等离子体法制氢的研究进展

本文讨论了利用等离子体从各种含氢原料中制氢所表现出的特异性能.当使用天然气为原料大规模制氢时,等离子体法的高能量密度可以极大地减少催化剂的使用和缩小生产空间;当用其他碳氢化合物为原料制氢时,等离子体法可以提高系统的灵活性、多变性,尤其在车载制氢上.等离子体发生源的多样性和等离子体转换器宽裕的设计空间可为降低能耗提供坚实的发展基础.     

Scaling Platinum-Catalyzed Hydrogen Dissociation on Corrugated Surfaces

We determine absolute reactivities for dissociation at low coordinated Pt sites. Two curved Pt(111) single-crystal surfaces allow us to probe either straight or highly kinked step edges with molecules impinging at a low impact energy. A model extracts the average reactivity of inner and outer kink atoms, which is compared to the reactivity of straight A- and B-type steps. Local surface coordination numbers do not adequately capture reactivity trends for H₂ dissociation. We utilize the increase of reactivity with step density to determine the area over which a step causes increased dissociation. This step-type specific reactive area extends beyond the step edge onto the (111) terrace. It defines the reaction cross-section for H₂ dissociation at the step, bypassing assumptions about contributions of individual types of surface atoms. Our results stress the non-local nature of H₂ interaction with a surface and provide insight into reactivity differences for nearly identical step sites.     

Functionalisation of Graphene Sensor Surfaces for the Specific Detection of Biomarkers

We report on a controllable and specific functionalisation route for graphene field-effect transistors (GFETs) for the recognition of small physiologically active molecules. Key element is the noncovalent functionalisation of the graphene surface with perylene bisimide (PBI) molecules directly on the growth substrate. This Functional Layer Transfer enables the homogeneous self-assembly of PBI molecules on graphene, onto which antibodies are subsequently immobilised. The sensor surface was characterised by atomic force microscopy, Raman spectroscopy and electrical measurements, showing superior performance over conventional functionalisation after transfer. Specific sensing of small molecules was realised by monitoring the electrical property changes of functionalised GFET devices upon the application of methamphetamine and cortisol. The concentration dependent electrical response of our sensors was determined down to a concentration of 300 ng ml⁻¹ for methamphetamine.     

Energy Application of Graphene Based Membrane: Hydrogen Separation

Hydrogen gas (H₂) is a viable energy carrier that has the potential to replace the traditional fossil fuels and contribute to achieving zero net emissions, making it an attractive option for a hydrogen-based society. However, current H₂ purification technologies are often limited by high energy consumption, and as a result, there is a growing demand for alternative techniques that offer higher H₂ purity and energy efficiency. Membrane separation has emerged as a promising approach for obtaining high-purity H₂ gas with low energy consumption. Nevertheless, despite years of development, commercial polymeric membranes have limited performance, prompting researchers to explore alternative materials. In this context, carbon-based membranes, specifically graphene-based nanomaterials, have gained significant attention as potential membrane materials due to their unique properties. In this review, we provide a comprehensive overview of carbon-based membranes for H₂ gas separation, fabrication of the membrane, and its characterization, including their advantages and limitations. We also explore the current technological challenges and suggest insights into future research directions, highlighting potential ways to improve graphene-based membranes performance for H₂ separations.     

Growth and Characterization of Graphene Layers on Different Kinds of Copper Surfaces

Graphene films were grown by chemical vapor deposition on Cu foil. The obtained samples were characterized by Raman spectroscopy, ellipsometry, X-ray photoelectron spectroscopy and electron back-scatter diffraction. We discuss the time-dependent changes in the samples, estimate the thickness of emerging Cu₂O beneath the graphene and check the orientation-dependent affinity to oxidation of distinct Cu grains, which also governs the manner in which the initial strong Cu-graphene coupling and strain in the graphene lattice is released. Effects of electropolishing on the quality and the Raman response of the grown graphene layers are studied by microtexture polarization analysis. The obtained data are compared with the Raman signal of graphene after transfer on glass substrate revealing the complex interaction of graphene with the Cu substrate.     

氢溴酸可控还原氧化石墨烯及氢气气敏性能

采用改进的Hummers法对石墨进行氧化处理制备大片径氧化石墨,经超声分散获得一定浓度的氧化石墨烯样品,并将其与氢溴酸水浴加热反应进行化学还原处理,改变氢溴酸的添加量,从而获得不同还原程度的氧化石墨烯样品。用AFM、 XRD、FT-IR、XPS及气敏测试仪对样品薄膜厚度、结构、官能团等变化规律及氢气气敏特性进行测试表征与分析。      

Reducing Properties of Superalkalis on Pyridinic Graphene Surfaces: a Computational Study

The hyperlithiated species (k=1, 2, 3, and 4) have been studied by quantum mechanical (QM) methods. Different structures have been localized for each molecule by the CBS-QB3 composite method: all the isomers show superalkali properties and strong tendency to donate an electron to carbon dioxide forming stable complexes. With the aim to find molecular systems able to stabilize superalkalis, geometries of complexes between superalkalis and pyridine and superalkalis and graphene surfaces doped with a pyridinic vacancy were calculated. The pyridinic graphene sheets were modeled with two finite molecular systems C₆₉H₂₁N₃ and C₁₁₇H₂₇N₃. The interaction with one pyridine molecule is quite weak and the superalkali maintains its structure and electron properties. The affinity for graphene sheets is instead stronger and the superalkalis tend to deform their geometry to better interact with the graphene surface. However, the superalkalis continue to show the tendency to transfer electrons to carbon dioxide reducing CO₂, as found in graphene absence.     

Structural Characteristics of Graphene Oxide Reduced by Hydrazine and Hydrogen

Theoretical and Experimental Chemistry - The composition of functional groups, morphology, defect structure, and surface fractal dimension DS of reduced graphene oxide (RGO) synthesized by...     

Laser-Induced Generation of Hydrogen in Water by Using Graphene Target

A new method of hydrogen generation from water, by irradiation with CW infrared laser diode of graphene scaffold immersed in solution, is reported. Hydrogen production was extremely efficient upon admixing NaCl into water. The efficiency of hydrogen production increased exponentially with laser power. It was shown that hydrogen production was highly efficient when the intense white light emission induced by laser irradiation of graphene foam was occurring. The mechanism of laser-induced dissociation of water is discussed. It was found that hydrogen production was extremely high, at about 80%, and assisted by a small emission of O₂, CO and CO₂ gases.     

Comparison of Chemical Composition and Hydrophilic Properties of Surfaces of Organic Polymers Treated in Various Low-Temperature Plasmas

High Energy Chemistry - A comparative study of the chemical composition and properties of poly(methyl methacrylate) and poly(ethylene terephthalate) after their treatment in various types of...     

Wrinkled Graphene Monoliths as Superabsorbing Building Blocks for Superhydrophobic and Superhydrophilic Surfaces

Superhydrophobic and superhydrophilic surfaces are of great interest because of a large range of applications, for example, as antifogging and self‐cleaning coatings, as antibiofouling paints for boats, in metal refining, and for water–oil separation. An aqueous ink based on three‐dimensional graphene monoliths (Gr) can be used for constructing both superhydrophobic and superhydrophilic surfaces on arbitrary substrates with different surficial structures from the meso‐ to the macroscale. The surface wettability of a Gr‐coated surface mainly depends on which additional layers (air for a superhydrophobic surface and water for a superhydrophilic surface) are adsorbed on the surface of the graphene sheets. Switching a Gr‐coated surface between being superhydrophobic and superhydrophilic can thus be easily achieved by drying and prewetting with ethanol. The Gr‐based superhydrophobic membranes or films should have great potential as efficient separators for fast and gravity‐driven oil–water separation.     

钇对石墨烯储氢性能的影响

应用基于密度泛函理论的第一性原理方法研究过渡金属钇（Y）修饰对石墨烯储氢性能的影响。考虑Y原子在石墨烯上易形成团簇,采用B原子掺杂有效阻止了团簇形成。通过模拟计算得到的改性体系稳定、储氢性能优异,可吸附6个H₂分子,平均吸附能范围为-0.539到-0.655 eV （per H₂）,理论上满足理想的氢吸附能范围。经Bader电荷初步计算和基于Y/B/graphene （G）体系吸附H₂分子的电子态密度及电荷差分密度图分析得,Y原子与石墨烯间通过电荷转移产生结合,与H₂分子则发生典型的Kubas型相互作用。Y原子改变了H₂分子与石墨烯基的电荷分布,成为连接两者电子云的桥梁,从而增强了H₂分子的吸附能。改性石墨烯体系吸附的均为氢分子,有利于在环境温度和压力条件下进行循环控制,是具有良好发展前景的储氢材料之一。     

Controlled Carbon Nitride Growth on Surfaces for Hydrogen Evolution Electrodes

Efficient and low‐cost electrocatalysts for the hydrogen evolution reaction are highly desired for future renewable energy systems. Described herein is the reduction of water to hydrogen using a metal‐free carbon nitride electrocatalyst which operates in neutral and alkaline environments. An efficient, easy, and general method for growing ordered carbon nitride on different electrodes was developed. The metal‐free catalyst demonstrates low overpotential values, which are comparable to those of non‐noble metals, with reasonable current densities. The facile deposition method enables the fabrication of many electronic and photoelectronic devices based on carbon nitride for renewable energy applications.     

氧化石墨烯基钴卟啉复合材料的电催化析氢反应

制备了5,10,15,20-四(苯基)卟啉钴配合物(CoTPP), 并利用该配合物与氧化石墨烯(GO)的π?π堆积作用组装了CoTPP/GO电催化产氢复合材料. 研究发现, 当CoTPP与GO的质量比为1∶15时, 复合材料的性能最佳. 该材料的拉曼和扫描电子显微镜结果显示, 与GO相比, CoTPP/GO复合材料表面的无序程度增加, 形貌改变有利于促进反应体系的电荷迁移与分离; 交流阻抗测试结果显示, 阻抗值由GO的1180 Ω降低为CoTPP/GO材料的734 Ω; 电化学测试结果显示, 析氢起始过电位由-761 mV降低为-337 mV, 塔菲尔斜率由296 mV/dec 降低至174 mV/dec, 法拉第效率却由23%提高至87%. 加入二苯硫醚(SPh₂)轴向配体后, CoTPP(SPh₂)/GO材料的析氢起始过电位进一步降低至-235 mV, 塔菲尔斜率降低至163 mV/dec, 法拉第效率提高至94%. 研究结果表明, 通过氧化石墨烯与金属卟啉的非共价键自组装是构筑石墨烯基电催化产氢材料的一个有效途径.     

Self-Assembly in Silane/Hydrogen Plasmas: from Silicon Atoms to Aromatic Silicon Nanocrystals

We theoretically predict that low pressure silane/hydrogen plasmas may present the ideal venue for the fabrication of a new nanostructured silicon material with strong aromatic properties. Precisely controlling the ratio of atomic and molecular hydrogen concentrations during the growth of hydrogenated silicon clusters in a pulsed plasma enhanced chemical vapor deposition reactor will allow us to “steer” the growth toward over-coordinated silicon nanocrystals that reveal aromatic properties as strong as those of benzene. In addition, those pure silicon nanocrystals demonstrate optical, electrical, and mechanical characteristics that could so far only be obtained by adding toxic or expensive elements (as PbS, PbSe, CdS, CdSe, or Au) in the cluster structure. Due to their light absorption not only in the ultraviolet, but also in the visible and the infrared spectrum, they might, for instance, play a major role for photovoltaic devices or in the hyperthermal treatment of cancer.     

氢原子在钯低指数表面上的吸附和扩散

采用氢－钯相互作用的五参数Ｍｏｒｓｅ势，用对势方法研究了氢原子在Ｐｄ（１００）、Ｐｄ（１１１）和Ｐｄ（１１０）低指数平坦表面上的吸附和扩散，得到氢原子在三个表面上的吸附位、吸附几何、结合能和本征振动等数据，计算结果和实验结果符合得很好。在此基础上，系统地研究了三个系统的吸附扩散势能面结构。     

铁氰化钴修饰石墨烯平面电极对过氧化氢的传感作用

利用高分子支撑法将气相沉积(CVD)石墨烯从铜基底上转移到聚对苯二甲酸乙二醇酯(PET)基底上,制备出石墨烯平面电极(GPE), 通过循环伏安法将铁氰化钴(CoHCF)纳米颗沉积到GPE上,得到铁氰化钴修饰石墨烯平面电极(CoHCF/GPE).研究表明,此电极对过氧化氢具有良好的传感作用,从而构建一种新型无酶过氧化氢传感器.此传感器在过氧化氢浓度为5.0-1200 μmol/L范围内,响应电流与浓度呈现良好的线性关系,检出限为7.1 nmol/L (S/N=3),响应时间约为2 s,具有稳定性好、抗干扰能力强、制备简单等优点.     

Radical Chain Polymerization Catalyzed by Graphene Oxide and Cooperative Hydrogen Bonding

Graphene oxide (GO) is effective in catalyzing a wide variety of organic reactions and a few types of polymerization reactions. No radical chain polymerizations catalyzed by GO have been reported. In this article, we probe the catalytic role and acceleration effect of GO for self‐initiated radical chain polymerizations of acrylic acid (AA) in the presence of GO and a pre‐existing polymer, poly(N‐vinylpyrrolidone) (PVP), from a calorimetric perspective. Gelation experiments and DSC studies show that GO can function as a catalyst to accelerate the radical chain polymerization of AA. Isothermal polymerization kinetic data shows that the addition of GO diminishes the induction periods and increases the polymerization rates, as indicated by the much enhanced overall kinetic rate constants and lowered activation energies. The catalytic effect of GO for the polymerization of AA is attributed to the acidity of GO and the hydrogen bonding interactions between GO and monomer molecules and/or polymers.

     

Composite Materials with 2D Graphene Structures: Applications for Hydrogen Energetics and Catalysis with Hydrogen Participation

The work presents the results of studies concerning preparation of graphene-like nanomaterials by graphite oxide reduction, preparation of nickel-graphene catalysts, magnesium-graphene, and carbon-graphene composites. Optimum conditions for preparing these materials and their functional characteristics are determined.