Nanoscale molybdenum disulfide (MoS2) has attracted ever-growing interest as one of the most prom... more Nanoscale molybdenum disulfide (MoS2) has attracted ever-growing interest as one of the most promising nonprecious catalysts for hydrogen evolution reaction (HER). However, the active sites of pristine MoS2 are located at the edges, leaving a large area of basal planes useless. Here, we systematically evaluate the capabilities of 16 kinds of structural defects including point defects (PDs) and grain boundaries (GBs) to activate the basal plane of MoS2 monolayer. Our first-principle calculations show that six types of defects (i.e., Vs, VMoS3, MoS2 PDs; 4|8a, S bridge, and Mo–Mo bond GBs) can greatly improve the HER performance of the in-plane domains of MoS2. More importantly, Vs and MoS2 PDs and S bridge and 4|8a GBs exhibit outstanding activity in both Heyrovsky and Tafel reactions as well. Moreover, the different HER activities of defects are well-understood by an amendatory band-center model, which is applicable to a broad class of systems with localized defect states. Our study provides a comprehensi...
Cu nanoparticles with different sizes, morphology, and surface structures exhibit distinct activi... more Cu nanoparticles with different sizes, morphology, and surface structures exhibit distinct activity and selectivity toward CO2 reduction reaction, while the reactive sites and reaction mechanisms are very controversial in experiments. In this study, we demonstrate the dynamic structure change of Cu clusters on graphite‐like carbon supports plays an important role in the multicarbon production by combining static calculations and ab‐initio molecular dynamic simulations. The mobility of Cu clusters on graphite is attributed to the near‐degenerate energies of various adsorption configurations, as the interaction between Cu atoms and surface C atoms is weaker than that of CuCu bonds in the tight cluster form. Such structure change of Cu clusters leads to step‐like irregular surface structures and appropriate interparticle distances, increasing the selectivity of multicarbon products by reducing the energy barriers of CC coupling effectively. In contrast, the large ratio of edge and corner sites on Cu clusters is responsible for the increased catalytic activity and selectivity for CO and H2 compared with Cu(100) surface, instead of hydrocarbon products like methane and ethylene. The detailed study reveals that the dynamic structure change of the catalysts results in roughened surface morphologies during catalytic reactions and plays an essential role in the selectivity of CO2 electro‐reduction, which should be paid more attention for studies on the reaction mechanisms.image
Journal of Physical Chemistry Letters, Jan 16, 2018
High carrier mobility and moderate band gap are two key properties of electronic device applicati... more High carrier mobility and moderate band gap are two key properties of electronic device applications. Two ultrathin two-dimensional (2D) semiconductors, namely, Bi2Te2S and Bi2Te2Se nanosheets, with novel electronic and optical properties are predicted based on first-principles calculations. The Bi2Te2S and Bi2Te2Se monolayers own moderate band gaps (∼0.7 eV) and high electron mobilities (∼20 000 cm2 V-1 s-1), and they can absorb sunlight efficiently through the whole incident solar spectrum. Meanwhile, layer-dependent exponential decay band gaps are also unveiled. The relatively low interlayer binding energies suggest that these monolayers can be easily exfoliated from bulk structures. Their high dynamical and thermal stabilities are further verified by phonon dispersion calculations and ab initio molecular dynamics simulations. The exceptional properties render Bi2Te2X (X = S, Se) monolayers promising candidates in future high-speed (opto)electronic devices.
Synthesis of two-dimensional (2D) metal chalcogenide based half-metallic nanosheets is in high de... more Synthesis of two-dimensional (2D) metal chalcogenide based half-metallic nanosheets is in high demand for modern electronics and spintronics applications. Herein, we predict from first-principles calculations that the 2D heterostructure Co/MoS2, consisting of a monolayer of Co atoms deposited on a single MoS2 sheet, possesses robust ferromagnetic and half-metallic features and exhibits 100% spin-filter efficiency within a broad bias range. Its ferromagnetic and half-metallic nature persists even when overlaid with a graphene sheet. Because of the relatively strong surface binding energy and low clustering ratio of Co atoms on the MoS2 surface, we predict that the heterostructure is synthesizable via wetting deposition of Co on MoS2 by electron-beam evaporation technique. Our work strongly suggests Co/MoS2 as a compelling and feasible candidate for highly effective information and high-density memory devices.
Molybdenum disulfide (MoS2) is considered to be one of the most promising low-cost catalysts for ... more Molybdenum disulfide (MoS2) is considered to be one of the most promising low-cost catalysts for the hydrogen evolution reaction (HER). So far, the limited active sites and high kinetic barriers for H2 evolution still impede its practical application in electrochemical water splitting. In this work, on the basis of comprehensive first-principles calculations, we predict that the recently produced template-grown MoS2 nanowires (NWs) on Au(755) surfaces have both ultralow kinetic barriers for H2 evolution and ultrahigh active site density simultaneously. The calculated kinetic barrier of H2 evolution through the Tafel mechanism is only 0.49 eV on the Mo edges, making the Volmer–Tafel mechanism operative, and the Tafel slope can be as low as 30 mV/dec. Through substitution of the Au(755) substrate with non-noble metals, such as Ni(755) and Cu(755), the activity can be maintained. This work provides a possible way to achieve the ultrahigh HER activity of MoS2-based catalysts.
Nanoscale molybdenum disulfide (MoS2) has attracted ever-growing interest as one of the most prom... more Nanoscale molybdenum disulfide (MoS2) has attracted ever-growing interest as one of the most promising nonprecious catalysts for hydrogen evolution reaction (HER). However, the active sites of pristine MoS2 are located at the edges, leaving a large area of basal planes useless. Here, we systematically evaluate the capabilities of 16 kinds of structural defects including point defects (PDs) and grain boundaries (GBs) to activate the basal plane of MoS2 monolayer. Our first-principle calculations show that six types of defects (i.e., Vs, VMoS3, MoS2 PDs; 4|8a, S bridge, and Mo–Mo bond GBs) can greatly improve the HER performance of the in-plane domains of MoS2. More importantly, Vs and MoS2 PDs and S bridge and 4|8a GBs exhibit outstanding activity in both Heyrovsky and Tafel reactions as well. Moreover, the different HER activities of defects are well-understood by an amendatory band-center model, which is applicable to a broad class of systems with localized defect states. Our study provides a comprehensi...
Cu nanoparticles with different sizes, morphology, and surface structures exhibit distinct activi... more Cu nanoparticles with different sizes, morphology, and surface structures exhibit distinct activity and selectivity toward CO2 reduction reaction, while the reactive sites and reaction mechanisms are very controversial in experiments. In this study, we demonstrate the dynamic structure change of Cu clusters on graphite‐like carbon supports plays an important role in the multicarbon production by combining static calculations and ab‐initio molecular dynamic simulations. The mobility of Cu clusters on graphite is attributed to the near‐degenerate energies of various adsorption configurations, as the interaction between Cu atoms and surface C atoms is weaker than that of CuCu bonds in the tight cluster form. Such structure change of Cu clusters leads to step‐like irregular surface structures and appropriate interparticle distances, increasing the selectivity of multicarbon products by reducing the energy barriers of CC coupling effectively. In contrast, the large ratio of edge and corner sites on Cu clusters is responsible for the increased catalytic activity and selectivity for CO and H2 compared with Cu(100) surface, instead of hydrocarbon products like methane and ethylene. The detailed study reveals that the dynamic structure change of the catalysts results in roughened surface morphologies during catalytic reactions and plays an essential role in the selectivity of CO2 electro‐reduction, which should be paid more attention for studies on the reaction mechanisms.image
Journal of Physical Chemistry Letters, Jan 16, 2018
High carrier mobility and moderate band gap are two key properties of electronic device applicati... more High carrier mobility and moderate band gap are two key properties of electronic device applications. Two ultrathin two-dimensional (2D) semiconductors, namely, Bi2Te2S and Bi2Te2Se nanosheets, with novel electronic and optical properties are predicted based on first-principles calculations. The Bi2Te2S and Bi2Te2Se monolayers own moderate band gaps (∼0.7 eV) and high electron mobilities (∼20 000 cm2 V-1 s-1), and they can absorb sunlight efficiently through the whole incident solar spectrum. Meanwhile, layer-dependent exponential decay band gaps are also unveiled. The relatively low interlayer binding energies suggest that these monolayers can be easily exfoliated from bulk structures. Their high dynamical and thermal stabilities are further verified by phonon dispersion calculations and ab initio molecular dynamics simulations. The exceptional properties render Bi2Te2X (X = S, Se) monolayers promising candidates in future high-speed (opto)electronic devices.
Synthesis of two-dimensional (2D) metal chalcogenide based half-metallic nanosheets is in high de... more Synthesis of two-dimensional (2D) metal chalcogenide based half-metallic nanosheets is in high demand for modern electronics and spintronics applications. Herein, we predict from first-principles calculations that the 2D heterostructure Co/MoS2, consisting of a monolayer of Co atoms deposited on a single MoS2 sheet, possesses robust ferromagnetic and half-metallic features and exhibits 100% spin-filter efficiency within a broad bias range. Its ferromagnetic and half-metallic nature persists even when overlaid with a graphene sheet. Because of the relatively strong surface binding energy and low clustering ratio of Co atoms on the MoS2 surface, we predict that the heterostructure is synthesizable via wetting deposition of Co on MoS2 by electron-beam evaporation technique. Our work strongly suggests Co/MoS2 as a compelling and feasible candidate for highly effective information and high-density memory devices.
Molybdenum disulfide (MoS2) is considered to be one of the most promising low-cost catalysts for ... more Molybdenum disulfide (MoS2) is considered to be one of the most promising low-cost catalysts for the hydrogen evolution reaction (HER). So far, the limited active sites and high kinetic barriers for H2 evolution still impede its practical application in electrochemical water splitting. In this work, on the basis of comprehensive first-principles calculations, we predict that the recently produced template-grown MoS2 nanowires (NWs) on Au(755) surfaces have both ultralow kinetic barriers for H2 evolution and ultrahigh active site density simultaneously. The calculated kinetic barrier of H2 evolution through the Tafel mechanism is only 0.49 eV on the Mo edges, making the Volmer–Tafel mechanism operative, and the Tafel slope can be as low as 30 mV/dec. Through substitution of the Au(755) substrate with non-noble metals, such as Ni(755) and Cu(755), the activity can be maintained. This work provides a possible way to achieve the ultrahigh HER activity of MoS2-based catalysts.
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Papers by Yixin Ouyang