Observing High‐Pressure Chemistry in Graphene Bubbles

Using IR spectroscopy, high‐pressure reactions of molecules were observed in liquids entrapped by graphene nanobubbles formed at the graphene–diamond interface. Nanobubbles formed on graphene as a result of thermally induced bonding of its edges with diamond are highly impermeable, thus providing a good sealing of solvents within. Owing to the optical transparency of graphene and diamond, high‐pressure chemical reactions within the bubbles can be probed with vibrational spectroscopy. By monitoring the conformational changes of pressure‐sensitive molecules, the pressure within the nanobubble can be calibrated as a function of temperature and it is about 1 GPa at 600 K. The polymerization of buckministerfullerene (C₆₀), which is symmetrically forbidden under ambient conditions, is observed to proceed in well‐defined stages in the pressurized nanobubbles.     

Large Hexagonal Bi‐ and Trilayer Graphene Single Crystals with Varied Interlayer Rotations

Bi‐ and trilayer graphene have attracted intensive interest due to their rich electronic and optical properties, which are dependent on interlayer rotations. However, the synthesis of high‐quality large‐size bi‐ and trilayer graphene single crystals still remains a challenge. Here, the synthesis of 100 μm pyramid‐like hexagonal bi‐ and trilayer graphene single‐crystal domains on Cu foils using chemical vapor deposition is reported. The as‐produced graphene domains show almost exclusively either 0° or 30° interlayer rotations. Raman spectroscopy, transmission electron microscopy, and Fourier‐transformed infrared spectroscopy were used to demonstrate that bilayer graphene domains with 0° interlayer stacking angles were Bernal stacked. Based on first‐principle calculations, it is proposed that rotations originate from the graphene nucleation at the Cu step, which explains the origin of the interlayer rotations and agrees well with the experimental observations.     

Facile Mechanochemical Synthesis of Nano SnO2/Graphene Composite from Coarse Metallic Sn and Graphite Oxide: An Outstanding Anode Material for Lithium‐Ion Batteries

A facile method for the large‐scale synthesis of SnO₂ nanocrystal/graphene composites by using coarse metallic Sn particles and cheap graphite oxide (GO) as raw materials is demonstrated. This method uses simple ball milling to realize a mechanochemical reaction between Sn particles and GO. After the reaction, the initial coarse Sn particles with sizes of 3–30 μm are converted to SnO₂ nanocrystals (approximately 4 nm) while GO is reduced to graphene. Composite with different grinding times (1 h 20 min, 2 h 20 min or 8 h 20 min, abbreviated to 1, 2 or 8 h below) and raw material ratios (Sn:GO, 1:2, 1:1, 2:1, w/w) are investigated by X‐ray diffraction, X‐ray photoelectron spectroscopy, field‐emission scanning electron microscopy and transmission electron microscopy. The as‐prepared SnO₂/graphene composite with a grinding time of 8 h and raw material ratio of 1:1 forms micrometer‐sized architected chips composed of composite sheets, and demonstrates a high tap density of 1.53 g cm^?3. By using such composites as anode material for LIBs, a high specific capacity of 891 mA h g^?1 is achieved even after 50 cycles at 100 mA g^?1.     

Solar Hydrogen from an Aqueous,Noble‐Metal‐Free Hybrid System in a Continuous‐Flow Sampling Reaction System

We introduce the visible‐light photocatalytic H₂ evolution reaction as catalyzed by a cobaloxime/carbon nitride (C₃N₄) noble‐metal‐free hybrid photosystem by using a continuous‐flow sampling reaction system. The photocatalytic H₂ evolution rate is highly dependent on the structure of C₃N₄, in which porous C₃N₄ shows the best activity compared with bulk C₃N₄ (lamellar) and C₃N₄ nanosheets. When using porous C₃N₄, the system is neither affected by the solution pH, nor the C₃N₄ concentration, nor the structure of the cobaloxime complex.     

Enhanced Thermal Oxidation Stability of Reduced Graphene Oxide by Nitrogen Doping

Nitrogen‐doped reduced graphene oxide (N‐doped RGO) samples with a high level of doping, up to 13 wt. %, have been prepared by annealing graphene oxide under a flow of pure ammonia. The presence of nitrogen within the structure of RGO induces a remarkable increase in the thermal stability against oxidation by air. The thermal stability is closely related with the temperature of synthesis and the nitrogen content. The combustion reaction of nitrogen in different coordination environments (pyridinic, pyrrolic, and graphitic) is analyzed against a graphene fragment (undoped) from a thermodynamic point of view. In agreement with the experimental observations, the combustion of undoped graphene turns out to be more spontaneous than when nitrogen atoms are present.     

Performance Enhancement of Bulk Heterojunction Solar Cells with Direct Growth of CdS‐Cluster‐Decorated Graphene Nanosheets

Two‐dimensional graphene–CdS (G–CdS) semiconductor hybrid nanosheets were synthesized in situ by graphene oxide (GO) quantum wells and a metal–xanthate precursor through a one‐step growth process. Incorporation of G–CdS nanosheets into a photoactive film consisting of poly[4,8‐bis‐(2‐ethyl‐hexyl‐thiophene‐5‐yl)‐benzo[1,2‐b:4,5‐b]dithiophene‐2,6‐diyl]‐alt‐[2‐(2‐ethyl‐hexanoyl)‐thieno[3,4‐b]thiophen‐4,6‐diyl] (PBDTTT‐C‐T) and [6,6]‐phenyl C₇₀ butyric acid methyl ester (PC₇₀BM) effectively decreases the exciton lifetime to accelerate exciton dissociation. More importantly, the decreasing energy levels of PBDTTT‐C‐T, PC₇₀BM, and G–CdS produces versatile heterojunction interfaces of PBDTTT‐C‐T:PC₇₀BM, PBDTTT‐C‐T:G–CdS, and PBDTTT‐C‐T:PC₇₀BM:G–CdS; this offers multi‐charge‐transfer channels for more efficient charge separation and transfer. The charge transfer in the blend film also depends on the G–CdS nanosheet loadings. In addition, G–CdS nanosheets improve light utilization and charge mobility in the photoactive layer. As a result, by incorporation of G–CdS nanosheets into the active layer, the power‐conversion efficiency of inverted solar cells based on PBDTTT‐C‐T and PC₇₁BM is improved from 6.0 % for a reference device without G–CdS nanosheets to 7.5 % for the device with 1.5wt % G–CdS nanosheets, due to the dramatically enhanced short‐circuit current. Combined with the advantageous mechanical properties of the PBDTTT‐C‐T:PC₇₀BM:G–CdS active layer, the novel CdS‐cluster‐decorated graphene hybrid nanomaterials provide a promising approach to improve the device performance.     

CH4, CO2和H2O在非金属原子修饰石墨烯表面的吸附

煤层气(矿井瓦斯)是一种有望替代传统化石燃料,如煤、石油和天然气的非常规气体. 作为可得的清洁能源,它的利用被认为是节能和经济的选择. 在本工作中,非金属原子X(X=H,O,N,S,P,Si,F,Cl)修饰的石墨烯(Gr)被用来代表具有结构异性的煤表面模型. 通过密度泛函理论系统地研究了煤层气组分Y(Y=CH₄,CO₂,H₂O)在非金属原子修饰石墨烯上的吸附作用. 结果表明Y在非金属原子修饰石墨烯上的吸附均为物理吸附. 态密度和差分电荷密度共同表明了这种弱的相互作用.其中,H和Cl对CH₄的作用较大; N、O、F、Cl对CO₂的作用较强; N,Cl对H₂O的影响不容忽视. 总的来说,吸附能大小依次为：H₂O>CO₂>CH₄. 因此,在CH₄富集的煤层里注入H₂O或CO₂可以与CH₄形成竞争吸附,进而提高煤层气采收率. 本工作提供了在分子水平下煤层气与非金属原子修饰石墨烯之间的相互作用的详情,并为煤层瓦斯的开采与分离提供了有用的信息.     

Highly Active Bidirectional Electron Transfer by a Self‐Assembled Electroactive Reduced‐Graphene‐Oxide‐Hybridized Biofilm

Low extracellular electron transfer performance is often a bottleneck in developing high‐performance bioelectrochemical systems. Herein, we show that the self‐assembly of graphene oxide and Shewanella oneidensis MR‐1 formed an electroactive, reduced‐graphene‐oxide‐hybridized, three‐dimensional macroporous biofilm, which enabled highly efficient bidirectional electron transfers between Shewanella and electrodes owing to high biomass incorporation and enhanced direct contact‐based extracellular electron transfer. This 3D electroactive biofilm delivered a 25‐fold increase in the outward current (oxidation current, electron flux from bacteria to electrodes) and 74‐fold increase in the inward current (reduction current, electron flux from electrodes to bacteria) over that of the naturally occurring biofilms.     

Functionalized Graphene as a Gatekeeper for Chiral Molecules: An Alternative Concept for Chiral Separation

We propose a new method of chiral separation using functionalized nanoporous graphene as an example. Computational simulations based on density functional theory show that the attachment of a suitable chiral “bouncer” molecule to the pore rim prevents the passage of the undesired enantiomer while letting its mirror image through.