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Single‐atom catalysts (SACs) exhibit intriguing performance in electrocatalysis owing to their maximized atom utilizations and unique electronic structures, but effective anchoring metal atoms with defined coordination structure on hierarchical integrated electrode remain a challenge. Herein, a fast and facial flame‐assisted strategy is developed to construct oxygen‐coordinated SACs on integrated carbon nanotube (CNT) arrays with promising applications in electrocatalysis. Density functional theory calculations show that oxygen in carbon substrate imparts homogeneous sites for the efficient anchoring of metal atoms, thereby enabling SACs to disperse uniformly and firmly and thus bringing optimized activities. Moreover, the integrated CNT array with abundant oxygen‐containing groups is constructed and has been used as an efficient matrix for anchoring metal atoms (CNT‐O@M) via a flame‐assisted method. The as‐prepared CNT‐O@M (M = Co and Pt as typical examples) shows excellent activities in electrocatalytic oxygen reduction reaction and hydrogen evolution reaction with utilization of active site as high as 75.7%, which is superior to the reported SACs. Particularly, the performance of CNT‐O@M can maintain stably under various harsh conditions, showing a promising prospect in the long‐time applications. The methodology and concept proposed in this work could be extended to the synthesis of a variety of integrated SACs for efficient electrocatalysis. [ABSTRACT FROM AUTHOR]

We constructed α-graphyne nanotubes (αGyNTs) and performed density functional theory calculations to investigate the electronic properties of zigzag and armchair αGyNTs. We found that all zigzag graphyne nanotubes (Z-αGyNTs) were semiconductors. In particular, the band gap of Z-αGyNTs showed an oscillatory dependence on tube size which could be further classified into three families with N z = 3 m − 1, 3 m and 3 m + 1 where m is a positive integer. This resulted in band gap magnitudes in the following rank order: 3 m − 1 > 3 m + 1 > 3 m. Armchair αGyNTs were also calculated to be semiconductor with very small band gaps when tube size is small, though they become metallic as the tube size increases. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were carried out to investigate how single-atom vacancies affect the electronic and magnetic properties of three types of graphyne model systems. Our simulations demonstrate that a single-atom vacancy can lead to an in-plane structural rearrangement, which plays an important role in tuning the electronic structures. A dispersionless spin-polarized band was observed around the fermi level, inducing strong magnetism in the three graphyne models. The single-atom vacancy can induce a 1.1–1.3 μ B magnetic moment into αGy and βGy, while this value increases significantly to about 1.8μ B for γGy. This single-atom vacancy technique is a promising method of manipulating the electronic and magnetic properties of graphyne. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were performed using a MPWB1K functional to interpret the charge transport (CT) properties of stacked annelated β-trithiophene molecules. The goal was to help understand how the chemical composition, face-to-face stacking, intra- and intermolecular correlations, and the applied electric field affect the CT properties of this organic semiconductor compared with those of the edge-to-face "herringbone" motif. The variations in the frontier molecular orbitals, energy gap, nonadiabatic electron attachment energies (EAE), and vertical detachment energies (VDE) were investigated under an external electric field as a function of the number of stacked layers (n). Two possible CT pathways, monomer-to-monomer (MM) and dimer-to-dimer (DD) transports, were postulated to determine the charge carrier conductivities of these molecules. The results highlight that the intermolecular electronic couplings and electrostatic interactions can significantly affect the stacking geometry, even in more extended structures; displaced stacks with smaller interlayer spacing resulted in more compact stacking and, thus, higher CT efficiency; face-to-face stacking geometries can help to reduce the energy gap and VDE. Despite the fact that common thiophene-based oligomers adopting edge-to-face herringbone motifs exhibited p-type (hole-transporting) characters, the face-to-face stacked models based on annelated β-trithiophenes exhibited remarkably increased n-type (electron-transporting) performances. The electric field in the z-direction produced a small influence on the DD charge transport, whereas both electron and hole mobilities decreased dramatically in the MM case. More importantly, in MM charge transport, the electric field increases the hole mobility so that it is higher than that of the electron. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were carried out to study how the position of single-atom doping affects the electronic properties of three graphyne models. We found that the position of the dopant (B, N, or O) plays an important role in tuning the electronic structure of graphynes. For α-graphyne, the electronic structure is significantly different for different positions of B and O doping. For β-graphyne, the electronic structure depends remarkably on the doping position for O doping, but not much for B and N doping, whereas for γ-graphyne, it depends on the position for B and O doping, but not for N doping. [ABSTRACT FROM AUTHOR]

Herein, we develop a free-standing trifunctional and durable electrocatalyst integrating the Re-doped Ni 3 S 2 nanoarray on N-doped graphene (NG) modified nickel foam substrate (Re–Ni 3 S 2 /NG/NF). Particularly, Re-doping is proven to modify the local electronic structure, increase the electroactive surface area, and optimize the adsorption energies of Ni 3 S 2 , greatly enhancing trifunctional activities. Accordingly, the water electrolyzer based on the symmetric Re–Ni 3 S 2 /NG/NF electrodes achieves a small cell voltage of 1.58 V at 10 mA cm−2 and high Faradaic efficiency of ∼97%, exceeding Pt/C + IrO 2 counterpart. Moreover, the rechargeable Zn–air battery with the Re–Ni 3 S 2 /NG/NF leads to achieve a high power density of 99 mW cm−2 and round-trip efficiency of 71.2% with a long term stability of 5000 cycles. Taking full potential of Re–Ni 3 S 2 /NG/NF electrocatalysts used as "all-in-one" electrode, a real-life operation of self-powered water splitting system is demonstrated for practical applications into highly efficient and multifunctional renewable energy systems. The Re-doped Ni 3 S 2 nanoarray is designed and integrated on N-doped graphene modified nickel foam substrate as an efficient and robust trifunctional electrocatalyst for both water splitting and rechargeable Zn–air battery. Experimental and theoretical analyses demonstrate that the Re doping endows the Re–Ni 3 S 2 modulated electronic structural configuration and optimized chemisorption energy toward intermediates, which synergistically boosts the trifunctional electrocatalytic activity. [Display omitted] • Re-doping induces the lattice distortion and surface deformation of Ni 3 S 2. • Re–Ni 3 S 2 /NG/NF exhibits excellent trifunctional activities for HER/OER/ORR. • The Re–Ni and Ni–Ni bridge, Re–Ni bridge, and NG are trifunctional active sites. • Re–Ni 3 S 2 /NG/NF serves as electrodes for both water electrolyzer and Zn–air battery. • Highly efficient Zn–air battery powered water splitting system is demonstrated. [ABSTRACT FROM AUTHOR]