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Tensile strain is intrinsic to monolayer crystals of transition metal disulfides such as Mo(W)S

Thermal runaways triggered by the oxygen release from oxide cathode materials pose a major safety concern for widespread application of lithium ion batteries. Utilizing in situ aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) at high temperatures, we show that oxygen release from Li

Ultrathin dual phase nanosheets consisting of alternating spinel Li

In this paper, we report the first direct chemical and imaging evidence of lithium-induced atomic ordering in amorphous TiO2 nanomaterials and propose new reaction mechanisms that contradict the many works in the published literature on the lithiation behavior of these materials. The lithiation process was conducted in situ inside an atomic resolution transmission electron microscope. Our results indicate that the lithiation started with the valence reduction of Ti4+ to Ti3+ leading to a LixTiO2 intercalation compound. The continued intercalation of Li ions in TiO2 nanotubes triggered an amorphous to crystalline phase transformation. The crystals were formed as nano-islands and identified to be Li2Ti2O4 with cubic structure (a = 8.375 A). The tendency for the formation of these crystals was verified with density functional theory (DFT) simulations. The size of the crystalline islands provides a characteristic length scale (∼5 nm) at which the atomic bonding configuration has been changed within a short ti...

Wafer-scale monolayer WS2 has been widely investigated. Here, we report a repeatable and low-cost one-step chemical vapor deposition method for the direct growth of a 4-in. monolayer WS2 film on a thermal oxide silicon wafer by using WO3 and H2S gas as precursors. H2S gas exhibits a high vulcanization ability and can effectively reduce the growth temperature of WS2 to 825 °C. The growth process follows a self-limiting growth to form a monolayer polycrystalline film, which is merged via many stable small-angle grain boundaries. The wafer-scale monolayer WS2 film shows uniform and high-quality electrical properties. This method helps promote the future production and application of wafer-scale monolayer sulfide.

A new type of layered metal phosphide InP3 with porous structure is prepared via high temperature and high pressure synthesis. And then layered porous InP3 nanoflakes are obtained by liquid phase exfoliation, demonstrating broad application prospects in flexible all-solid-state supercapacitors (ASSP). The InP3-ASSP possess outstanding electrochemical performances including high specific volumetric capacitance of 27.2 F cm−3, high power density of 632 W cm−3, high energy density of 3.78 mW h cm−3. Moreover, the as-prepared InP3-ASSP device can operate in a relatively wide temperature range (−25–75 °C), and exhibit excellent stretchability, flexibility and cycling stability. The present work provides a new opportunity for the development of new layered metal phosphide in the field of energy storage.

Layered germanium phosphide, which combines the advantages of both germanium and phosphorus, is believed to be a potential anode for sodium ion battery. Here, the sodium storage mechanism and electrochemical performance of layered germanium phosphide have been deeply investigated by advanced in-situ transmission electron microscopy technique combining half-cell testing. Dynamic reaction process reveals that individual layered germanium phosphide nanoflake undergoes total area expansion of 248% without any detectable fracture or cracking in sodiation. In contrast, germanium phosphide experiences multi-step reactions, i.e. intercalation and alloying, accompanied by sequentially forming NaxGeP (0

Recently, intrinsic ferromagnetism of layered van der Waals compounds (such as CrCl3, CrI3, and Cr2Ge2Te6) has received widespread attention. Herein, layered van der Waals heterostructure composites of two dimensional layered magnetic material CrCl3 and graphene nanosheets (GNSs) are facilely obtained and investigated as microwave absorption materials. The complex permittivity and complex permeability of heterostructure composites can be adjusted by modulating the mass ratio of GNS and CrCl3. The real part and imaginary part of permittivity increase with the increase in the mass fraction of GNS in composites, due to the high conductivity of GNS. Thus, dielectric loss is enhanced and originates from the Debye relaxation process and the interfacial polarization process. The minimum reflection loss (RL) of the CrCl3-GNS heterostructure composite with a GNS mass fraction of 40 wt. % can reach −46.2 dB at a microwave frequency of 10 GHz with a thickness of 1.9 mm. In addition, the RL less than −10 dB can be achieved at different frequencies with all thicknesses (1–5 mm). This work might provide the practical application of two dimensional layered magnetic materials as ultrahigh-performance microwave absorption materials.

In two-dimensional layered materials, layer number and stacking order have strong effects on the optical and electronic properties. Tungsten disulfide (WS2) crystal, as one important member among transition metal dichalcogenides, has been usually prepared in a layered 2H prototype structure with space group P63/mmc ([Formula: see text]) in spite of many other expected ones such as 3R. Here, we report simultaneous growth of 2H and 3R stacked multilayer (ML) WS2 crystals in large scale by chemical vapor deposition and effects of layer number and stacking order on optical and electronic properties. As revealed in Raman and photoluminescence (PL) measurements, with an increase in layer number, 2H and 3R stacked ML WS2 crystals show similar variation of PL and Raman peaks in position and intensity. Compared to 2H stacked ML WS2, however, 3R stacked one always exhibits the larger red (blue) shift of Raman [Formula: see text] (A1g) peak and the appearance of PL A, B and I peaks at lower energies. Thereby, PL and Raman features depend on not only layer number but also stacking order. In addition, circularly polarized luminescence from two prototype WS2 crystals under circularly polarized excitation has also been investigated, showing obvious spin or valley polarization of these CVD-grown multilayer WS2 crystals.

High efficiency, lightweight, and tunable microwave absorbing materials have drawn tremendous attention. Here, we have synthesized layered GeP5 bulk at high temperature and high pressure. Then, the GeP5 nanosheets are obtained by an efficient liquid-phase exfoliation method and display excellent microwave absorption performance as a microwave absorber. The reflection loss (RL) can achieve below −10 dB in a wide range of thicknesses and microwave frequencies. For further meeting the lightweight demand of microwave absorption materials, porous germanium (GeP5-570) is obtained from GeP5 via the annealing treatment. Microwave absorption characteristics can be significantly improved after annealing treatment. The minimum RL values of porous germanium (GeP5-570) can reach −37.8 dB at a microwave frequency of 4.7 GHz under a thickness of 2.9 mm. The effective absorption bandwidth (RL< −10 dB) of GeP5-570 is 11.8–14.3 GHz with a thickness of 1.2 mm. In addition, the RL value can attain −20 dB in the frequency range of 3.8–16.1 GHz with various thicknesses from 1.0 to 3.5 mm.

In situ high resolution transmission electron microscopy investigations were performed on sub-10-nm Au crystals. The effects of tensile loading direction and crystal size on the deformation mechanism of Au crystals were analysed. For the Au crystals with a width below 2 nm, the surface atom diffusion with a phenomenon of layer by layer peeling is the main deformation mechanism and the tensile loading direction plays negligible effect. For the Au crystals with a width over 7 nm, the dislocations generated form surface and gliding into crystal dominate the plastic deformation and the tensile loading direction plays important role. Lomer dislocations are produced and destructed by dislocation reaction during tensile strain process in oriented Au crystal. The Schmid law is the key intrinsic issue controlling the deformation mechanism for the nanowires with a size larger than 7 nm.

Black phosphorus (BP) has recently drawn great attention in the field of electrocatalysis due to its distinct electrocatalytic activity for the oxygen evolution reaction (OER). However, the slow OER kinetics and the poor environmental stability of BP seriously limits its overall OER performance and prevents its electrocatalysis application. Here, sulfur (S)-doped BP nanosheets, which are prepared using high-pressure synthesis followed by liquid exfoliation, have been demonstrated to have much better OER electrocatalytic activity and environmental stability compared to their undoped counterparts. The S-doped BP nanosheets display a Tafel slope of 75 mV dec-1, which is a favorable value refered to the kinetics of OER in electrochemical tests. Notably, there is no degradation of S-doped BP nanosheets after six days exposure to ambient, indicating an excellent environmental stability of the S-doped BP. The density functional theory calculations show that the OER activity of BP originate from its crystal defects and heteroatom S doping can effectively enhance its OER activity and stability. These results highlight the doping effect on electrocatalytic activities and stability of BP and provide a simple and effective method to design highly efficient OER catalysts based on the modification of BP.

Nanolayers of Al2O3 and TiO2 coatings were applied to lithium- and manganese-rich cathode powder Li1.2Ni0.13Mn0.54Co0.13O2 using an atomic layer deposition (ALD) method. The ALD coatings exhibited different surface morphologies; the Al2O3 surface film appeared to be uniform and conformal, while the TiO2 layers appeared as particulates across the material surface. In a Li-cell, the Al2O3 surface film was stable during repeated charge and discharge, and this improved the cell cycling stability, despite a high surface impedance. The TiO2 layer was found to be more reactive with Li and formed a LixTiO2 interface, which led to a slight increase in cell capacity. However, the repetitive insertion/extraction process for the Li+ ions caused erosion of the surface protective TiO2 film, which led to degradation in cell performance, particularly at high temperature. For cells comprised of the coated Li1.2Ni0.13Mn0.54Co0.13O2 and an anode of meso-carbon-micro-beads (MCMB), the cycling stability introduced by ALD was not enough to overcome the electrochemical instability of MCMB graphite. Therefore, protection of the cathode materials by ALD Al2O3 or TiO2 can address some of the capacity fading issues related to the Li-rich cathode at room temperature.

Despite many theoretical predictions indicating exceptionally low energy barriers of ionic transport in phosphorene, the ionic transport pathways in this two-dimensional (2D) material has not been experimentally demonstrated. Here, using in situ aberration-corrected transmission electron microscopy (TEM) and density functional theory, we studied sodium ion transport in phosphorene. Our high-resolution TEM imaging complemented by electron energy loss spectroscopy demonstrates a precise description of anisotropic sodium ions migration along the [100] direction in phosphorene. This work also provides new insight into the effect of surface and the edge sites on the transport properties of phosphorene. According to our observation, the sodium ion transport is preferred in zigzag edge rather than the armchair edge. The use of this highly selective ionic transport property may endow phosphorene with new functionalities for novel chemical device applications.

Controlled synthesis of nanomaterials is one of the grand challenges facing materials scientists. In particular, how tunnel-based nanomaterials aggregate during synthesis while maintaining their well-aligned tunneled structure is not fully understood. Here, we describe the atomistic mechanism of oriented attachment (OA) during solution synthesis of tunneled α-MnO2 nanowires based on a combination of in situ liquid cell transmission electron microscopy (TEM), aberration-corrected scanning TEM with subangstrom spatial resolution, and first-principles calculations. It is found that primary tunnels (1 × 1 and 2 × 2) attach along their common {110} lateral surfaces to form interfaces corresponding to 2 × 3 tunnels that facilitate their short-range ordering. The OA growth of α-MnO2 nanowires is driven by the stability gained from elimination of {110} surfaces and saturation of Mn atoms at {110}-edges. During this process, extra [MnOx] radicals in solution link the two adjacent {110} surfaces and bond with the unsaturated Mn atoms from both surface edges to produce stable nanowire interfaces. Our results provide insights into the controlled synthesis and design of nanomaterials in which tunneled structures can be tailored for use in catalysis, ion exchange, and energy storage applications.

To further advance our understanding of the mechanical behavior of nano-sized crystals, it is important to visualize the deformation process in the real material system. In this work, body-centered-tetragonal (BCT) lattice was observed during in-situ tension of gold nano-junction in a transmission electron microscope, which is well explained by the proposed deformation mechanism. In contrast to the well-known Bain model, the phase transformation can be realized by a progressively slipping process with a vector of 1/12 . The lattice constant a can be accurately predicated from a hard-sphere model and c is about 5% larger than that in MD simulations using a more realistic interatomic potential.

Catalysts V2O5/TiO2–carbon nanotubes (CNTs) were prepared by hydrothermal method and their activity for catalytic oxidation of chlorobenzene (CB) was studied. A CB conversion efficiency of 45% with a CO2 selectivity of 80% was achieved over V2O5 (1.2 wt %)/TiO2–CNTs(8.6 wt %) at a temperature as low as 200 °C. It also has the highest removal efficiency of 95% at 300 °C. From the analysis of XRD, SEM, TEM, and TPR, the low-temperature activity of V2O5/TiO2–CNTs could be ascribed to the high SBET, good dispersion of V2O5, and the possible adsorption of CB by free surface of CNTs.

A series of V2O5–MnOX/TiO2-CNTs, V2O5/TiO2-CNTs, and MnOX/TiO2-CNTs catalysts were synthesized via solvothermal method and their NOX removal activities were studied. A catalytic performance improvement was observed over catalysts prepared by mechanical mixing MnOX/TiO2-CNTs and V2O5/TiO2-CNTs. XRD, SEM, EDS, TPD, TPR, and BET were employed to analyze the improvement which is ascribed to the separation of Mn and V as well as the increase in reducibility and acidic strength. The existence of catalytic activity promotion between V2O5 and MnOX was clarified by TOF.

MnO x /Al2O3-carbon nanotubes (CNTs) composites prepared by hydrothermal method were characterized by XRD, SEM, TEM, TGA, BET, XPS and H2-TPR. Catalytic oxidation of chlorobenzene (CB) was conducted over the composites under gas hourly space velocity (GHSV) of 36000 h−1 and CB concentration of 2800 ppmv. For the catalyst with approximately 25 wt% CNTs and 10 at.% Mn, CB removal efficiencies reached up to 83.3 and 97.7% at 150 and 300 °C, respectively. Moreover, no Cl species was detected over the used MnO x /Al2O3-CNTs catalyst implying that the release of chlorine element from the catalyst surface was facilitated by CNTs introduction. MnOx/Al2O3-carbon nanotubes (CNTs) composites were prepared by hydrothermal method. Catalytic oxidation of chlorobenzene (CB) was conducted over the composites in a continuous fixed bed flow reactor. CB removal efficiencies at different temperatures were obtained over various catalysts with different CNTs concentrations under a gas space velocity of 36000 h−1 and CB concentration of 2800 ppmv. For the catalyst Mn/Al-C-2 with approximately 25 wt% CNTs and 10 at.% Mn, CB removal efficiencies of 83.3% at 150 °C and 97.7% at 300 °C were obtained. Our results suggest that the introduction of CNTs could significantly promote the catalytic oxidation of CB in low temperature region.

Nanostructure composites of ferromagnetic materials embedded in nanoporous carbon (NC) derived from metal-organic frameworks (MOFs) have attracted enormous attention due to their potential application in many fields, such as microwave absorption, energy storage, and conversion. The rational design of nanocomposites holds a determinant factor for overcoming the challenges involving the microwave absorption performance. Herein, CoS2/NC, CoP/NC, and CoS2-xPx/NC with a rhombic dodecahedral structure have been successfully fabricated by using the template cobalt-based MOFs (ZIF-67). A morphology analysis indicates that ferromagnetic nanoparticles are embedded in NC matrix. It is obvious that the rhombic dodecahedron can be maintained after the phosphorization and sulfurization of Co/NC derived from the thermal decomposition of ZIF-67. The microwave absorption performance can obviously be improved by the phosphorization and sulfurization of Co/NC. CoS2-xPx/NC exhibits an excellent microwave absorption property and the minimum reflection loss (RL) of CoS2-xPx/NC can reach -68 dB at 14.6 GHz with a thickness of 1.5 mm. An RL value less than -10 dB can be achieved in the microwave frequency range of 12.7-17.3 GHz (4.6 GHz) with a thickness of 1.5 mm for CoS2-xPx/NC. This article offers a novel way to fabricate cobalt-based materials/carbon composites for an excellent microwave absorber.

Centimeter-scale continuous monolayer WS2 film with large tensile strain has been successfully grown on oxidized silicon substrate by chemical vapor deposition, in which monolayer grains can be more than 200 μm in size. Monolayer WS2 grains are observed to merge together via not only traditional grain boundaries but also non-traditional ones, which are named as grain walls (GWs) due to their nanometer-scale widths. The GWs are revealed to consist of two or three layers. Though not a monolayer, the GWs exhibit significantly enhanced fluorescence and photoluminescence. This enhancement may be attributed to abundant structural defects such as stacking faults and partial dislocations in the GWs, which are clearly observable in atomically resolved high resolution transmission electron microscopy and scanning transmission electron microscopy images. Moreover, GW-based phototransistor is found to deliver higher photocurrent than that based on monolayer film. These features of GWs provide a clue to microstructure engineering of monolayer WS2 for specific applications in (opto)electronics.

Engineering silicon into nanostructures has been a well-adopted strategy to improve the cyclic performance of silicon as a lithium-ion battery anode. Here, we show that the electrode performance can be further improved by alloying silicon with germanium. We have evaluated the electrode performance of SixGe1−x nanoparticles (NPs) with different compositions. Experimentally, SixGe1−x NPs with compositions approaching Si50Ge50 are found to have better cyclic retention than both Si-rich and Ge-rich NPs. During the charge/discharge process, NP merging and Si-Ge homogenization are observed. In addition, a distinct morphology difference is observed after 100 cycles, which is believed to be responsible for the different capacity retention behavior. The present study on SixGe1−x alloy NPs sheds light on the development of Si-based electrode materials for stable operation in lithium-ion batteries (e.g., through a comprehensive design of material structure and chemical composition). The investigation of composition-dependent morphology evolution in the delithiated Li-SiGe ternary alloy also significantly broadens our understanding of dealloying in complex systems, and it is complementary to the well-established understanding of dealloying behavior in binary systems (e.g., Au-Ag alloys).

Transition metal oxides have attracted great interest as alternative anode materials for rechargeable lithium-ion batteries. Among them, ruthenium dioxide is considered to be a prototype material that reacts with the Li ions in the conversion type. In situ transmission electron microscopy reveals a two-step process during the initial lithiation of the RuO2 nanowire anode at atomic resolution. The first step is characterized by the formation of the intermediate phase LixRuO2 due to the Li-ion intercalation. The following step is manifested by the solid-state amorphization reaction driven by advancing the reaction front. The crystalline/amorphous interface is consisted of {011} atomic terraces, revealing the orientation-dependent mobility. In the crystalline matrix, lattice disturbance and dislocation are identified to be two major stress-induced distortions. The latter can be effective diffusion channels, facilitating transportation of the Li ions inside the bulk RuO2 crystal and further resulting in non-uniform Li-ion distribution. It is expected that the local enrichment of the Li ions may account for the homogeneous nucleation of dislocations in the bulk RuO2 crystal and the special island-like structures. These results elucidate the structural evolution and the phase transformation during electrochemical cycling, which sheds light on engineering RuO2 anode materials.

Voltage and capacity fading of layer structured lithium and manganese rich (LMR) transition metal oxide is directly related to the structural and composition evolution of the material during the cycling of the battery. However, understanding such evolution at atomic level remains elusive. On the basis of atomic level structural imaging, elemental mapping of the pristine and cycled samples, and density functional theory calculations, it is found that accompanying the hoping of Li ions is the simultaneous migration of Ni ions toward the surface from the bulk lattice, leading to the gradual depletion of Ni in the bulk lattice and thickening of a Ni enriched surface reconstruction layer (SRL). Furthermore, Ni and Mn also exhibit concentration partitions within the thin layer of SRL in the cycled samples where Ni is almost depleted at the very surface of the SRL, indicating the preferential dissolution of Ni ions in the electrolyte. Accompanying the elemental composition evolution, significant structural evolution is also observed and identified as a sequential phase transition of C2/m → I41 → Spinel. For the first time, it is found that the surface facet terminated with pure cation/anion is more stable than that with a mixture of cation and anion. These findings firmly established how the elemental species in the lattice of LMR cathode transfer from the bulk lattice to surface layer and further into the electrolyte, clarifying the long-standing confusion and debate on the structure and chemistry of the surface layer and their correlation with the voltage fading and capacity decaying of LMR cathode. Therefore, this work provides critical insights for design of cathode materials with both high capacity and voltage stability during cycling.

Nanoscale finger-like structures are fabricated by pulling bulk silver wires at room temperature using a pair of cutter pliers. The diameter of these nanofingers (NFs) is found to have a narrow distribution ( d = 15 ± 3 nm) and high uniformity along the length, which relies on the strain hardening induced by dislocation starvation. Theoretical prediction of the length agrees well with the experimental observation.

Tin oxide (SnO2) is widely recognized as a promising negative electrode material for high capacity lithium (Li)-ion batteries due to its high-energy density. Recent experiments1–3 using high-resolution Transmission Electron Microscopy (TEM) show that the lithiation process in SnO2 nanowires occurs in two stages. Initially, rapid Li diffusion occurs from one end of the nanowire to the other through narrow stripes along the electrode. This stage is followed by a second stage where Li diffuses through the bulk at a much lower speed throughout the electrode leading to amorphization. In order to understand this complex phenomenon we have employed a finite element (FE) modeling in conjunction with previous in-situ TEM experiments3 to study the lithiation of SnO2 nanoelectrodes. In the experimental work, SnO2 nanowire lithiation process was characterized using in-situ TEM where the SnO2 nanowire was placed on the negative side of the in-situ setup and was brought in direct contact with the Li source.1 The idea behind FE in this context is to formulate the lithiation process using physical models which provide results consistent with experimental observations. The model is based on the understanding that in SnO2 nanowire a slip plane is created due to non-perfect contact of the source or defects and the stress at the slip planes leads to significantly higher diffusion coefficient.1 The developed constitutive model which has been implemented in FE, captures the formation of striped diffusion regime and corresponding electrode’s expansion during the lithiation of SnO2. In particular, the model incorporates the formation of stripes by using a variable nonlinear diffusivity coefficient which is a function of the concentration-dependent stress. The structural changes associated with the Li diffusion/intercalation in the electrode geometry are modeled using a 2D plane strain assumption and linear elastic material. The results from the model show a clear formation of striped diffusion regime due to the induced stresses, at low concentrations of Li. This results in a small strain of 10% within the nanowire and is followed by a bulk diffusion and expansion at higher concentrations. Thus, the simulations allow for the spatiotemporally resolved prediction and analysis of Li diffusion/intercalation and its influence on the electrode performance under the realistic operation conditions. References 1. A. Nie, L. Y. Gan, Y. Cheng, H. Asayesh-Ardakani, Q. Li, C. Dong, R. Tao, F. Mashayek, H. T. Wang, U. Schwingenschlgl, R. F. Klie, and R. S. Yassar, ACS Nano, 7, 6203–6211 (2013). 2. L. Q. Zhang, X. H. Liu, Y. C. Perng, J. Cho, J. P. Chang, S. X. Mao, Z. Z. Ye, and J. Y. Huang, Micron, 43, 1127–1133 (2012). 3. J. Y. Huang, L. Zhong, C. M. Wang, J. P. Sullivan, W. Xu, L. Q. Zhang, S. X. Mao, N. S. Hudak, X. H. Liu, A. Subramanian, H. Fan, L. Qi, A. Kushima, and J. Li, 330, 1515 LP – 1520 (2010).

The development of sodium-ion batteries has drawn lots of attention recently due to the low-cost and eco-friendly sodium source. However, a fundamental understanding of the sodiation behavior for commonly used electrode materials is still limited. Here, combining in situ transmission electron microscopy, aberration-corrected scanning transmission electron microscopy, and ex situ battery cycling tests, the lithiation and sodiation behavior of ZnO nanowires is investigated. The findings show a direct correlation between the mechanical behavior of the lithiated/sodiated ZnO nanowires and their electrochemical cyclability. The mechanical brittleness of LiZn and the formation of nanocracks lead to the poor cyclability of Li-ion batteries with a ZnO anode. However, the sodiated ZnO nanowires show profuse dislocation plasticity. The observed high-density dislocations offer the sodiated ZnO anode more ductility and subsequently better cyclability than its Li-ion counterpart. The results reveal the importance of understanding the correlation between mechanical properties of battery electrodes and their cycling abilities.

Identifying different phases of VO2 during the metal−insulator phase transition is critical for device application due to the difference of electrical, mechanical and magnetic properties of phases. However, most studies so far were carried out using microprobe analyses, which lack the spatial resolution needed to identify nanoscale phases and changes. Taking advantage of in situ low temperature aberration-corrected scanning transmission electron microscopy, we observed the existence of M2 phase alongside M1 and R phase in the W-doped nanowires close to transition temperature. The localized stress caused by adding W in the structure results in the stabilization of nanosize grains of M2 phase in structure along with M1 and R phases. The observation of the metastable M2 phase even for unclamped nanowires suggests the possibility of finely modulating the phase diagram of VO2 through a combination of finite size and doping.

For the first time, a fast heating–cooling process is reported for the synthesis of carbon-coated nickel (Ni) nanoparticles on a reduced graphene oxide (RGO) matrix (nano-Ni@C/RGO) as a high-performance H2O2 fuel catalyst. The Joule heating temperature can reach up to ≈2400 K and the heating time can be less than 0.1 s. Ni microparticles with an average diameter of 2 µm can be directly converted into nanoparticles with an average diameter of 75 nm. The Ni nanoparticles embedded in RGO are evaluated for electro-oxidation performance as a H2O2 fuel in a direct peroxide–peroxide fuel cell, which exhibits an electro-oxidation current density of 602 mA cm−2 at 0.2 V (vs Ag/AgCl), ≈150 times higher than the original Ni microparticles embedded in the RGO matrix (micro-Ni/RGO). The high-temperature, fast Joule heating process also leads to a 4–5 nm conformal carbon coating on the surface of the Ni nanoparticles, which anchors them to the RGO nanosheets and leads to an excellent catalytic stability. The newly developed nano-Ni@C/RGO composites by Joule heating hold great promise for a range of emerging energy applications, including the advanced anode materials of fuel cells.

In situ straining in nanocrystalline Au thin films reveals a new fracture mechanism, i.e. crack propagation by atomic migration. The crack propagates by repetitively nucleating and moving atomic steps from the tip region to the crack rear. The stress concentration at the tip helps in the step nucleation process. The elastic energy density at the notch root decreases with increasing notch angle, which implies cracks with small angles can propagate along grain boundaries more easily.

Nanocrystalline Au films were in situ strained in a high resolution transmission electron microscope, which demonstrated that the diffusion-assisted intergranular fracture was the dominant failure mode. Grain orientation with respect to grain boundaries (GBs) imposes important effect on the crack propagation and blunting. The low surface energy and high diffusion mobility of {111} planes lead to a notch-like crack. The stress concentration at the tip may help breaking {111} planes layer by layer and thus advance the crack. Cracks can be diverted from the preset path by GBs and grow into the grain interior, which has never been revealed by other experiments and molecular dynamics simulations.

In rechargeable lithium-ion batteries, understanding the atomic-scale mechanism of Li-induced structural evolution occurring at the host electrode materials provides essential knowledge for design of new high performance electrodes. Here, we report a new crystalline-crystalline phase transition mechanism in single-crystal Zn-Sb intermetallic nanowires upon lithiation. Using in situ transmission electron microscopy, we observed that stacks of atomic planes in an intermediate hexagonal (h-)LiZnSb phase are "shuffled" to accommodate the geometrical confinement stress arising from lamellar nanodomains intercalated by lithium ions. Such atomic rearrangement arises from the anisotropic lithium diffusion and is accompanied by appearance of partial dislocations. This transient structure mediates further phase transition from h-LiZnSb to cubic (c-)Li2ZnSb, which is associated with a nearly "zero-strain" coherent interface viewed along the [001]h/[111]c directions. This study provides new mechanistic insights into complex electrochemically driven crystalline-crystalline phase transitions in lithium-ion battery electrodes and represents a noble example of atomic-level structural and interfacial rearrangements.