Search

Single-atom catalysts (SACs) based on metal–nitrogen–carbon (M–N–C) compounds have been identified as a potential substitute for Pt-based oxygen reduction reaction (ORR) catalysts due to their facile availability and low cost. M1M2–N–C based dual-atom catalysts (DACs) may be utilised to regulate the active site and optimise their ORR activity. Accordingly, M1M2–N6–C14 (M1 = Mn, Fe, Co; M2 = late transition metals) DACs were constructed within a graphene slab. M1M2–N–C is more stable than the corresponding M1–N–C and M2–N–C due to the affinity between M1 and M2. Furthermore, the ORR activity of FeM–N–C (M = late transition metals), MnM–N–C (Co, Ru, Rh, Os, Ir, and Re) and CoM–N–C (M = Cu, Zn, Pd, and Pt) is enhanced in comparison to that of Fe–N–C, due to the modified electronic properties. In comparison to other active ORR electrocatalysts, FeCu–N–C is positioned at a relatively high level on the volcano plot. To gain further insight into the dynamic stability of FeCu–N–C under working conditions (*OOH, 80 °C), an ab initio molecular dynamics simulation was employed. The accelerated structural evolution of the FeCu–N–C electrocatalyst resulted in the Cu atom being pulled out of the N–C substrate plane. Nevertheless, the resulting Fe(vacancy)–N–C and Fe(vacancy)–NH–C electrocatalysts have been observed to retain high ORR activity and stability. The findings of this study have significant implications for the design of DACs. [ABSTRACT FROM AUTHOR]

Novel exohedral metalloborospherenes Al12Li20&B60 and Al20Li12&B60 with the classical fullerene-like borospherene B60 were theoretically predicted and their structures and properties were studied. Incredibly, the B60 cage (pull electron oxidizer) pulls 50 and 60e− from exohedral metal atoms, forming two super-reduced polyanionic states B6050− and B6060−, respectively. Next, the two super-reduced polyanionic states (push electron oxidizers) owing to their negative electric fields push out the remaining valence electrons of exohedral metal atoms. Accordingly, the metalloborospherenes convert to electride salt molecules 6e−&[(Al3+)12(Li+)20]&B6050− and 12e−&[(Al3+)20(Li+)12]&B6060− due to the pull–push electron oxidation relay. It is known that the loss of electrons by the reducing agent results in an oxidation effect. The mechanism of losing electrons involves not only the pull electron but also the push electron, which results in push electron oxidation. As long as there is enough reducing agents in oxidation–reduction electride systems, the unusual pull–push electron oxidation relay will occur, showing new physical insights. More interestingly, the B60x− (x = 50 or 60) polyanions can also display push electron oxidation for embedded calcium atoms, forming endohedral spherical electride molecules 14e−&[(Al3+)12(Li+)20]&[(Ca6)8+@B6050−] and 22e−&[(Al3+)20(Li+)12]&[(Ca6)10+@B6060−], in which the supernormal pull–push–push electron oxidizing ability of the B60 cage is reflected in the total number of pull–push electrons up to 64 and 82, respectively. Remarkably, these spherical electride molecules have extraordinarily small multiple ionization potential (VIPn, n = 1–22) values, demonstrating a nuclear large-scale effect of the superatomic model on VIPn. [ABSTRACT FROM AUTHOR]

Triggering rapid reconstruction reactions holds the potential to approach the theoretical limits of the oxygen evolution reaction (OER), and spin state manipulation has shown great promise in this regard. In this study, the transition of Fe spin states from low to high was successfully achieved by adjusting the surface electronic structure of pentlandite. In situ characterization and kinetic simulations confirmed that the high‐spin state of Fe promoted the accumulation of OH− on the surface and accelerated electron transfer, thereby enhancing the kinetics of the reconstruction reaction. Furthermore, theoretical calculations revealed that the lower d‐band center of high‐spin Fe optimized the adsorption of active intermediates, thereby enhancing the reconstruction kinetics. Remarkably, pentlandites with high‐spin Fe exhibited ultra‐low overpotential (245 mV @ 10 mA cm−2) and excellent stability. These findings provided new insights for the design and fabrication of highly active OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Triggering rapid reconstruction reactions holds the potential to approach the theoretical limits of the oxygen evolution reaction (OER), and spin state manipulation has shown great promise in this regard. In this study, the transition of Fe spin states from low to high was successfully achieved by adjusting the surface electronic structure of pentlandite. In situ characterization and kinetic simulations confirmed that the high‐spin state of Fe promoted the accumulation of OH− on the surface and accelerated electron transfer, thereby enhancing the kinetics of the reconstruction reaction. Furthermore, theoretical calculations revealed that the lower d‐band center of high‐spin Fe optimized the adsorption of active intermediates, thereby enhancing the reconstruction kinetics. Remarkably, pentlandites with high‐spin Fe exhibited ultra‐low overpotential (245 mV @ 10 mA cm−2) and excellent stability. These findings provided new insights for the design and fabrication of highly active OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion hybrid supercapacitors (ZHSs) are promising energy storage devices owing to their high energy and power density. However, the selection of the voltage window to achieve the balance between energy density and cycling stability is still difficult. Herein, the protective effect of by-products deposited on the surface structure of the cathode material was studied based on the differences in the cycling stability of ultrathin carbon materials (UTCs) at different voltage windows. Through the calculation of the Gibbs free energy of the hydrogen evolution reaction (HER) process, the association of cathode by-products with voltage windows was described and confirmed for the first time: whether the by-product layer on the surface of the cathode material is broken or not can be considered a criterion for selecting the voltage window. Based on this, a flat pouch cell was fabricated in a wide voltage window of 0–1.9 V and exhibited an extremely high energy density of 267.9 W h kg−1 coupled with good flexibility and long cycle life with a capacity retention of 90.0% after 3000 cycles. Overall, this work introduces the relationship between cathode by-products and voltage windows for the first time, useful for providing more specific criteria for the selection of voltage windows. [ABSTRACT FROM AUTHOR]

High-entropy perovskite fluorides are very promising for the electrocatalytic oxygen evolution reaction (OER). However, the low kinetics of reconstruction reactions restrict their high catalytic activity. Herein, a novel strategy was developed for the modification of the surface K(CoMnFeNiCr)F3 (HEPF) using the electron-donating group pyrrolidone, for the first time, to promote the rate of reconstruction reactions. The experimental results and theoretical calculations demonstrated that after HEPF modification, the energy barrier for OH− adsorption was reduced to −5.37 eV. The surface modification with HEPF also enhanced the intrinsic conductivity owing to the improved band structure. This resulted in the formation of highly active catalytic species at lower potentials, leading to superior intrinsic catalytic activity. The optimized electrocatalyst exhibited an overpotential of only 242 mV at 10 mA cm−2, representing the best-reported value among similar materials. Overall, the proposed strategy looks promising for unlocking the excellent catalytic activity of high-entropy perovskite fluorides, useful for future syntheses of OER catalysts. [ABSTRACT FROM AUTHOR]

Phosphoric acid-doped polybenzimidazole (PA-doped PBI) membranes enable high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) to operate at elevated temperature (140–180 °C), with the advantages of simplified water/heat management. However, the relatively long start-up time and insufficient performance due to the introduction of the liquid phosphoric acid electrolyte are still major barriers to the application of HT-PEMFCs. Herein, a series of alkyl-substituted poly(arylene piperidinium) membranes are designed to modulate the content and distribution of phosphoric acid, which significantly reduces the ohmic and mass transfer resistance and boosts the performance of HT-PEMFCs in a wide operational temperature range. By tailoring the pendant alkyl groups of the piperidinium cations, the steric hindrance around the piperidinium cations and the free volume of poly(arylene piperidinium) can be well regulated. The optimized isobutyl-substituted poly(arylene piperidinium) membrane shows a high acid doping level (10.05) and a relatively high proton conductivity. As a result, a PEMFC based on this membrane shows significantly low ohmic and mass transfer resistances, consequently enhancing the peak power density of the HT-PEMFC to >1.5 W cm−2 at a moderate temperature of 120 °C under H2/O2 conditions. [ABSTRACT FROM AUTHOR]

The electrochemical decomposition of water plays a critical role in green and sustainable energy. However, the development of efficient and low-cost non-noble metal catalysts to overcome the high potential of the anodic oxygen evolution reaction (OER) is still challenging. In this work, electrocatalysts with high OER activity were obtained by doping Co/Fe bimetals into Ni3S2 (CF-NS) via a simple single-step hydrothermal method by adjusting the doping ratio of bimetals. A series of characterization studies revealed that the introduction of a Co/Fe co-dopant increased the number of active sites and improved the electroconductibility, while optimizing the electronic structure of Ni3S2. Meanwhile, Fe-induced high valence Ni contributed to the production of an OER active phase NiOOH. The unique dendritic crystal morphology facilitated the disclosure of the active sites and the expansion of mass transfer channels. The optimized sample required a low overpotential of 146 mV to obtain a current density of 10 mA cm−2 in 1.0 M KOH solution. The optimized sample also operated stably for at least 86 h. In sum, the proposed method looks very promising for designing efficient, stable, and low-cost non-precious metal catalysts with high conductivity and multiple active sites, useful for future synthesis of transition metal sulfide catalysts. [ABSTRACT FROM AUTHOR]

Vacancy engineering plays a significant role in the rational design of electrochemical energy conversion and storage. However, limited by traditional strategies, controllably introducing abundant vacancies remains challenging. Herein, a new strategy for controllable modulation of vacancy content by regulating the number of hydrogen bonds based on nickel fluoride alkoxide precursors (denoted as F–Ni–Ox–Ry) is proposed. The hydrogen bonds are formed by micro-design of the carbon chain structure to stabilize F ions on the surface during the synthesis process. Afterward, their breakage during electrochemical reconstruction processes leads to the overall release of F ions to generate vacancies. The adjustment of the carbon chain length can effectively control the number of hydrogen bonds, further microregulating the number of vacancies. The unique microstructural design yields a reconstructed nickel fluoride alkoxide (F–Ni–O2–R2) electrode with an ultra-high specific capacitance of 2975 F g−1 at a current density of 1 A g−1. This work not only provides a new strategy for the controllable modulation of vacancy engineering, but also a new perspective for the construction of novel energy storage electrodes by incorporating organic ligands into inorganic systems. [ABSTRACT FROM AUTHOR]

For a new challenge of stabilizing a classical fullerene-like borospherene composed of five- and six-membered rings, we take the lead to theoretically present a novel exohedral metalloborospherene Mg12Li8&B36 molecule (D6h). It features 12 η5(pentahapto)-Mg atoms and 8 η6-Li atoms capping 12 pentagonal faces and 8 hexagonal faces of classical fullerene-like borospherene D6h B36, respectively. Due to the pull-push electron transfer relay, the molecule is converted to an electride molecule (Mg2+)12(Li+)8&B3630− + 2e− with two excess electrons and an extraordinary high-valent B3630− polyanion with a full-shell electronic configuration, performing the stabilization of the classical fullerene-like B36 cage. As further findings emerge from this study, both the (Mg12Li8&B36)2+ cation (D6h) and the Mg12Li6&B36 salt (D6h) have higher stability than electride Mg12Li8&B36. Furthermore, embedding a metal atom pair in the boron cage of Mg12Li8&B36 leads to new endohedral electride molecules (Mg2+)12(Li+)8&(Mn+2@B3630−) + (2 + 2n) e− (M = Li, n = 1 and Be, n = 2). The embedded metal atom pair plays a prominent role in adding excess electrons. Notably, the Mg12Li8&B36 electride molecule can serve as both electron donor and electron acceptor and consequently acts as an electron reservoir. Encouragingly, Mg12Li8&B36 and its endohedral derivatives can be used as efficient external electric field manipulated second-order nonlinear optical (NLO) switches with high sensitivity and reversibility. In this sense, embedding a metal atom pair in the B36 cage provides a new strategy to manipulate NLO switching. [ABSTRACT FROM AUTHOR]

The devise and fabrication of highly efficient electrocatalysts have momentous practical significance for the development of future hydrogen energy systems. However, their potential uses in support construction are not well studied. In this work, a highly efficient electrocatalyst is developed for the hydrogen evolution reaction by anchoring single Pt atoms and clusters into functional amorphous pentlandite Fe5Ni4S8 (or FNS) to yield Pt–FNS composites. Amorphous FNS still provides great conductivity to the composites, thereby promoting rapid charge transfer. The presence of abundant defects in Pt–FNS composite catalysts induces pleasant atomic dispersion and anchoring of Pt species. In addition, the formation of single Pt atoms combined with clusters and low‐Pt‐loading improves the utilization of Pt and reduces the cost. The turnover frequency analysis suggests Pt–FNS systems possess significant unit catalytic activity. The synergetic catalytic effect issued from high conductivity, abundant active sites and elevated intrinsic activity forms Pt–FNS systems with efficient pH‐universal catalytic activity. The systems exhibit low overpotentials of only 30, 65, and 98 mV at 10 mA cm−2 under acidic, alkaline, and neutral conditions, respectively. In sum, the proposed route looks promising for the fabrication of new electrocatalysts with improved properties. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) that occurs on the outermost layer of electrocatalysts is significantly affected by the composition and structure of the electrocatalysts. During the preparation of PtM alloy electrocatalysts, high-temperature annealing in an inert or reducing atmosphere could promote the segregation of M toward the core, forming a highly active Pt-skin structure. However, under fuel cell operating conditions, the adsorption of oxygen-containing groups could stimulate the easily dissolved M to segregate to the surface, reducing the activity and stability of the electrocatalysts. In this work, we conducted segregation energy calculation of PtM (M = Cu, Pd, Au) electrocatalysts under specific adsorption (SA), aqueous solution (AS) and an external electric field (EEF) with a density functional theory method. It was found that different factors have different effects on the segregation energy: ΔΔESA ≫; ΔΔEEEF > ΔΔEAS. The coupling effects have also been considered and compared: ΔΔESA+EEF > ΔΔESA+AS > ΔΔEEEF+AS. When including all three factors, the change of segregation energy could reach 1.63 eV. Therefore, operating conditions have a noteworthy influence on the segregation behavior of PtM ORR electrocatalysts, which should be considered in the further design of PtM ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Iron‐nitrogen‐doped carbon (Fe‐NC) is an ideal candidate to replace Pt‐based oxygen reduction reaction (ORR) electrocatalysts due to its low cost and comparably high intrinsic activity. To further enhance the ORR performance of Fe‐NC electrocatalysts, efforts have been focused on two main methods. One is to enhance the intrinsic activity of FeNx sites through electronic and geometric regulation, and the other is to increase the density of active sites by introducing high‐nitrogen‐containing precursors or co‐doping methods. Herein, we report a strategy to further increase the Fe loading through the introduction of a trace amount of Cu atoms. Significant enhancement of the electrocatalytic ORR property is observed in the as‐prepared Fe and Cu co‐doped electrocatalyst with superior half‐wave potential (E1/2) in both alkaline and acid electrolyte. Experimental and theoretical study reveals that the introduction of a trace amount of Cu atoms is beneficial for the formation of FeN4 sites, owing to the reduced formation energy. This work opens up a wide avenue to further increase the Fe loading in Fe‐NC electrocatalysts through bimetal co‐doping method. [ABSTRACT FROM AUTHOR]

The strain effect on oxygen reduction reaction (ORR) activity and stability of FeNC electrocatalysts has been studied using density functional theory in this work. Based on the reaction free energy results, the rate-determining step (RDS) of ORR on FeNC is *OH → H2O, and the reaction proceeds with the pathway O2 → *OOH → *O → *OH → H2O on the Fe site. Tensile stress is favorable to enhance the ORR activity, and the highest ORR activity is obtained on the 6%-FeNC electrocatalyst. On the other hand, when the whole oxygen reduction process needs synergy between Fe and adjacent C atoms and proceeds with the pathway O2 → *OOH → *TS → *O & #OH → *O → *OH → H2O, the applied stress will decrease the ORR activity of the FeNC electrocatalyst. We further constructed a Cu@FeNC core–shell model to simulate strained FeNC. However, the adsorption energy of ORR intermediates on Cu@FeNC (1.9%-FeNC) is much weaker than on the corresponding 2%-FeNC, mainly due to the coordination between the Cu substrate and Fe atom. In addition, the formation energy and binding energy indicate that neither tensile nor compressive stress is conducive to the stability of the FeNC electrocatalyst. In summary, tensile stress could enhance the ORR activity of FeNC electrocatalysts when ORR occurs on the Fe atom only. What's more, we should pay more attention to the influence of interface interaction if utilizing a M@FeNC model to achieve strained FeNC. [ABSTRACT FROM AUTHOR]

BACKGROUND: Titanium dioxide (TiO2) is considered as one of the most potential photocatalysts among various oxide semiconductor photocatalysts. In order to improve the photocatalytic performance of TiO2‐based photocatalysts, it is pivotal to explore an efficient method to promote the separation of photoexcited charges, accelerate the carrier transmission efficiency and enhance visible‐light absorption. RESULTS: In this study, heterostructured Ag/g‐C3N4/TiO2 ternary photocatalysts were successfully constructed using a facile accessible route. The structures, morphologies, chemical compositions and optical properties of the obtained composites were characterized by various analytical methods. The performance of the ternary photocatalysts was then tested for degradation of Rhodamine B (RhB) under visible light irradiation. The specimen prepared by loading 2% silver (Ag) nanoparticles onto the composites showed the best photocatalytic activity towards RhB degradation (99.7%) with satisfactory stability. The degradation rate using ternary photocatalyst reached 0.0179 min−1, almost 20‐ and 2.3‐folds higher than those of pure TiO2 and binary sample. To gain better insights, a possible photocatalytic enhancement mechanism was also proposed. CONCLUSION: The improved photocatalytic properties were attributed to the heterostructure between TiO2 and graphite carbon nitride (g‐C3N4) as well as the loading Ag nanoparticles. The formation of the heterostructure between TiO2 and g‐C3N4, combined with the load of Ag nanoparticles created a synergistic effect, leading to the enhanced photocatalytic performance. Overall, these findings look promising for future photodegradation of organic pollutants. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) plays a critical role in efficient conversion and storage of renewable energy sources, whereas the active sites for the most representative electrocatalysts, Ni–Fe compounds, remain under debate. In this work, we have developed polymeric carbon nitride (PCN) with atomically dispersed N-coordinated Ni–Fe sites to investigate the OER process. The Ni–Fe dual sites consist of adjacent Ni and Fe atoms coordinated with N atoms in the PCN matrix. NiFe-codoped PCN exhibits higher electrocatalytic activity than monometal-doped catalysts, showing a lower overpotential (310 mV at 10 mA cm−2) and smaller Tafel slope (38 mV dec−1) in 1 M KOH, indicating that Ni–Fe dual-metal sites significantly favor the OER process. According to density functional theory calculations based on the oxidized-NiFe@PCN model, it was found that adjacent Ni and Fe atoms co-participate in the OER process for NiFe-codoped PCN, leading to a much lower energy barrier (0.10 or 0.22 eV for U = 1.58 V), while the effect of electronic modification of the single metal active sites by the other component (Ni sites by Fe sites or vice versa) contributes less to activity enhancement, thus leading to a rational explanation on the synergistic effect of the NiFe-based OER catalysts. [ABSTRACT FROM AUTHOR]

Introducing heteroatoms into two-dimensional nanosheets was revealed to be a quite promising strategy to tune their electronic and magnetic properties as well as chemical reactivity, thus greatly widening their application fields. Herein, by means of density functional theory (DFT) computations, we have systematically investigated the electronic and magnetic properties as well as chemical reactivity of MoS2 nanosheets doped with several common nonmetal dopants (B, C, N, O, and P). Our results revealed that these nonmetal atoms can be strongly captured by the S vacancy of the MoS2 nanosheet, ensuring their high stability. Compared with the pristine MoS2 nanosheet, these doped MoS2 systems exhibit decreased band gaps due to the introduction of impurity levels. In particular, the adsorption of gas molecules on the MoS2 monolayer can be enhanced to different degrees after nonmetal doping, suggesting great potential for developing gas sensors or catalysts. Thus, by carefully choosing the nonmetal atoms, the inert basal plane of a MoS2 nanosheet can be effectively activated for various applications. [ABSTRACT FROM AUTHOR]

With the approaching commercialization of proton exchange membrane fuel cell technology, developing active, non-precious metal oxygen reduction reaction (ORR) catalyst materials to replace currently used Pt-based catalysts is a necessary and essential requirement in order to reduce the overall system cost. Here, we report a single-atom doped molybdenum disulfide sheet (short as X-MoS2) catalyst for the ORR using a dispersion-corrected density functional theory method. Of all the eleven X-MoS2 (X = B, C, N, O; Al, Si, P; Ga, Ge, As, and Se) systems, only the phosphorus atom doped molybdenum disulfide (P-MoS2) has an O2 adsorption energy close to that of a Pt(111) surface. We have further explored the detailed ORR mechanism of P-MoS2. Along the four-electron reaction pathway, the reduction of OH to H2O is the rate-limiting step with the largest diffusion barrier of 0.79 eV. [ABSTRACT FROM AUTHOR]

The synthesis of ultrathin noble-metal-based alloy nanosheets with few-atomic-layer thickness remains a great challenge although they have attracted remarkable attention. Herein, ultrathin wrinkle-free Pd4Cu1 nanosheets with lateral size of 33.8 nm and thickness of 2.71 nm were successfully prepared using n-butylamine as a bifunctional agent. The ingenious structure possesses the highest electrochemically active surface area among the reported PdCu nanostructures. The quantum confinement and entrapment effects of the Pd4Cu1 nanosheets render the modulation of d-band electrons and weaken the adsorption of poisoning species, thus enhancing the performance towards methanol oxidation. The mass activity of the ultrathin wrinkle-free Pd4Cu1 nanosheets was 6.7-times and 4.8-times higher than that of commercial Pd black and Pt black, respectively. This study highlights the important role of designing ultrathin alloy nanosheets towards enhancing electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Mild annealing enables inactive nitrogen (N)-doped amorphous carbon (a-C) films abundant with chaotic bonds prepared by magnetron sputtering to become effective for the oxygen reduction reaction (ORR) by virtue of generating pyridinic N. The rhythmic variation of ORR activity elaborates well on the subtle evolution of the amorphous C−N bonds conferred by spectroscopic analysis. [ABSTRACT FROM AUTHOR]

In this work, the adsorption of Rhodamine 6G molecules on some graphene substrates is investigated using density functional theory. Some simple models, such as those of perfect graphene, defective graphene, *O/*OH modified graphene and B/N doping graphene, are constructed as substrates to simulate graphene oxide and B/N doping graphene sheets. It is demonstrated that the interactions of Rhodamine 6G molecules with graphene materials are strong. In particular, the amine group of Rhodamine 6G molecules can favor the formation of a chemical bond with some graphene substrates characterized by under-coordinated atoms. The chemical interactions would lead to significant changes in the electronic structures of graphene substrates, which have the potential to tune the electronic properties of graphene. In addition, our calculations predict that the epoxy/hydroxyl group attached to the surface of graphene could be removed by Rhodamine 6G molecules, which suggests that the reduction reaction may occur in graphene oxide upon Rhodamine 6G doping. The surface plasmon resonance spectra of R6G adsorbed on some graphene substrates are also characterized, which are well in agreement with some computational results. Therefore, combined with experimental observations, our results provide an insight into the interaction of Rhodamine 6G molecules with graphene materials. [ABSTRACT FROM AUTHOR]

Outstanding hydrogen evolution reaction (HER) activity and stability are highly desired for transition metal dichalcogenide (TMD)-based catalysts as Pt substitutes. Here, we theoretically calculated and experimentally showed that adsorbing Pd atoms on the basal plane of defect-rich (DR) MoS2 will effectively modulate the surface electronic state of MoS2 while retaining its active sites, which greatly enhanced the HER activity. Three decoration strategies were used to implement this design: direct epitaxial growth, assembling spherical nanoparticles and assembling Pd nanodisks (NDs). The results showed that only Pd NDs are able to be site-specifically decorated on the basal plane of DR-MoS2 through lamellar-counterpart-induced van der Waals pre-combination and covalent bonding. This Pd ND/DR-MoS2 heterostructure exhibits exceptional Pt-similar HER properties with a low onset-overpotential (40 mV), small Tafel slope (41 mV dec−1), extremely high exchange current density (426.58 μA cm−2) and robust HER durability. These results demonstrate a novel modification strategy by a lamellar metallic nanostructure for designing excellent layered TMD-based HER catalysts. [ABSTRACT FROM AUTHOR]

The structural and electronic properties of zigzag MoS2 nanoribbons are investigated using first-principles density functional theory. Our models are motivated by the experimental observations, in which both Mo edges are terminated by S atoms. Our calculations show that the edge can introduce some extra states into the energy gap, which lead nanoribbons to exhibit a metallic characteristic. Such extra states around the Fermi level are flat or dispersed. Through detailed analyses, we identify and discriminate them based on the major contributors. By applying an external transverse electric field, Eext the extra states around the Fermi level can shift apparently, especially for those attributed to Mo-edge atoms. It can be explained by the charge redistribution in the MoS2 nanoribbons due to Eext. In addition, the nanoribbon can be changed from metal to an n/p-type semiconductor according to different edge hydrogenation. After full edge hydrogenation, we observe a characteristic of anti-bonding orbitals between H and S atoms at the Mo-edge. Interestingly, the energy of anti-bonding orbitals and electric conductivity of nanoribbons can be tailored by Eext. The results suggest a strategy controlling the performance of MoS2 for hydrogen evolution. [ABSTRACT FROM AUTHOR]

In this work, the systems are constructed with the defect lines of B–B or N–N dimers embedded in a graphene matrix using density functional theory. It is found that the Dirac-cone dispersions appear at the Fermi level in the bands introduced by the B or N heteroatom, linear B–B or N–N dimers, demonstrating that the carrier mobility is ∼106 m s−1 which is comparable with that of the pristine graphene. Most importantly, such dimer lines act as the quasi-1-D conducting nanowires whose charge carriers are confined around the linear defects in these dimers while the charge carriers in pristine graphene are dispersed two-dimensionally. Such systems suggest that heteroatoms in graphene can indeed contribute to the Dirac cone. In addition, the type of carriers (p-type or n-type) can be manipulated using the B or N heteroatoms, respectively. This will greatly enrich the electronic properties of Dirac semimetals. [ABSTRACT FROM AUTHOR]

The stability is one of the key requirements for commercializing the fuel cell electrocatalysts in automotive applications. For the widely used Pt-based catalysts, it can be achieved by the formation of a stable Pt skin on the surface. Here, we employed density functional theory (DFT) to explore the stability of monolayer Pt (PtML) on various near surface alloy (NSAs) surfaces, PtML/MML/Pt(111) (M = Fe, Co, Ni, Cu; Ru, Rh, Pd, Ag; Os, Ir, Au), under various environmental conditions. Our results show that under the vacuum condition, the alloying M except Ag and Au thermodynamically prefer to stay in the subsurface and the formation of PtML on the surface is thermodynamically favored. A barrier has to be overcome for M to segregate. The situation varies under various electrochemical conditions. Depending on the solutions and the operating reaction pathway, different M should be considered for alloying with Pt to maintain the stability of surface PtML. PtRh and PtPd are the only two systems, where the surface PtML is likely to stay intact in perchloric acid (HClO4), sulfuric acid (H2SO4), phosphoric acid (H3PO4) and alkaline solutions as well as under the oxygen reduction reaction (ORR) conditions via different pathways. PtIr should also be paid attention, which falls only during the ORR via the OOH intermediate. Our results highlight the importance of chemical environments in affecting the stability of the catalysts. [ABSTRACT FROM AUTHOR]

Calculations have been made for single-walled zigzag ( n, 0) carbon nanotubes containing substitutional boron impurity atoms using ab initio density functional theory. It is found that the formation energies of these nanotubes depend on the tube diameter, as do the electronic properties, and show periodic feature that results from their different π bonding structures compared to those of perfect zigzag carbon nanotubes. When more boron atoms are incorporated into a single-walled zigzag carbon nanotube, the substitutional boron atoms tend to come together to form structure of BC3 nanodomains, and B-doped tubes have striking acceptor states above the top of the valence bands. For the structure of BC3, there are two kinds of configurations with different electronic structures. [ABSTRACT FROM AUTHOR]

The grand challenge in the development of atomically dispersed metallic catalysts is their low metal-atom loading density, uncontrollable localization and ambiguous interactions with supports, posing difficulty in maximizing their catalytic performance. Here, we achieve an interface catalyst consisting of atomic cobalt array covalently bound to distorted 1T MoS2 nanosheets (SA Co-D 1T MoS2). The phase of MoS2 transforming from 2H to D-1T, induced by strain from lattice mismatch and formation of Co-S covalent bond between Co and MoS2 during the assembly, is found to be essential to form the highly active single-atom array catalyst. SA Co-D 1T MoS2 achieves Pt-like activity toward HER and high long-term stability. Active-site blocking experiment together with density functional theory (DFT) calculations reveal that the superior catalytic behaviour is associated with an ensemble effect via the synergy of Co adatom and S of the D-1T MoS2 support by tuning hydrogen binding mode at the interface. While single-atom catalysis offers an efficient materials usage, the ambiguous interactions with supports poses a difficulty in understanding catalytic performances. Here, authors show an ensemble effect via synergy of Co adatoms and the S of MoS2 supports to boost hydrogen evolution activities. [ABSTRACT FROM AUTHOR]

In article number 1800391, Kan Zhang, Mao Wen, Shansheng Yu, and co‐workers present a one‐step manufacturing approach to obtain a hard yet hydrophobic surface based on TaN coating by doping Cu. The Cu2O on the surface have full Cu 3d shells, achieving a coordinative saturation, which can inhibit hydrogen bonding with interfacial water molecules, enhancing the hydrophobicity of TaN. [ABSTRACT FROM AUTHOR]

The hard yet hydrophobic surface capable of withstanding harsh conditions is needed in a broad range of applications. This combined computational‐experimental study exhibits an effective modification method for transition metal nitrides protective coatings toward both excellent mechanical and robust hydrophobic properties. It indicates that the introduction of low concentrations of Cu as the solute atoms substitute for the Ta atoms in TaN lattice can form the TaCuN solid solution structure. Meanwhile, the evolution of microstructure induces the refined grains and higher H/E*, which results in a combination of improved hardness and enhanced toughness. Better yet, a moderate incorporation of solute Cu atoms into TaN structure can induce a charge depletion state and form a Cu2O surface on TaN, as demonstrated by X‐ray photoelectron spectroscopy and electron density difference pattern. The Cu2O phase has an essentially full Cu 3d shell achieving the coordinative saturation, which can inhibit hydrogen bonding with interfacial water molecules, succeeded in enhancing the hydrophobicity of TaN. Density functional theory calculations are further employed to clarify that hydrophobic feature of Cu2O groups should be responsible for the tuning of wettability via destroying hydrogen‐bonding network of water molecules next to the surface. The hard yet hydrophobic surface is realized by one‐step manufacturing approach. The robust hydrophobic surfaces are got based on TaN coating by doping Cu via magnetron cosputtering. The Cu2O phase has an essentially full Cu 3d shell achieving the coordinative saturation, which can inhibit hydrogen bonding with interfacial water molecules, succeeded in enhancing the hydrophobicity of TaN. [ABSTRACT FROM AUTHOR]

The front cover artwork is provided by Prof. Wei Zhang and Cai Zhang from Jilin University (Changchun, China). The image shows that heat treatment can govern the bonding states and unlock the ORR activity for nitrogen-doped amorphous carbon, which is an analogy to the beauty of the stained-glass windows of Sagrada Família Basílica (Barcelona, Spain) revealed by the sunlight streaming through the windows. Read the full text of the Communication at . [ABSTRACT FROM AUTHOR]

The Front Cover picture is inspired by the principle demonstrated in the fascinating Sagrada Família Basilica (Barcelona, Spain), where sunlight streaming through the windows reveals the beauty of its stained‐glass windows. Similarly, in this work, thermal activation of the chemically inert amorphous carbon−nitrogen reveals its extraordinary oxygen reduction reaction activity! More information can be found in the Communication by W. Zhang, W. Zheng, and co‐workers on page 1269 in Issue 6, 2017 (DOI: 10.1002/celc.201700106). [ABSTRACT FROM AUTHOR]