In article number https://doi.org/10.1002/adfm.2019063851906385, Jinhua Hong, Feng Ding, Hua Xu, and co‐workers reveal a nanoassembly growth model of low symmetry 2D materials to understand the formation mechanism of grain boundaries and subdomains in CVD grown 1T’ ReS2.
Published in: "Advanced Functional Materials".
In article number https://doi.org/10.1002/adfm.2019063851906385, Jinhua Hong, Feng Ding, Hua Xu, and co‐workers reveal a nanoassembly growth model of low symmetry 2D materials to understand the formation mechanism of grain boundaries and subdomains in CVD grown 1T’ ReS2.
Published in: "Advanced Functional Materials".
Colloidal synthesis of rhenium disulfide nanosheets enables a simple and cost‐effective exploitation of its peculiar layer‐independent properties for gas‐sensing and electrochemical H2 production. The surface functionalization of the nanosheets leads to sensitive and fast response gas sensors, while their assembly with carbon nanotubes enhances its electrocatalytic activity, making both device performances competitive with chemical vapor deposition rhenium disulfide. Abstract Among the large family of transition metal dichalcogenides, recently ReS2 has stood out due to its nearly layer‐independent optoelectronic and physicochemical properties related to its 1T distorted octahedral structure. This structure leads to strong in‐plane anisotropy, and the presence of active sites at its surface makes ReS2 interesting for gas sensing and catalysts applications. However, current fabrication methods use chemical or physical vapor deposition (CVD or PVD) processes that are costly, time‐consuming and complex, therefore limiting its large‐scale production and exploitation. To address this issue, a colloidal synthesis approach is developed, which allows the production of ReS2 at temperatures below 360 °C and with reaction times shorter than 2h. By combining the solution‐based synthesis with surface functionalization strategies, the feasibility of colloidal ReS2 nanosheet films for sensing different gases is demonstrated with highly competitive performance in comparison with devices built with CVD‐grown ReS2 and MoS2. In addition, the integration of the ReS2 nanosheet films in assemblies together with carbon nanotubes allows to fabricate electrodes for electrocatalysis for H2 production in both acid and alkaline conditions. Results from proof‐of‐principle devices show an electrocatalytic overpotential competitive with devices based on ReS2 produced by
Published in: "Small".
Colloidal synthesis of rhenium disulfide nanosheets enables a simple and cost‐effective exploitation of its peculiar layer‐independent properties for gas‐sensing and electrochemical H2 production. The surface functionalization of the nanosheets leads to sensitive and fast response gas sensors, while their assembly with carbon nanotubes enhances its electrocatalytic activity, making both device performances competitive with chemical vapor deposition rhenium disulfide. Abstract Among the large family of transition metal dichalcogenides, recently ReS2 has stood out due to its nearly layer‐independent optoelectronic and physicochemical properties related to its 1T distorted octahedral structure. This structure leads to strong in‐plane anisotropy, and the presence of active sites at its surface makes ReS2 interesting for gas sensing and catalysts applications. However, current fabrication methods use chemical or physical vapor deposition (CVD or PVD) processes that are costly, time‐consuming and complex, therefore limiting its large‐scale production and exploitation. To address this issue, a colloidal synthesis approach is developed, which allows the production of ReS2 at temperatures below 360 °C and with reaction times shorter than 2h. By combining the solution‐based synthesis with surface functionalization strategies, the feasibility of colloidal ReS2 nanosheet films for sensing different gases is demonstrated with highly competitive performance in comparison with devices built with CVD‐grown ReS2 and MoS2. In addition, the integration of the ReS2 nanosheet films in assemblies together with carbon nanotubes allows to fabricate electrodes for electrocatalysis for H2 production in both acid and alkaline conditions. Results from proof‐of‐principle devices show an electrocatalytic overpotential competitive with devices based on ReS2 produced by
Published in: "Small".
Circular polarized photocurrent is observed near the electrodes on a few-layer ReS2sample at room temperature. For both electrodes, the spatial distribution of the circular polarized photocurrent shows a feature of two wings, with one positive and the other negative. We suggest that this phenomenon arises from the inverse spin Hall effect due to local electric field near the electrode. Bias voltage that modulates this field further controls the sign and magnitude of the inverse spin Hall effect photocurrent. Our research shows that electric field near electrodes has a significant impact on spin transmission operation, hence it could be taken into account for manufacturing spintronic devices in future.
Published in: "arXiv Material Science".
A scalable stacking‐hinderable strategy is developed to enable exclusive single‐layer growth mode for transition metal dichalcogenides selectively sandwiched by surfactant molecules. These can act as efficient solar‐driven photocatalysts for solar H2 fuel production from hydrogen‐stored liquid carrier—methanol. Abstract Molecular surfactants are widely used to control low‐dimensional morphologies, including 2D nanomaterials in colloidal chemical synthesis, but it is still highly challenging to accurately control single‐layer growth for 2D materials. A scalable stacking‐hinderable strategy to not only enable exclusive single‐layer growth mode for transition metal dichalcogenides (TMDs) selectively sandwiched by surfactant molecules but also retain sandwiched single‐layer TMDs’ photoredox activities is developed. The single‐layer growth mechanism is well explained by theoretical calculation. Three types of single‐layer TMDs, including MoS2, WS2, and ReS2, are successfully synthesized and demonstrated in solar H2 fuel production from hydrogen‐stored liquid carrier—methanol. Such H2 fuel production from single‐layer MoS2 nanosheets is CO x‐free and reliably workable under room temperature and normal pressure with the generation rate reaching ≈617 µmole g−1 h−1 and excellent photoredox endurability. This strategy opens up the feasible avenue to develop methanol‐storable solar H2 fuel with facile chemical rebonding actualized by 2D single‐layer photocatalysts.
Published in: "Advanced Materials".
Single layer (SL) two-dimensional transition metal dichalcogenides (TMDs), such as MoS2, ReS2, WSe2, and MoTe2 have now become the focus of intensive fundamental and applied researches due to their intriguing and tunable physical properties. These materials exhibit a broad range of structural phases that can be induced via elastic strain, chemical doping, and electrostatic field effect. These transitions in turn can open and close the band gap of SL-TMDs, leading to metal-insulator transitions, and lead to emergence of more complex quantum phenomena. These considerations necessitate detailed understanding of the mesoscopic mechanisms of these structural phase transitions. Here we develop the Landau-type thermodynamic description of SL-TMDs on example of SL-(MoS2)1-x-(ReS2)x system and analyze the free energy surfaces, phase diagrams, and order parameter behavior. Our results predict the existence of multiple structural phases with 2-, 6- and 12-fold degenerated energy minima for in-plane and out of plane order parameters. This analysis suggests that out-of-plane ferroelectricity can exist in many of these phases, with the switchable polarization being proportional to the out-of-plane order parameter. We further predict that the domain walls in SL-(MoS2)1-x-(ReS2)x should become conductive above a certain strain threshold.
Published in: "arXiv Material Science".
A scalable stacking‐hinderable strategy is developed to enable exclusive single‐layer growth mode for transition metal dichalcogenides selectively sandwiched by surfactant molecules. These can act as efficient solar‐driven photocatalysts for solar H2 fuel production from hydrogen‐stored liquid carrier—methanol. Abstract Molecular surfactants are widely used to control low‐dimensional morphologies, including 2D nanomaterials in colloidal chemical synthesis, but it is still highly challenging to accurately control single‐layer growth for 2D materials. A scalable stacking‐hinderable strategy to not only enable exclusive single‐layer growth mode for transition metal dichalcogenides (TMDs) selectively sandwiched by surfactant molecules but also retain sandwiched single‐layer TMDs’ photoredox activities is developed. The single‐layer growth mechanism is well explained by theoretical calculation. Three types of single‐layer TMDs, including MoS2, WS2, and ReS2, are successfully synthesized and demonstrated in solar H2 fuel production from hydrogen‐stored liquid carrier—methanol. Such H2 fuel production from single‐layer MoS2 nanosheets is CO x‐free and reliably workable under room temperature and normal pressure with the generation rate reaching ≈617 µmole g−1 h−1 and excellent photoredox endurability. This strategy opens up the feasible avenue to develop methanol‐storable solar H2 fuel with facile chemical rebonding actualized by 2D single‐layer photocatalysts.
Published in: "Advanced Materials".
A scalable stacking‐hinderable strategy is developed to enable exclusive single‐layer growth mode for transition metal dichalcogenides selectively sandwiched by surfactant molecules. These can act as efficient solar‐driven photocatalysts for solar H2 fuel production from hydrogen‐stored liquid carrier—methanol. Abstract Molecular surfactants are widely used to control low‐dimensional morphologies, including 2D nanomaterials in colloidal chemical synthesis, but it is still highly challenging to accurately control single‐layer growth for 2D materials. A scalable stacking‐hinderable strategy to not only enable exclusive single‐layer growth mode for transition metal dichalcogenides (TMDs) selectively sandwiched by surfactant molecules but also retain sandwiched single‐layer TMDs’ photoredox activities is developed. The single‐layer growth mechanism is well explained by theoretical calculation. Three types of single‐layer TMDs, including MoS2, WS2, and ReS2, are successfully synthesized and demonstrated in solar H2 fuel production from hydrogen‐stored liquid carrier—methanol. Such H2 fuel production from single‐layer MoS2 nanosheets is CO x‐free and reliably workable under room temperature and normal pressure with the generation rate reaching ≈617 µmole g−1 h−1 and excellent photoredox endurability. This strategy opens up the feasible avenue to develop methanol‐storable solar H2 fuel with facile chemical rebonding actualized by 2D single‐layer photocatalysts.
Published in: "Advanced Materials".
Charged excitons (trions), with a large binding energy (≈60 meV) in anisotropic, atomically thin rhenium dichalcogenides (ReS2), are discovered by tuning carrier density. Strongly polarized anisotropic emission from these trions are also experimentally observed. Abstract Experimentally observed, stable trions with large binding energy (≈25 meV) in atomically thin monolayer 2D transition metal dichalcogenides MX2 (M = Mo, W, X = S, Se, and Te) with an isotropic crystal structure have been extensively studied. In contrast, the characteristics of trions in atomically thin 2D materials with an anisotropic crystal structure are not completely understood. Low‐temperature photoluminescence (PL) spectroscopy in few‐layer ReS2 with an anisotropic crystal structure by applying a gate voltage is described. A new PL peak that emerges below the lower‐energy side of neutral excitons obtained by tuning the gate voltages is attributed to emission from negative trions. Furthermore, the trion binding energy that is strongly dependent on the layer thickness reaches a large value of ≈60 meV in 1L–ReS2, which is ≈2 times larger than that in other isotropic 2D materials (MX2). The enhancement of the binding energy reflects the quasi‐1D nature of the trions in anisotropic atomically thin ReS2. These experimental observations will promote a better understanding of the optical response and applications in new categories of the anisotropic atomically thin 2D materials with a quasi‐1D nature.
Published in: "Advanced Functional Materials".
Charged excitons (trions), with a large binding energy (≈60 meV) in anisotropic, atomically thin rhenium dichalcogenides (ReS2), are discovered by tuning carrier density. Strongly polarized anisotropic emission from these trions are also experimentally observed. Abstract Experimentally observed, stable trions with large binding energy (≈25 meV) in atomically thin monolayer 2D transition metal dichalcogenides MX2 (M = Mo, W, X = S, Se, and Te) with an isotropic crystal structure have been extensively studied. In contrast, the characteristics of trions in atomically thin 2D materials with an anisotropic crystal structure are not completely understood. Low‐temperature photoluminescence (PL) spectroscopy in few‐layer ReS2 with an anisotropic crystal structure by applying a gate voltage is described. A new PL peak that emerges below the lower‐energy side of neutral excitons obtained by tuning the gate voltages is attributed to emission from negative trions. Furthermore, the trion binding energy that is strongly dependent on the layer thickness reaches a large value of ≈60 meV in 1L–ReS2, which is ≈2 times larger than that in other isotropic 2D materials (MX2). The enhancement of the binding energy reflects the quasi‐1D nature of the trions in anisotropic atomically thin ReS2. These experimental observations will promote a better understanding of the optical response and applications in new categories of the anisotropic atomically thin 2D materials with a quasi‐1D nature.
Published in: "Advanced Functional Materials".
Charged excitons (trions), with a large binding energy (≈60 meV) in anisotropic, atomically thin rhenium dichalcogenides (ReS2), are discovered by tuning carrier density. Strongly polarized anisotropic emission from these trions are also experimentally observed. Abstract Experimentally observed, stable trions with large binding energy (≈25 meV) in atomically thin monolayer 2D transition metal dichalcogenides MX2 (M = Mo, W, X = S, Se, and Te) with an isotropic crystal structure have been extensively studied. In contrast, the characteristics of trions in atomically thin 2D materials with an anisotropic crystal structure are not completely understood. Low‐temperature photoluminescence (PL) spectroscopy in few‐layer ReS2 with an anisotropic crystal structure by applying a gate voltage is described. A new PL peak that emerges below the lower‐energy side of neutral excitons obtained by tuning the gate voltages is attributed to emission from negative trions. Furthermore, the trion binding energy that is strongly dependent on the layer thickness reaches a large value of ≈60 meV in 1L–ReS2, which is ≈2 times larger than that in other isotropic 2D materials (MX2). The enhancement of the binding energy reflects the quasi‐1D nature of the trions in anisotropic atomically thin ReS2. These experimental observations will promote a better understanding of the optical response and applications in new categories of the anisotropic atomically thin 2D materials with a quasi‐1D nature.
Published in: "Advanced Functional Materials".
Nanoassembly growth model of low‐symmetry 2D materials is revealed to understand the formation mechanism of grain boundary and subdomain in CVD‐grown 1T′ ReS2. The controlled construct of diverse grain boundary structures combined with their novel properties will open up new prospects for the grain boundary‐mediated engineering of material properties and applications. Abstract Grain boundaries (GBs) significantly affect the electrical, optical, magnetic, and mechanical properties of 2D materials. An anisotropic 2D material like ReS2 provides unprecedented opportunities to explore novel GB properties, since the reduced lattice symmetry offers greater degrees of freedom to build new GB structures. Here the atomic structure and formation mechanism of unusual multidomain and diverse GB structures in the vapor phase synthesized ReS2 atomic layers are reported. Using high‐resolution electron microscopy, two major categories of GBs are observed in each ReS2 domain, namely, the joint GB including three structures, and the GBs formed from a reconstruction of Re4‐chains including seven different structures. Based on the experimental observations, a novel “nanoassembly growth model” is proposed to elucidate the growth process of ReS2, where three types of Re4‐chain reconstruction give rise to a multidomain structure. Moreover, it is shown that by controlling the thermodynamics of the growth process, the structure and density of GB in the ReS2 domain can be tailored. First‐principles calculations point to interesting new properties resulting from such GBs, such as a new electron state or ferromagnetism, which are highly sought after in the construction of novel 2D devices.
Published in: "Advanced Functional Materials".
Nanoassembly growth model of low‐symmetry 2D materials is revealed to understand the formation mechanism of grain boundary and subdomain in CVD‐grown 1T′ ReS2. The controlled construct of diverse grain boundary structures combined with their novel properties will open up new prospects for the grain boundary‐mediated engineering of material properties and applications. Abstract Grain boundaries (GBs) significantly affect the electrical, optical, magnetic, and mechanical properties of 2D materials. An anisotropic 2D material like ReS2 provides unprecedented opportunities to explore novel GB properties, since the reduced lattice symmetry offers greater degrees of freedom to build new GB structures. Here the atomic structure and formation mechanism of unusual multidomain and diverse GB structures in the vapor phase synthesized ReS2 atomic layers are reported. Using high‐resolution electron microscopy, two major categories of GBs are observed in each ReS2 domain, namely, the joint GB including three structures, and the GBs formed from a reconstruction of Re4‐chains including seven different structures. Based on the experimental observations, a novel “nanoassembly growth model” is proposed to elucidate the growth process of ReS2, where three types of Re4‐chain reconstruction give rise to a multidomain structure. Moreover, it is shown that by controlling the thermodynamics of the growth process, the structure and density of GB in the ReS2 domain can be tailored. First‐principles calculations point to interesting new properties resulting from such GBs, such as a new electron state or ferromagnetism, which are highly sought after in the construction of novel 2D devices.
Published in: "Advanced Functional Materials".
Nanoassembly growth model of low‐symmetry 2D materials is revealed to understand the formation mechanism of grain boundary and subdomain in CVD‐grown 1T′ ReS2. The controlled construct of diverse grain boundary structures combined with their novel properties will open up new prospects for the grain boundary‐mediated engineering of material properties and applications. Abstract Grain boundaries (GBs) significantly affect the electrical, optical, magnetic, and mechanical properties of 2D materials. An anisotropic 2D material like ReS2 provides unprecedented opportunities to explore novel GB properties, since the reduced lattice symmetry offers greater degrees of freedom to build new GB structures. Here the atomic structure and formation mechanism of unusual multidomain and diverse GB structures in the vapor phase synthesized ReS2 atomic layers are reported. Using high‐resolution electron microscopy, two major categories of GBs are observed in each ReS2 domain, namely, the joint GB including three structures, and the GBs formed from a reconstruction of Re4‐chains including seven different structures. Based on the experimental observations, a novel “nanoassembly growth model” is proposed to elucidate the growth process of ReS2, where three types of Re4‐chain reconstruction give rise to a multidomain structure. Moreover, it is shown that by controlling the thermodynamics of the growth process, the structure and density of GB in the ReS2 domain can be tailored. First‐principles calculations point to interesting new properties resulting from such GBs, such as a new electron state or ferromagnetism, which are highly sought after in the construction of novel 2D devices.
Published in: "Advanced Functional Materials".
Polarized Raman spectroscopy on few-layer ReS2 and ReSe2 was carried out to determine the crystallographic orientations. Since monolayer ReX2 (X=S or Se) has a distorted trigonal structure with only an inversion center, there is in-plane anisotropy and the two faces of a monolayer crystal are not equivalent. Since many physical properties vary sensitively depending on the crystallographic orientation, it is important to develop a reliable method to determine the crystal axes of ReX2. By comparing the relative polarization dependences of some representative Raman modes measured with three different excitation laser energies with high-resolution scanning transmission electron microscopy, we established a reliable procedure to determine the all three principal directions of few-layer ReX2 including a way to distinguish the two types of faces: a 2.41-eV laser for ReS2 or a 1.96-eV laser for ReSe2 should be chosen as the excitation source of polarized Raman measurements; then the relative directions of the maximum intensity polarization of the Raman modes at 151 and 212 cm-1 (124 and 161 cm-1) of ReS2 (ReSe2) can be used to determine the face types and the Re-chain direction unambiguously.
Published : "arXiv Mesoscale and Nanoscale Physics".
In article number https://doi.org/10.1002/aenm.2019011461901146, Naiqin Zhao, Shi‐Zhang Qiao and co‐workers confine 1T’‐ReS2 in 2D‐honeycombed carbon nanosheets for sodium‐ion battery anodes. The intended 2D‐honeycombed carbon protective layer and the strong interfacial interaction contribute to the ultra‐stable long‐term cycling and high rate performance.
Published in: "Advanced Energy Materials".
npj 2D Materials and Applications, Published online: 08 May 2019; doi:10.1038/s41699-019-0102-xPressure dependence of direct optical transitions in ReS2 and ReSe2
Published in: "NPJ 2D Materials and Applications".
1T′‐ReS2 confined in 2D‐honeycombed carbon nanosheets is reported as a promising sodium‐ion battery anode with ultra‐stable long term cycling and high rate performance. High rate performance is attributed to strong interfacial interaction between carbon and ReS2 and the intended 2D‐honeycombed carbon protective layer. Findings are corroborated by advanced characterization techniques and theoretical calculations. Abstract ReS2 (rhenium disulfide) is a new transition‐metal dichalcogenide that exhibits 1T′ phase and extremely weak interlayer van der Waals interactions. This makes it promising as an anode material for sodium‐ion batteries. However, achieving both a high‐rate capability and a long‐life has remained a major research challenge. Here, a new composite is reported, in which both are realized for the first time. 1T′‐ReS2 is confined through strong interfacial interaction in a 2D‐honeycombed carbon nanosheets that comprise an rGO inter‐layer and a N‐doped carbon coating‐layer (rGO@ReS2@N‐C). The strong interfacial interaction between carbon and ReS2 increases overall conductivity and decreases Na+ diffusion resistance, whilst the intended 2D‐honeycombed carbon protective layer maintains structural morphology and electrochemical activity during long‐term cycling. These findings are confirmed by advanced characterization techniques, electrochemical measurement, and density functional theory calculation. The new rGO@ReS2@N‐C exhibits the greatest rate performance reported so far for ReS2 of 231 mAh g−1 at 10 A g−1. Significantly, this is together with ultra‐stable long‐term cycling of 192 mAh g−1 at 2 A g−1 after 4000 cycles.
Published in: "Advanced Energy Materials".
1T′‐ReS2 confined in 2D‐honeycombed carbon nanosheets is reported as a promising sodium‐ion battery anode with ultra‐stable long term cycling and high rate performance. High rate performance is attributed to strong interfacial interaction between carbon and ReS2 and the intended 2D‐honeycombed carbon protective layer. Findings are corroborated by advanced characterization techniques and theoretical calculations. Abstract ReS2 (rhenium disulfide) is a new transition‐metal dichalcogenide that exhibits 1T′ phase and extremely weak interlayer van der Waals interactions. This makes it promising as an anode material for sodium‐ion batteries. However, achieving both a high‐rate capability and a long‐life has remained a major research challenge. Here, a new composite is reported, in which both are realized for the first time. 1T′‐ReS2 is confined through strong interfacial interaction in a 2D‐honeycombed carbon nanosheets that comprise an rGO inter‐layer and a N‐doped carbon coating‐layer (rGO@ReS2@N‐C). The strong interfacial interaction between carbon and ReS2 increases overall conductivity and decreases Na+ diffusion resistance, whilst the intended 2D‐honeycombed carbon protective layer maintains structural morphology and electrochemical activity during long‐term cycling. These findings are confirmed by advanced characterization techniques, electrochemical measurement, and density functional theory calculation. The new rGO@ReS2@N‐C exhibits the greatest rate performance reported so far for ReS2 of 231 mAh g−1 at 10 A g−1. Significantly, this is together with ultra‐stable long‐term cycling of 192 mAh g−1 at 2 A g−1 after 4000 cycles.
Published in: "Advanced Energy Materials".