RESUMEN
Recently, layered SnSe2 has drawn broad research interest as a promising thermoelectric material that possesses great potential for application in energy conversion. However, extensive efforts have been devoted to optimizing the thermoelectric performance of SnSe2, but the ZT value is still far from satisfactory. Therefore, we developed an organic-inorganic superlattice hybrid by intercalating organic cations into SnSe2 interlayers in an attempt to enhance the thermoelectric properties. Organic intercalants can enlarge the basal spacing and decouple the SnSe2 layers, bringing about synergistic electrical transport modification and phonon softening. Thus, by simultaneously improving the electrical conductivity and reducing the thermal conductivity, a ZT value of 0.34 is achieved at 342 K in tetrabutylammonium-intercalated SnSe2, approximately two orders of magnitude higher than that of pristine SnSe2 single crystals. In addition, by opening van der Waals gaps via organic cations, outstanding flexibility of organic-intercalated SnSe2 is realized, with a superior figure of merit for flexibility of approximately 0.068. This work demonstrates a general and facile strategy to fabricate organic-inorganic superlattice hybrids with a considerable improvement in the thermoelectric performance via organic cation intercalation, which is promising for flexible thermoelectrics.
RESUMEN
Raman spectroscopy is a powerful technique to probe structural and doping behaviors of two-dimensional (2D) materials. In MoS2, the always coexisting in-plane (E2g1) and out-of-plane (A1g) vibrational modes are used as reliable fingerprints to distinguish the number of layers, strains, and doping levels. In this work, however, we report an abnormal Raman behavior, i.e., the absence of the A1g mode in cetyltrimethylammonium bromide (CTAB)-intercalated MoS2 superlattice. This unusual behavior is quite different from the softening of the A1g mode induced by surface engineering or electric-field gating. Interestingly, under a strong laser illumination, heating, or mechanical indentation, an A1g peak gradually appears, accompanied by the migration of intercalated CTA+ cations. The abnormal Raman behavior is mainly attributed to the constraint of the out-of-plane vibration due to intercalations and resulting severe electron doping. Our work renews the understanding of Raman spectra of 2D semiconducting materials and sheds light on developing next-generation devices with tunable structures.
RESUMEN
To mitigate the energy crisis and environmental pollution, efficient and earth-abundant hydrogen evolution reaction (HER) electrocatalysts are essential for hydrogen production through electrochemical water splitting. Graphene-based materials as metal-free catalysts have attracted significant attention but suffer from insufficient activity and stability. Therefore, a novel and economical approach is developed to prepare highly active, robust, and self-supported reduced graphene oxide (rGO)/SiO2 ceramic composites as electrocatalysts in HER. Through intercalation and pressure sintering, the rGO sheets are parallelly aligned and embedded into a dense and chemically inert SiO2 matrix, ensuring the electrical conductivity and stability of the prepared composites. After directional cutting, the edges of the oriented rGO sheets become fully exposed on the composite surface, acting as highly electrocatalytic active sites in HER, as confirmed by density functional theory calculations. The 4 vol% rGO/SiO2 composite displays superior electrocatalytic performance, featuring a low overpotential (134 mV) at a current density of 10 mA cm-2 , a small Tafel slope (103 mV dec-1 ), and excellent catalytic durability in 0.5 m H2 SO4 . This study provides a new yet cost-effective strategy to prepare metal-free, robust, and edge-rich rGO/ceramic composites as a highly electrocatalytic active catalyst for HER applications.
RESUMEN
Two-dimensional (2D) materials have received extensive interest due to their exceptional properties. It is strongly required to assemble 2D materials in bulk quantities for macroscopic applications, but this is highly restricted by the aggregation of 2D materials. Constructing three-dimensional (3D) hybrid superlattices of alternating 2D materials and organic molecule layers provides a new path to access the exceptional properties of 2D materials in bulk quantities. In this tutorial review, the emerging concept of hybrid inorganic/organic superlattices is systematically illustrated. The abundant compositions and the various structures of inorganic and organic sublattices in hybrid superlattices are presented, followed by a summary of the chemical interactions between them. Many facile techniques have been developed for hybrid superlattices, enabling precise control of the structure. There are also various interesting mechanisms inside unique hybrid inorganic/organic superlattices that can help tune the properties, including electron transfer, quantum confinement, interlayer coupling, multiple interface effects, etc. The rich chemistry and abundant mechanisms of these hybrid superlattices can enhance the performance beyond the reach of existing materials, and provide new opportunities in various applications, including rechargeable batteries, catalysis, thermoelectrics, advanced electronics, superconductors, optoelectronics, etc.
RESUMEN
TaS2 nanolayers with reduced dimensionality show interesting physics, such as a gate-tunable phase transition and enhanced superconductivity, among others. Here, a solution-based strategy to fabricate a large-area foil of hybrid TaS2 /organic superlattice, where [TaS2 ] monolayers and organic molecules alternatively stack in atomic scale, is proposed. The [TaS2 ] layers are spatially isolated with remarkably weakened interlayer bonding, resulting in lattice vibration close to that of TaS2 monolayers. The foil also shows excellent mechanical flexibility together with a large electrical conductivity of 1.2 × 103 S cm-1 and an electromagnetic interference of 31 dB, among the highest values for solution-processed thin films of graphene and inorganic graphene analogs. The solution-based strategy reported herein can add a new dimension to manipulate the structure and properties of 2D materials and provide new opportunities for flexible nanoelectronic devices.
