubes towards Vitamin D 3 oxidation. It was found that, in addition to the edge sites, the oxygen functional groups present on the MWCNTs play a vital role in the electro-oxidation of Vitamin D 3. The analytical parameters obtained using MWCNT modified electrodes for Vitamin D 3 sensing are also presented. [ABSTRACT FROM AUTHOR]

Abstract: The selective hydrodesulfurization (HDS) of FCC gasoline is a key catalytic process for reducing sulfur content in gasoline. In addition, 5.75% of the European fuels used for transportation will have to incorporate biofuels, which implies that gasoline hydrotreatment will treat feeds containing various oxygenated compounds including by-products such as CO, CO2 or H2O. In the present work, we focus on the effect of CO partial pressure on the transformation of a model FCC gasoline composed of 2-methylthiophene (2MT) and 2,3-dimethylbut-2-ene (23DMB2N) molecules, over a alumina supported CoMoS catalyst. A negative and reversible impact of carbon monoxide on the conversion of 2MT and 23DMB2N is found. Moreover, the hydrodesulfurization (HDS) of 2MT alone is much more inhibited (30%) than hydrogenation (HYD) of 23DMB2N alone (10%). In contrast, when considering the model feed where 23DMB2N and 2MT are mixed together, the loss of HDS and HYD activities is comparable whatever the CO partial pressure. Density functional theory (DFT) calculations of CO adsorption on the S- and M-edge sites of the CoMoS particles show that CO adsorption is strongly favored with respect to olefin and 2MT adsorption on both types of sites, which explains its strong inhibiting effect on HYD and HDS. A rational explanation of the different inhibiting effects of CO observed on model molecules alone and model feed is proposed in correlation with the nature of the active S- and M-edge sites present on the hexagonal CoMoS particles and involved either in HDS or in HYD reactions. [Copyright &y& Elsevier]

Abstract: Reaction network analysis of the oxidative dehydrogenation (ODH) reaction of isobutane over model carbon catalysts with tailored open-edge graphitic structure and quinone-type oxygenated functionalities was used to identify the selective pathways for the formation of isobutene. Carbon-based materials have been widely used in catalysis, but the active sites are not well-understood due to the complexity of the carbon structure. Correct identification of these sites is essential for learning how to manipulate material structure to achieve high catalytic yields of the desired products. In this study, we created model catalysts with controllable surface concentration of oxygen based on graphitized mesoporous carbon (GMC). Our studies reveal that the ODH reaction of isobutane on carbon catalysts is a parallel-consecutive pathway with partial oxidative dehydrogenation for the formation of isobutene and deep oxidation pathway for the direct formation of CO and CO2 from isobutane. These two pathways show different dependence on the quinone-type oxygen sites: the rate constant leading to the desired partial oxidation product does not show a strong correlation to the density of the oxygen sites, whereas the rate constant leading to the unselective CO x products increases continuously with the density of oxygen sites. [Copyright &y& Elsevier]

Abstract: Carbon deposits originated from side organic reactions are known to strongly affect the performance of metal catalysts. Quite unexpectedly, the C atoms have been recently found to act favorably and to lead to the enhancement of the catalyst performance. In the present work we employ a density-functional method to uncover atomistic mechanisms of the very first step of modifying Pd nanoparticles by subsurface C. In the interior of Pd(111) facets C is most stable in octahedral subsurface sites; occupation of tetrahedral subsurface sites by adsorbed C atoms results in smaller stabilization. There, the surface-to-subsurface diffusion of C features distinctive activation barriers. However, near nanoparticle edges, where CH x decomposition precursors of C tend to be located, more mobile low-coordinated Pd atoms make the diffusion into tetrahedral subsurface sites almost non-activated. This peculiar “nano”-effect suggests that the initial low-temperature modification of Pd particles by atomic C is governed by a fast occupation of tetrahedral subsurface sites at edges, which therefore serve as a gate to the subsurface. [Copyright &y& Elsevier]

[Display omitted] • Edge-rich GFe 2 O 3 composite was prepared by an in situ thermal decomposition route. • Numerous edge sites endow the GFe 2 O 3 composite with accelerated kinetics. • GFe 2 O 3 composite exhibits an impressive rate capability of 822 mAh g−1 at 5 A g−1. • GFe 2 O 3 composite shows high Na+ storage capacity of 253 mAh g−1 at 2 A g−1. Iron oxides have been recognized as a potential electrode material for lithium-ion and sodium-ion batteries owing to their relatively ultrahigh theoretical capacity, low-cost and earth-rich resources. Nevertheless, the rapid capacity degradation and sluggish kinetics seriously limit their practical applications. Herein, the kinetics enhanced ultrafine Fe 2 O 3 nanocrystals (~5 nm) well anchored on graphene are prepared for high-rate lithium and sodium storage. The unique structure could provide abundant electrochemical active edge sites, short ion/electron diffusion pathways, and excellent electrical conductivity, allowing for enhanced electron/ion transport/diffusion kinetics. The fabricated Fe 2 O 3 /reduced graphene oxide nanocomposite shows impressive discharge capacity (1175 mAh g−1 at 0.2 A g−1), significant rate performance (822 mAh g−1 at 5 A g−1) and stable long-term cycle durability (993 mAh g−1 after 500 cycles at 1 A g−1) as a lithium-ion battery anode. As for sodium-ion storage, it also shows high discharge capacity of 701 mAh g−1 at 0.1 A g−1 and remarkable rate performance (253 mAh g−1 at 2 A g−1). These above intriguing electrochemical performances outperform most of the so-far recorded Fe 2 O 3 based electrodes. Such material design strategy may pave a new way for the development of outstanding performance anode materials based on earth-rich materials for energy storage application. [ABSTRACT FROM AUTHOR]