英语原文共 10 页
Two-Dimensional Hybrid Nanosheets of Tungsten Disulfide and Reduced Graphene Oxide as Catalysts for Enhanced Hydrogen Evolution
Two-dimensional (2D) transition-metal dichalcogenide (TMD) nanosheets have emerged as a fascinating new class of materials for catalysis. These nanosheets are active for several important catalysis reactions including hydrogen evolution from water. The rich chemistry of TMDs combined with numerous strategies that allow tuning of their electronic properties make these materials very attractive for understanding the fundamental principles of electro- and photocatalysis, as well as for developing highly efﬁcient, renewable, and affordable catalysts for large-scale production of hydrogen. 
Early studies have shown that TMDs and in particular MoS2 are useful catalysts in hydro-desulfurization (HDS) reactions. Initial studies of the HDS reaction using scanning tunneling microscopy (STM) and thiophene as the reactant have revealed that adsorption occurs at the edges of the TMDs. TMDs possess edges that comprise chalcogen or transition-metal atoms. Edges can also be covered with 0%, 50%, 75%, or 100% of chalcogen atoms, depending on the synthesis conditions and the size of the nanosheets. STM images of MoS2 nanoclusters reveal bright brims, indicating that the 1D edges are metallic, as conﬁrmed by DFT calculations. Understanding the edge structure and conductivity has been important in elucidating the fundamental HDS reaction mechanisms. 
早期的研究表明TMDs，特别是MoS2, 是加氢脱硫( HDS )反应中非常有用的催化剂。使用扫描隧道电子显微镜（STM）对噻吩作为反应物的HDS反应的初步研究显示，这种吸附发生在TMD的边缘。TMDs具有由硫属原子或者过渡金属原子构成的边缘。根据合成的条件和纳米片的尺寸，它的边缘可以被硫属原子不同比例覆盖，如0%，50%，75%或者100%。MoS2纳米团簇的扫描电子显微镜显示呈现明亮的边缘，表明一维边是金属性的，这个结论后面也被DFT计算所证实。理解边缘结构和导电性对于阐明加氢脱硫反应机理是很重要的。
In the past 10 years, two dimensional (2D) materials have become the focus of researchers working on nanomaterials because of their interesting optical and electronic properties that arise from the absence of the third dimension. The interesting surface and electronic properties of 2D materials have been widely studied and applied to a variety of proof-of-concept devices. One avenue of research that seems particularly promising with 2D transition-metal dichalcogenides (TMDs) is electrocatalysis for the hydrogen evolution reaction (HER). A key advantage of 2D TMDs is that all of the catalytically active sites are exposed due to the atomically thin nature of the nanosheets.
Layered TMDs consist of alternating sheets of transition-metal atoms sandwiched between two chalcogen atoms. The oxidation degree of the metal and the chalcogen atoms is 4 and minus;2, respectively. The difference in oxidation degree induces the formation of strong ionic bonds between the metal and the chalcogen atoms, which preserve the structure of the nanosheets, whereas the existence of weak van der Waals bonds between the individual layers enables the exfoliation of bulk crystals down to single layers. A variety of compounds with different transition metals and chalcogens can be realized. The variations in chemistry of the compounds leads to dramatic differences in their catalytic activity, providing a rich platform for studying the fundamental properties, as well as laying the ground work for future technologies.In addition to the compositional tunability, the crystal structure and strain can also be varied to enhance the catalytic performance of 2D-TMD-based catalysts for the HER.
Such strategies have already been applied in electronic and optical devices for improving the performance and studying fundamental behavior of the materials, but fewer examples have been reported for electrocatalysis.
The need for renewable energy has driven efforts for the development of affordable, earth-abundant catalysts for the production of hydrogen. TMDs have demonstrated promising properties as electro- and photocatalysts for the HER. Metallic TMDs have natural advantages since they can be active from their basal plane with a free energy for hydrogen adsorption that is close to thermo-neutral, and they offer good electrical conductivity. Besides the enhancement of electrocatalytic properties, TMDs also hold promise as photocatalysts. The rich properties of 2D TMDs can be used to harvest sunlight efﬁciently, separate electron–hole pairs and drive electrons to active sites to facilitate catalytic reactions.It is known that the electronic structure strongly inﬂuences the catalytic properties of materials.TMDs offer opportunities for varying and therefore testing different atomic and electronic structures. For example, MoS2or WS2 nanosheets can be prepared with semiconducting trigonal prismatic (2H phase) or metallic octahedral (1T phase) structures by increasing the electron density in the d orbitals of the metal atoms (Figure 3a). Electrochemical stability is a major concern for electro- or photo catalysts. Experimentally, it has been observed that the transition temperature is relatively high compared to the typical temperatures for the HER: 100 °C and 200 °C for 1T-MoS2
- 关于2D二硫化钼( MoS2)助催化剂在光催化产氢领域的综述外文翻译资料