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1.
Nano Lett ; 19(11): 8155-8160, 2019 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-31603685

RESUMO

Thermal transport across interfaces depends on the matching of vibrational structure at the interface. This work examines the transfer of thermal excitation from an organic ligand coating to either all-inorganic cesium lead tribromide (CsPbBr3) nanocrystals or hybrid organic-inorganic formamidinium lead tribromide (FAPbBr3) nanocrystals using selective infrared optical excitation. These two semiconductors are directly compared because they (or similar semiconductors) are currently envisioned as strong candidates in many optoelectronic technologies and they differ due to the presence of an organic or inorganic cation, which introduces substantial differences in the phonon density of states in otherwise quite similar semiconductors. Infrared excitation of C-H vibrations of surface-bound ligands generates a temperature gradient between the organic ligand shell and nanocrystal core, which results in heat flow, measured by probing changes of the semiconductor band gap. Heat transfer to both perovskite compositions of comparable sizes is similar (25-30 ps), due to fast intramolecular vibrational relaxation and similar matching of low-energy phonons with the organic ligand, but FAPbBr3 samples show a slow bleaching kinetic on the order of 1 ns. This slow, heat-induced change in the semiconductor band gap is attributed not to interfacial heat transfer but instead to thermal equilibration between the organic and inorganic sublattices of FAPbBr3. Ab initio molecular dynamics simulations support the hypothesis that low-energy inorganic sublattice phonon modes are populated initially in the heat transfer process, with a slow thermal population of the higher-energy phonon modes associated primarily with the organic cation. Slow thermal equilibration of FAPbBr3 is likely to substantially impact the time-dependent response of optoelectronic devices that heat the semiconductor active layer and provide further evidence that the poor bulk thermal transport of hybrid perovskite materials extends to microscopic thermal processes.

2.
Nanoscale ; 11(31): 14698-14706, 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31343043

RESUMO

Two-dimensional (2D) materials provide a plethora of novel condensed matter physics and are the new playground in materials science, offering potentially vast applications. One of the critical hurdles for many 2D systems is the synthesis of these low-dimensional systems as well as the prediction and identification of new candidates. Herein, a self-assembly of a monolayer tellurene by bonding CdTe wafers is demonstrated for the first time. The conventional applications of wafer-bonding range from the production of microelectromechanical systems to the synthesis of lattice-mismatched multi-junction photovoltaics. Due to the heterogeneous materials that are typically employed, the bond-interface usually contains a thin amorphous layer or arrays of dislocations. Such an interface is thus itself inactive and in many cases has detrimental effects on the device. The new material phase stabilized in this work consists of an undulating monolayer of tellurium atoms covalently bonded to {111} Cd-terminated CdTe wafer surfaces. First-principles calculations and experimentally observed changes in the localized plasmon excitation energy indicate the clear rearrangement of the underlying band-structure suggesting a metallic character, bands showing linear dispersion, and a significant asymmetric spin-band splitting. The I-V characteristics show the presence of a highly conductive pathway that lowers the resistivity by three orders of magnitude, as compared to bulk CdTe, which can be attributed to the tellurium monolayer. The findings indicate that suitably chosen crystallographic wafer surfaces can act as structural templates allowing the production of exotic phases. The presently stabilized monolayer is an addition to the family of tellurene variants, providing new insights into the fundamental properties of this and other emerging 2D materials, while attracting attention to the unusual side of the wafer-bonding technology exemplified in this study.

3.
Nanoscale ; 11(22): 10756-10762, 2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31120466

RESUMO

Employing electrons for direct control of a nanoscale reaction is highly desirable since it enables fabrication of nanostructures with different properties at atomic resolution and with flexibility of dimensions and location. Here, applying in situ transmission electron microscopy, we show the reversible oxidation and reduction kinetics in Ag, well controlled by changing the dose rate of the electron beam. Aberration-corrected high-resolution transmission electron microscopy observation reveals that O atoms are preferably inserted and extracted along the {111} close-packed planes of Ag, leading to the nucleation and decomposition of nanoscale Ag2O islands on the Ag substrate. By controlling the electron beam size and dose rate, we demonstrated the fabrication of an array of 3 nm Ag2O nanodots in an Ag matrix. Our results open a new pathway to manipulate an atomistic reaction with an electron beam towards the precise fabrication of nanostructures for device applications.

4.
ACS Nano ; 13(7): 7825-7832, 2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31117380

RESUMO

Oxide conversion reactions are known to have substantially higher specific capacities than intercalation materials used in Li-ion batteries, but universally suffer from large overpotentials associated with the formation of interfaces between the resulting nanoscale metal and Li2O products. Here we use the interfacial sensitivity of operando X-ray reflectivity to visualize the structural evolution of ultrathin NiO electrodes and their interfaces during conversion. We observe two additional reactions prior to the well-known bulk, three-dimensional conversion occurring at 0.6 V: an accumulation of lithium at the buried metal/oxide interface (at 2.2 V) followed by interfacial lithiation of the buried NiO/Ni interface at the theoretical potential for conversion (at 1.9 V). To understand the mechanisms for bulk and interfacial lithiation, we calculate interfacial energies using density functional theory to build a potential-dependent nucleation model for conversion. These calculations show that the additional space charge layer of lithium is a crucial component for reducing energy barriers for conversion in NiO.

5.
ACS Appl Mater Interfaces ; 11(9): 9583-9593, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-30789701

RESUMO

Lead halide perovskites present a versatile class of solution-processable semiconductors with highly tunable bandgaps that span ultraviolet, visible, and near-infrared portions of the spectrum. We explore phase-separated chloride and iodide lead perovskite mixtures as candidate materials for intermediate band applications in future photovoltaics. X-ray diffraction and scanning electron microscopy reveal that deposition of precursor solutions across the MAPbCl3/MAPbI3 composition space affords quasi-epitaxial cocrystallized films, in which the two perovskites do not alloy but instead remain phase-segregated. First-principle calculations further support the formation of an epitaxial interface and predict energy offsets in the valence band and conduction band edges that could result in intermediate energy absorption. The charge dynamics of variable mixtures of the relatively narrow bandgap (1.57 eV) MAPbI3 perovskite and wide bandgap (3.02 eV) MAPbCl3 are probed to map charge and energy flow direction and kinetics. Time-resolved photoluminescence and transient absorption measurements reveal charge transfer of photoexcited carriers in MAPbCl3 to MAPbI3 in tens of picoseconds. The rate of quenching can be further tuned by replacing MAPbI3 with two-dimensional Ruddlesden-Popper (BA)2(MA) n-1Pb nI3 n+1 ( n = 3, 2, and 1) perovskites, which also remain phase-separated.

6.
J Phys Chem Lett ; 10(4): 806-812, 2019 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-30615467

RESUMO

Harnessing oxygen redox reactions is an intriguing route to increasing capacity in Li-ion batteries (LIBs). Despite numerous experimental and theoretical attempts to unravel the mechanism of oxygen redox behavior, the electronic origin of oxygen activities in energy storage of Li-rich LIB materials remains under intense debate. In this work, the onset of oxygen activity was examined using a Li-rich material that has been reported to exhibit oxygen redox, namely, Li5FeO4. By comparing experimental measurements and first-principles Bethe-Salpeter equation calculations of oxygen K-edge X-ray absorption spectra (XAS), it was found that experimentally-observed changes in XAS originate from the nonbonding oxygen states in cation-disordered delithiated Li5FeO4, and the spectral features of oxygen dimers were also determined. This combined experimental and theoretical study offers an effective approach to disentangle the intertwined signals in XAS and can be further utilized in broader contexts for characterizing other energy storage and conversion materials.

7.
Nat Commun ; 10(1): 482, 2019 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-30696817

RESUMO

Organic-inorganic hybrid perovskites such as methylammonium lead iodide (CH3NH3PbI3) are game-changing semiconductors for solar cells and light-emitting devices owing to their defect tolerance and exceptionally long carrier lifetimes and diffusion lengths. Determining whether the dynamically disordered organic cations with large dipole moment benefit the optoelectronic properties of CH3NH3PbI3 has been an outstanding challenge. Herein, via transient absorption measurements employing an infrared pump pulse tuned to a methylammonium vibration, we observe slow, nanosecond-long thermal dissipation from the selectively excited organic mode to the inorganic sublattice. The resulting transient electronic signatures, during the period of thermal-nonequilibrium when the induced thermal motions are mostly concentrated on the organic sublattice, reveal that the induced atomic motions of the organic cations do not alter the absorption or the photoluminescence response of CH3NH3PbI3, beyond thermal effects. Our results suggest that the attractive optoelectronic properties of CH3NH3PbI3 mainly derive from the inorganic lead-halide framework.

8.
Phys Chem Chem Phys ; 20(43): 27456-27463, 2018 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-30357202

RESUMO

Cuprous oxide (Cu2O) is a promising catalyst for several important reactions. However, the atomic structures of defective Cu2O surfaces, which critically affect the catalytic properties both thermodynamically and kinetically, are not unambiguously characterized. High-resolution scanning tunneling microscopy (STM), combined with density functional theory (DFT) calculations and STM simulations, has been used to determine the atomic structure of the (111) surface of a Cu2O bulk crystal. The single crystal surface, processed by ultrahigh vacuum cleaning and oxygen annealing, shows a (1 × 1) periodicity in the low-energy electron diffraction pattern. The pristine (defect-free) Cu2O(111) surface exhibits a lattice of protrusions with hexagonal symmetry under STM, which is attributed to the dangling bonds of the coordinatively unsaturated copper (CuU) atoms on the surface. Two types of surface atomic defects are also identified, including the CuU vacancy and the oxygen-vacancy-induced local surface restructuring. The electronic structure of this surface measured by dI/dV spectroscopy shows an energy band gap of ∼1.6-2.1 eV. Consistent with dI/dV measurements, DFT calculations identified surface states within the electronic band gap arising from the Cu ions on the surface. Our results provide a clear picture of the pristine and defective Cu2O(111) surface structure in addition to the formation mechanism of the reconstructed surface, paving the way toward studying the site-dependent reactivity of this surface.

9.
Nat Commun ; 9(1): 2792, 2018 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-30022022

RESUMO

Hybrid organic-inorganic perovskites are emerging semiconductors for cheap and efficient photovoltaics and light-emitting devices. Different from conventional inorganic semiconductors, hybrid perovskites consist of coexisting organic and inorganic sub-lattices, which present disparate atomic masses and bond strengths. The nanoscopic interpenetration of these disparate components, which lack strong electronic and vibrational coupling, presents fundamental challenges to the understanding of charge and heat dissipation. Here we study phonon population and equilibration processes in methylammonium lead iodide (MAPbI3) by transiently probing the vibrational modes of the organic sub-lattice following above-bandgap optical excitation. We observe inter-sub-lattice thermal equilibration on timescales ranging from hundreds of picoseconds to a couple of nanoseconds. As supported by a two-temperature model based on first-principles calculations, the slow thermal equilibration is attributable to the sequential phonon populations of the inorganic and organic sub-lattices, respectively. The observed long-lasting thermal non-equilibrium offers insights into thermal transport and heat management of the emergent hybrid material class.

10.
ACS Nano ; 12(5): 4938-4945, 2018 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-29715007

RESUMO

Memristive devices are an emerging technology that enables both rich interdisciplinary science and novel device functionalities, such as nonvolatile memories and nanoionics-based synaptic electronics. Recent work has shown that the reproducibility and variability of the devices depend sensitively on the defect structures created during electroforming as well as their continued evolution under dynamic electric fields. However, a fundamental principle guiding the material design of defect structures is still lacking due to the difficulty in understanding dynamic defect behavior under different resistance states. Here, we unravel the existence of threshold behavior by studying model, single-crystal devices: resistive switching requires that the pristine oxygen vacancy concentration reside near a critical value. Theoretical calculations show that the threshold oxygen vacancy concentration lies at the boundary for both electronic and atomic phase transitions. Through operando, multimodal X-ray imaging, we show that field tuning of the local oxygen vacancy concentration below or above the threshold value is responsible for switching between different electrical states. These results provide a general strategy for designing functional defect structures around threshold concentrations to create dynamic, field-controlled phases for memristive devices.

11.
Chem Mater ; 302018.
Artigo em Inglês | MEDLINE | ID: mdl-31080315

RESUMO

Balancing global energy needs against increasing greenhouse gas emissions requires new methods for efficient CO2 reduction. While photoreduction of CO2 is promising, the rational design of photocatalysts hinges on precise characterization of the surface catalytic reactions. Cu2O is a promising next-generation photocatalyst, but the atomic-scale description of the interaction between CO2 and the Cu2O surface is largely unknown, and detailed experimental measures are lacking. In this study, density-functional theory (DFT) calculations have been performed to identify the Cu2O (110) surface stoichiometry that favors CO2 reduction. To facilitate interpretation of scanning tunneling microscopy (STM) and X-ray absorption near-edge structures (XANES) measurements, which are useful for characterizing catalytic reactions, we present simulations based on DFT-derived surface morphologies with various adsorbate types. STM and XANES simulations were performed using the Tersoff-Hamann approximation and Bethe-Salpeter equation (BSE) approach, respectively. The results provide guidance for observation of CO2 reduction reaction on, and rational surface engineering of, Cu2O (110). They also demonstrate the effectiveness of computational image and spectroscopy modeling as a predictive tool for surface catalysis characterization.

12.
Nanoscale ; 9(46): 18229-18239, 2017 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-29043353

RESUMO

A fundamental understanding of the inter-relationships between structure, morphology, atomic scale dynamics, chemistry, and physical properties of mixed metallic-covalent systems is essential to design novel functional materials for applications in flexible nano-electronics, energy storage and catalysis. To achieve such knowledge, it is imperative to develop robust and computationally efficient atomistic models that describe atomic interactions accurately within a single framework. Here, we present a unified Tersoff-Brenner type bond order potential (BOP) for a Co-C system, trained against lattice parameters, cohesive energies, equation of state, and elastic constants of different crystalline phases of cobalt as well as orthorhombic Co2C derived from density functional theory (DFT) calculations. The independent BOP parameters are determined using a combination of supervised machine learning (genetic algorithms) and local minimization via the simplex method. Our newly developed BOP accurately describes the structural, thermodynamic, mechanical, and surface properties of both the elemental components as well as the carbide phases, in excellent accordance with DFT calculations and experiments. Using our machine-learnt BOP potential, we performed large-scale molecular dynamics simulations to investigate the effect of metal/carbon concentration on the structure and mechanical properties of porous architectures obtained via self-assembly of cobalt nanoparticles and fullerene molecules. Such porous structures have implications in flexible electronics, where materials with high electrical conductivity and low elastic stiffness are desired. Using unsupervised machine learning (clustering), we identify the pore structure, pore-distribution, and metallic conduction pathways in self-assembled structures at different C/Co ratios. We find that as the C/Co ratio increases, the connectivity between the Co nanoparticles becomes limited, likely resulting in low electrical conductivity; on the other hand, such C-rich hybrid structures are highly flexible (i.e., low stiffness). The BOP model developed in this work is a valuable tool to investigate atomic scale processes, structure-property relationships, and temperature/pressure response of Co-C systems, as well as design organic-inorganic hybrid structures with a desired set of properties.

13.
J Chem Theory Comput ; 13(9): 4492-4503, 2017 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-28800233

RESUMO

Machine learning (ML) techniques with the genetic algorithm (GA) have been applied to determine a polarizable force field parameters using only ab initio data from quantum mechanics (QM) calculations of molecular clusters at the MP2/6-31G(d,p), DFMP2(fc)/jul-cc-pVDZ, and DFMP2(fc)/jul-cc-pVTZ levels to predict experimental condensed phase properties (i.e., density and heat of vaporization). The performance of this ML/GA approach is demonstrated on 4943 dimer electrostatic potentials and 1250 cluster interaction energies for methanol. Excellent agreement between the training data set from QM calculations and the optimized force field model was achieved. The results were further improved by introducing an offset factor during the machine learning process to compensate for the discrepancy between the QM calculated energy and the energy reproduced by optimized force field, while maintaining the local "shape" of the QM energy surface. Throughout the machine learning process, experimental observables were not involved in the objective function, but were only used for model validation. The best model, optimized from the QM data at the DFMP2(fc)/jul-cc-pVTZ level, appears to perform even better than the original AMOEBA force field (amoeba09.prm), which was optimized empirically to match liquid properties. The present effort shows the possibility of using machine learning techniques to develop descriptive polarizable force field using only QM data. The ML/GA strategy to optimize force fields parameters described here could easily be extended to other molecular systems.

14.
Phys Rev Lett ; 119(13): 136602, 2017 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-29341683

RESUMO

We compute the transient dynamics of phonons in contact with high energy "hot" charge carriers in 12 polar and nonpolar semiconductors, using a first-principles Boltzmann transport framework. For most materials, we find that the decay in electronic temperature departs significantly from a single-exponential model at times ranging from 1 to 15 ps after electronic excitation, a phenomenon concomitant with the appearance of nonthermal vibrational modes. We demonstrate that these effects result from slow thermalization within the phonon subsystem, caused by the large heterogeneity in the time scales of electron-phonon and phonon-phonon interactions in these materials. We propose a generalized two-temperature model accounting for phonon thermalization as a limiting step of electron-phonon thermalization, which captures the full thermal relaxation of hot electrons and holes in semiconductors. A direct consequence of our findings is that, for semiconductors, information about the spectral distribution of electron-phonon and phonon-phonon coupling can be extracted from the multiexponential behavior of the electronic temperature.

15.
Sci Rep ; 6: 34974, 2016 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-27892462

RESUMO

Au nanoclusters are of technological relevance for catalysis, photonics, sensors, and of fundamental scientific interest owing to planar to globular structural transformation at an anomalously high number of atoms i.e. in the range 12-14. The nature and causes of this transition remain a mystery. In order to unravel this conundrum, high throughput density functional theory (DFT) calculations, coupled with a global structural optimization scheme based on a modified genetic algorithm (GA) are conducted. More than 20,000 Au12, Au13, and Au14 nanoclusters are evaluated. With any DFT functional, globular and planar structures coexist across the size range of interest. The planar-globular transition is gradual at room temperature rather than a sharp transition as previously believed. The effects of anionicity, s-d band hybridization and long range interactions on the dimensional transition are quantified by using the structures adjacent to the minima. Anionicity marginally changes the relative stability of the clusters. The degree of s-d hybridization is varied via changing the Hubbard U value which corroborate that s-d hybridization alone does not stabilize planar structures. van der Waals interactions, on the other hand, stabilize globular structures. These results elucidate the balance between the different reasons of the dimensional transition in gold nanoclusters.

16.
J Phys Chem Lett ; 7(19): 3752-3759, 2016 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-27569053

RESUMO

We introduce a bond order potential (BOP) for stanene based on an ab initio derived training data set. The potential is optimized to accurately describe the energetics, as well as thermal and mechanical properties of a free-standing sheet, and used to study diverse nanostructures of stanene, including tubes and ribbons. As a representative case study, using the potential, we perform molecular dynamics simulations to study stanene's structure and temperature-dependent thermal conductivity. We find that the structure of stanene is highly rippled, far in excess of other 2-D materials (e.g., graphene), owing to its low in-plane stiffness (stanene: ∼ 25 N/m; graphene: ∼ 480 N/m). The extent of stanene's rippling also shows stronger temperature dependence compared to that in graphene. Furthermore, we find that stanene based nanostructures have significantly lower thermal conductivity compared to graphene based structures owing to their softness (i.e., low phonon group velocities) and high anharmonic response. Our newly developed BOP will facilitate the exploration of stanene based low dimensional heterostructures for thermoelectric and thermal management applications.

17.
Sci Rep ; 6: 27009, 2016 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-27255415

RESUMO

Extended defects are of considerable importance in determining the electronic properties of semiconductors, especially in photovoltaics (PVs), due to their effects on electron-hole recombination. We employ model systems to study the effects of dislocations in CdTe by constructing grain boundaries using wafer bonding. Atomic-resolution scanning transmission electron microscopy (STEM) of a [1-10]/(110) 4.8° tilt grain boundary reveals that the interface is composed of three distinct types of Lomer dislocations. Geometrical phase analysis is used to map strain fields, while STEM and density functional theory (DFT) modeling determine the atomic structure at the interface. The electronic structure of the dislocation cores calculated using DFT shows significant mid-gap states and different charge-channeling tendencies. Cl-doping is shown to reduce the midgap states, while maintaining the charge separation effects. This report offers novel avenues for exploring grain boundary effects in CdTe-based solar cells by fabricating controlled bicrystal interfaces and systematic atomic-scale analysis.

18.
ACS Nano ; 10(3): 3738-46, 2016 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-26937679

RESUMO

Operando characterization of gas-solid reactions at the atomic scale is of great importance for determining the mechanism of catalysis. This is especially true in the study of heterostructures because of structural correlation between the different parts. However, such experiments are challenging and have rarely been accomplished. In this work, atomic scale redox dynamics of Ag/AgCl heterostructures have been studied using in situ environmental transmission electron microscopy (ETEM) in combination with density function theory (DFT) calculations. The reduction of Ag/AgCl to Ag is likely a result of the formation of Cl vacancies while Ag(+) ions accept electrons. The oxidation process of Ag/AgCl has been observed: rather than direct replacement of Cl by O, the Ag/AgCl nanocatalyst was first reduced to Ag, and then Ag was oxidized to different phases of silver oxide under different O2 partial pressures. Ag2O formed at low O2 partial pressure, whereas AgO formed at atmospheric pressure. By combining in situ ETEM observation and DFT calculations, this structural evolution is characterized in a distinct nanoscale environment.

19.
ACS Appl Mater Interfaces ; 7(34): 18985-96, 2015 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-26255641

RESUMO

The formation mechanism and composition of the solid electrolyte interphase (SEI) in lithium ion batteries has been widely explored. However, relatively little is known about the function of the SEI as a transport medium. Such critical information is directly relevant to battery rate performance, power loss, and capacity fading. To partially bridge this gap in the case of inorganic SEI compounds, we report herein the results of first-principles calculations on the defect thermodynamics, the dominant diffusion carriers, and the diffusion pathways associated with crystalline LiF and NaF, which are stable components of the SEI in Li-ion and Na-ion batteries, respectively. The thermodynamics of common point defects are computed, and the dominant diffusion carriers are determined over a voltage range of 0-4 V, corresponding to conditions relevant to both anode and cathode SEI's. Our analyses reveal that for both compounds, vacancy defects are energetically more favorable, therefore form more readily than interstitials, due to the close-packed nature of the crystal structures. However, the vacancy concentrations are very small for the diffusion processes facilitated by defects. Ionic conductivities are calculated as a function of voltage, considering the diffusion carrier concentration and the diffusion barriers as determined by nudged elastic band calculations. These conductivities are more than ten orders of magnitude smaller in NaF than in LiF. As compared to the diffusivity of Li in other common inorganic SEI compounds, such as Li2CO3 and Li2O, the cation diffusivity in LiF and NaF is quite low, with at least three orders of magnitude lower ionic conductivities. The results quantify the extent to which fluorides pose rate limitations in Li and Na batteries.

20.
Nat Commun ; 6: 7493, 2015 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-26138031

RESUMO

Layered molybdenum disulfide has demonstrated great promise as a low-cost alternative to platinum-based catalysts for electrochemical hydrogen production from water. Research effort on this material has focused mainly on synthesizing highly nanostructured molybdenum disulfide that allows the exposure of a large fraction of active edge sites. Here we report a promising microwave-assisted strategy for the synthesis of narrow molybdenum disulfide nanosheets with edge-terminated structure and a significantly expanded interlayer spacing, which exhibit striking kinetic metrics with onset potential of -103 mV, Tafel slope of 49 mV per decade and exchange current density of 9.62 × 10(-3) mA cm(-2), performing among the best of current molybdenum disulfide catalysts. Besides benefits from the edge-terminated structure, the expanded interlayer distance with modified electronic structure is also responsible for the observed catalytic improvement, which suggests a potential way to design newly advanced molybdenum disulfide catalysts through modulating the interlayer distance.

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