Morphology engineering and etching of graphene domain by low-pressure chemical vapor deposition

Controlled growth of single-crystal high-quality ‘track-and-field ground’ shaped graphene domains and the morphological evolution from hexagonal to hexagram graphene domain even square and circular graphene domain has been achieved by low-pressure CVD on solid copper substrate, thereby demonstrating that the shape of the graphene grains can potentially be precisely tuned by optimizing growth parameters. The etching reaction of graphene has also been studied, and results show that a low flow rate of hydrogen (99.999%) is favorable to form hexagonal structure for the etching reaction of graphene due to the exist of oxygen or oxidizing impurities in hydrogen gas commonly used. Controlled growth and etching reaction of graphene determine the final shape of graphene domains and all these efforts contribute to the study of size and morphology and the growth mechanism of graphene domains.     

具备高效析氢催化效率的三维多孔氮化钒八面体催化剂

随着中国经济和社会的快速发展,能源需求和环境污染问题也日益渐长. 发展和开发高效清洁的新能源燃料可以有效地缓解能源危机和环境污染. 如今,研发高效、环境友好和低成本的催化剂仍是析氢反应的研究重点. 在此项研究中,作者首先通过煅烧处理方式制备了一种三维多孔的氮化钒八面体结构型的催化剂. 该催化剂具备高效的析氢效率,包括较低的过电位94.0 mV（在-10 mA·cm^-2时）,塔菲尔斜率为54.6 mV·dec^-1,以及在酸性条件80小时展现出的优良稳定性,该氮化钒的析氢催化效率优于许多报道过的氮化物,其优良的催化效率可以归因于它独一无二的自身性质和大量的活性位点.     

TargetATPsite: A template‐free method for ATP‐binding sites prediction with residue evolution image sparse representation and classifier ensemble

Understanding the interactions between proteins and ligands is critical for protein function annotations and drug discovery. We report a new sequence‐based template‐free predictor (TargetATPsite) to identify the Adenosine‐5′‐triphosphate (ATP) binding sites with machine‐learning approaches. Two steps are implemented in TargetATPsite: binding residues and pockets predictions, respectively. To predict the binding residues, a novel image sparse representation technique is proposed to encode residue evolution information treated as the input features. An ensemble classifier constructed based on support vector machines (SVM) from multiple random under‐samplings is used as the prediction model, which is effective for dealing with imbalance phenomenon between the positive and negative training samples. Compared with the existing ATP‐specific sequence‐based predictors, TargetATPsite is featured by the second step of possessing the capability of further identifying the binding pockets from the predicted binding residues through a spatial clustering algorithm. Experimental results on three benchmark datasets demonstrate the efficacy of TargetATPsite. © 2013 Wiley Periodicals, Inc.     

Porous Molybdenum Carbide Nanostructures Synthesized on Carbon Cloth by CVD for Efficient Hydrogen Production

Molybdenum carbide (Mo₂C) is a promising noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER), due to its structural and electronic merits, such as high conductivity, metallic band states and wide pH applicability. Here, a simple CVD process was developed for synthesis of a Mo₂C on carbon cloth (Mo₂C@CC) electrode with carbon cloth as carbon source and MoO₃ as the Mo precursor. XRD, Raman, XPS and SEM results of Mo₂C@CC with different amounts of MoO₃ and growth temperatures suggested a two-step synthetic mechanism, and porous Mo₂C nanostructures were obtained on carbon cloth with 50 mg MoO₃ at 850 °C (Mo₂C-850(50)). With the merits of unique porous nanostructures, a low overpotential of 72 mV at current density of 10 mA cm⁻² and a small Tafel slope of 52.8 mV dec⁻¹ was achieved for Mo₂C-850(50) in 1.0 m KOH. The dual role of carbon cloth as electrode and carbon source resulted into intimate adhesion of Mo₂C on carbon cloth, offering fast electron transfer at the interface. Cyclic voltammetry measurements for 5000 cycles revealed that Mo₂C@CC had excellent electrochemical stability. This work provides a novel strategy for synthesizing Mo₂C and other efficient carbide electrocatalysts for HER and other applications, such as supercapacitors and lithium-ion batteries.     

Structural Evolution and Electronic Properties of Au2Gen-/0 (n=1-8) Clusters: Anion Photoelectron Spectroscopy and Theoretical Calculations

Investigating the structures and properties of Au-Ge mixed clusters can give insight into the microscopic mechanisms in gold-catalyzed Ge films and can also provide valuable information for the production of germanium-based functional materials. In this work, size-selected anion photoelectron spectroscopy and theoretical calculations were used to explore the structural evolution and electronic properties of Au₂Ge_n^-/0 (n=1-8) clusters. It is found that the two Au atoms in Au₂Ge_n^-/0 (n=1-8) showed high coordination numbers and weak aurophilic interactions. The global minima of Au₂Ge_n^- anions and Au₂Ge_n neutrals are in spin doublet and singlet states, respectively. Au₂Ge_n^- anions and Au₂Ge_n neutrals showed similar structural features, except for Au₂Ge₄^-/0 and Au₂Ge₅^-/0. The C_2v symmetric V-shaped structure is observed for Au₂Ge₁^-/0, while Au₂Ge₂^-/0 has a C_2v symmetric dibridged structure. Au₂Ge₃^-/0 can be viewed as the two Au atoms attached to different Ge-Ge bonds of Ge₃ triangle. Au₂Ge₄^- has two Au atoms edge-capping Ge₄ tetrahedron, while Au₂Ge₄ neutral adopts a C_2v symmetric double Au atoms face-capping Ge₄ rhombus. Au₂Ge_5-8^-/0 show triangular, tetragonal, and pentagonal prism-based geometries. Au₂Ge₆ adopts a C_2v symmetric tetragonal prism structure and exhibits σ plus π double bonding characters.     

基于磺酰基杯[4]芳烃的Co16笼簇的合成、结构及电化学性质

以氯化钴、 对叔丁基磺酰杯[4]芳烃(H₄TC4A-SO₂)和非对称性3-(1H-四唑-5-基)苯甲酸(H₂L)为原料, 通过溶剂热法合成了一个具有四面体配位笼结构的16核化合物[Co₁₆(TC4A-SO₂)₄(OH)₄(L)₈]·[(C₈H₂₀N)(C₄H₁₂N)₂(C₂H₈N)]·solvent(Co₁₆-TC4A-SO₂). 采用X射线单晶衍射、 X射线粉末衍射、 热重分析、 红外光谱方法对配合物进行了表征. 将Co₁₆-TC4A-SO₂笼簇直接负载到碳纸上(Co₁₆-TC4A-SO₂/CP)用作工作电极, 其对析氧反应(OER)展现出较好的催化性能. 在1 mol/L KOH中, Co₁₆-TC4A-SO₂/CP在343.8 mV的过电位下达到10.0 mA/cm ²电流密度, Tafel斜率为79.31 mV/dec, 并且在20.0 mA/cm ²电流密度下表现出长达48 h的催化稳定性.     

一步法合成的FeOOH/黑磷纳米复合材料协同实现体系优异的析氧性能

通过水热法,在黑磷(BP)纳米片表面生长FeOOH纳米材料,制备出FeOOH/BP纳米复合材料。作为电化学析氧反应(OER)催化剂,该复合材料在20 mA·cm^-2时的过电位仅为191 mV,Tafel斜率为49.9 mV dec^-1;在循环1 000圈后,过电位仅仅增加了3 mV,且循环过程中元素价态不变,表现出优秀的稳定性。纳米FeOOH负载于BP表面,客观上能隔断氧气对BP的氧化,保护BP的载流子传导性能。同时,生长的FeOOH颗粒尺度小,结晶性弱,这有利于丰富其活性位点,增大活性面积。     

CoFeOx/MoO2准平行纳米阵列电极的析氢性能

利用CoFe层状双金属氢氧化物(CoFe LDH)准平行纳米片阵列作为载体前驱体,通过原位负载及煅烧方式,实现了含有氧空位的 MoO₂纳米颗粒在纳米片阵列表面的生长。电化学研究结果表明,所得 CoFeO_x/MoO₂纳米阵列电极具有高析氢反应(HER)催化活性。该电极在10和1 000 mA·cm^-2时的HER过电位分别为40和217 mV。在50 mA·cm^-2的电流密度下,该电极可以稳定运行125 h。     

析氢反应动力学的交流阻抗法研究

利用交流阻抗法测定析氢电化学动力学参数，得到与极化曲线法一致的结果，为确定复杂析氢过程速率的决定步骤提供了判据。