nanogenerator can only output alternating current and the output current density is quite small (0.01-0.1 A m −2 ), [5] which limits its widespread applications. [6] Recently, the vertical movement between the metal and semiconducting polymer has been demonstrated to output intermittent current peaks with low current density (2.7-62.4 µA cm −2 ), [7] where the metal contacts with polymer periodically. On the other hand, the microscale direct current generator based on sliding between metal tip and semiconductor has been demonstrated, [8] where the mechanism was ascribed to the triboelectric effect. However, the mechanism of triboelectric effect is confusing, [9] as the fundamental physical mechanism of the charge transfer process during friction is not solved. [6,10] Herein, we have demonstrated a macroscale direct-current generator through a moving van der Waals Schottky diode by dynamically moving graphene or metal film over Si or GaAs substrates. The mechanism of the moving Schottky diode generator is based on the built-in electric field separation of the diffusing carriers emitted by the appearance and disappearance of the depletion layer in moving Schottky diode. The working lifetime and flexibility can be properly improved by choosing graphene as the metal material, which is outstanding not only because of its high conductive but also the high mechanical physical properties. [11,12] Actually, static graphene/semiconductor van der Waals heterostructure-based solar cells, [13] self-driven photodetectors, [14] and water flow nanogenerator [15] have been proposed. Compared with metal, graphene film has the unique advantage of high flexibility and durability, which promises the graphene film/ silicon moving Schottky diode generator working well after 10 000 runs back and forth. The persistent direct-current generating ability firmly demonstrates that the physical mechanism of the moving Schottky diode generator is not caused by the triboelectricity. Instead, we uniquely propose that the dynamic disappearance and establishment of Schottky junction during the movement between graphene/metal and semiconductors is the origin of the direct current output. The proposed mechanism is self-consistent and can well explain the systematic experiments presented herein. This moving Schottky diode direct-current generator can light up a blue light-emitting diode (LED) and a flexible graphene wristband is demonstrated for the first time. Under the guidance of the mechanism, we achieved a currentdensity output up of ≈40 A m −2 through minimizing the contact Traditionally, Schottky diodes are used statically in the electronic information industry while dynamic or moving Schottky diode-based applications are rarely explored. Herein, a novel Schottky diode named "moving Schottky diode generator" is designed, which can convert mechanical energy into electrical energy by means of lateral movement between the graphene/metal film and semiconductor. The mechanism is based on the built-in electric field separation of the diffusing carr...

Recently, several reports have demonstrated that a moving droplet of seawater or ionic solution over monolayer graphene produces an electric power of about 19 nW, and this has been suggested to be a result of the pseudocapacitive effect between graphene and the liquid droplet. Here, we show that the change in the triboelectrification-induced pseudocapacitance between the water droplet and monolayer graphene on polytetrafluoroethylene (PTFE) results in a large power output of about 1.9 μW, which is about 100 times larger than that presented in previous research. During the graphene transfer process, a very strong negative triboelectric potential is generated on the surface of the PTFE. Positive and negative charge accumulation, respectively, occurs on the bottom and the top surfaces of graphene due to the triboelectric potential, and the negative charges that accumulate on the top surface of graphene are driven forward by the moving droplet, charging and discharging at the front and rear of the droplet.

Tailoring molybdenum selenide electrocatalysts with tunable phase and morphology is of great importance for advancement of hydrogen evolution reaction (HER). In this work, phase- and morphology-modulated N-doped MoSe /TiC-C shell/core arrays through a facile hydrothermal and postannealing treatment strategy are reported. Highly conductive TiC-C nanorod arrays serve as the backbone for MoSe nanosheets to form high-quality MoSe /TiC-C shell/core arrays. Impressively, continuous phase modulation of MoSe is realized on the MoSe /TiC-C arrays. Except for the pure 1T-MoSe and 2H-MoSe , mixed (1T-2H)-MoSe nanosheets are achieved in the N-MoSe by N doping and demonstrated by spherical aberration electron microscope. Plausible mechanism of phase transformation and different doping sites of N atom are proposed via theoretical calculation. The much smaller energy barrier, longer HSe bond length, and diminished bandgap endow N-MoSe /TiC-C arrays with substantially superior HER performance compared to 1T and 2H phase counterparts. Impressively, the designed N-MoSe /TiC-C arrays exhibit a low overpotential of 137 mV at a large current density of 100 mA cm , and a small Tafel slope of 32 mV dec . Our results pave the way to unravel the enhancement mechanism of HER on 2D transition metal dichalcogenides by N doping.

As ynergistic Nd oping plus PO 4 3À intercalation strategy is used to induce high conversion (ca. 41 %) of 2H-MoS 2 into 1T-MoS 2 ,which is muchhigher than single Ndoping (ca. 28 %) or single PO 4 3À intercalation (ca. 10 %). Ascattering mechanism is proposed to illustrate the synergistic phase transformation from the 2H to the 1T phase,w hich was confirmed by synchrotron radiation and spherical aberration TEM. To further enhance reaction kinetics,t he designed (N,PO 4 3À )-MoS 2 nanosheets are combined with conductive vertical graphene (VG) skeleton forming binder-free arrays for high-efficiency hydrogen evolution reaction (HER). Owing to the decreased band gap,l ower d-band center,a nd smaller hydrogen adsorption/desorption energy,t he designed (N,PO 4 3À )-MoS 2 /VGe lectrode shows excellent HER performance with al ower Tafel slope and overpotential than N-MoS 2 /VG, PO 4 3À -MoS 2 /VGc ounterparts,a nd other Mo-base catalysts in the literature.

Two-dimensional (2D) atomic crystals, especially graphene, have received much attention. However, the main shortcoming of graphene is its zero band gap. Silicon carbide, composed of silicon and carbon, is a typical wurtzite compound semiconductor, with more than 250 alloy types. Herein, we give some evidence of the solution exfoliation of 2D SiC nanoflakes with thickness down to 0.5–1.5 nm. Transmission electron microscopy (TEM) and X-ray diffraction characterizations reveal that graphitic (0001)/(0001̅) SiC most possibly has been formed by sonication of wurtzite SiC. Graphene, which is also produced in this process, naturally forms the ultrathin substrate facilitating the TEM characterization of 2D SiC. The mechanism of this exfoliation process should be related to the surface reconstruction of wurtzite SiC into graphitic SiC. Photoluminescence spectra show a strong light-emitting ability and a quantum-confinement-induced emission peak at 373 nm for these ultrathin SiC nanosheets.

Ru x Ti 1Àx Nb 2 O 7 (x ¼ 0 and 0.01) materials have been synthesized via a solid-state reaction method. X-ray diffraction combined with Rietveld refinements demonstrates that both samples have a Wadsley-Roth shear structure with a C2/m space group without any impurities, and that the unit cell volume increases after the trace Ru 4+ doping. Scanning electron microscopy and specific surface area tests reveal that the Ru 4+ doping decreases the average particle size. The Li + ion diffusion coefficient and electronic conductivity of Ru 0.01 Ti 0.99 Nb 2 O 7 are respectively 64% and at least two orders of magnitude larger than those of the pristine TiNb 2 O 7 . First-principles calculations show that the increased electronic conductivity can result from the formation of impurity bands after the Ru 4+ doping. Ru 0.01 Ti 0.99 Nb 2 O 7 exhibits a large initial discharge capacity of 351 mA h g À1 at 0.1 C between 3.0 and 0.8 V vs. Li/Li + , approaching its theoretical capacity (388 mA h g À1 ). At 5 C, unlike the pristine TiNb 2 O 7 with a small charge capacity of 115 mA h g À1 , Ru 0.01 Ti 0.99 Nb 2 O 7 delivers a large value of 181 mA h g À1 , even exceeding the theoretical capacity of the popular spinel Li 4 Ti 5 O 12 (175 mA h g À1 ). After 100 cycles, Ru 0.01 Ti 0.99 Nb 2 O 7 shows a large capacity retention of 90.1%. These outstanding electrochemical performances can be attributed to its improved Li + ionic and electronic conductivity as well as smaller particle size. Electronic supplementary information (ESI) available: Crystal structure of TiNb 2 O 7 showing the m  n  N (m ¼ n ¼ 3) ReO 3 -type blocks (Fig. S1); Nyquist plots of the Li 4 Ti 5 O 12 /Li cell and Li + ion diffusion coefficient of Li 4 Ti 5 O 12 (Fig. S2); Coulombic efficiency of the Ru 0.01 Ti 0.99 Nb 2 O 7 /Li cell at 5 C (Fig. S3); ex situ XRD patterns of TiNb 2 O 7 electrodes (Fig. S4); SEM image and EDX mapping of Ru 0.01 Ti 0.99 Nb 2 O 7 (Fig. S5). See

2D materials hold great potential for designing novel electronic and optoelectronic devices. However, 2D material can only absorb limited incident light. As a representative 2D semiconductor, monolayer MoS can only absorb up to 10% of the incident light in the visible, which is not sufficient to achieve a high optical-to-electrical conversion efficiency. To overcome this shortcoming, a "gap-mode" plasmon-enhanced monolayer MoS fluorescent emitter and photodetector is designed by squeezing the light-field into Ag shell-isolated nanoparticles-Au film gap, where the confined electromagnetic field can interact with monolayer MoS . With this gap-mode plasmon-enhanced configuration, a 110-fold enhancement of photoluminescence intensity is achieved, exceeding values reached by other plasmon-enhanced MoS fluorescent emitters. In addition, a gap-mode plasmon-enhanced monolayer MoS photodetector with an 880% enhancement in photocurrent and a responsivity of 287.5 A W is demonstrated, exceeding previously reported plasmon-enhanced monolayer MoS photodetectors.

TiNbO is explored as a new anode material for lithium-ion batteries. Microsized TiNbO particles (M-TiNbO) are fabricated through a simple solid-state reaction method and porous TiNbO microspheres (P-TiNbO) are synthesized through a facile solvothermal method for the first time. TiNbO exhibits a Wadsley-Roth shear structure with a structural unit composed of a 3 × 4 octahedron-block and a 0.5 tetrahedron at the block-corner. P-TiNbO with an average sphere size of ∼2 μm is constructed by nanoparticles with an average size of ∼100 nm, forming inter-particle pores with a size of ∼8 nm and inter-sphere pores with a size of ∼55 nm. Such desirable porous microspheres are an ideal architecture for enhancing the electrochemical performances by shortening the transport distance of electrons/Li-ions and increasing the reaction area. Consequently, P-TiNbO presents outstanding electrochemical performances in terms of specific capacity, rate capability and cyclic stability. The reversible capacities of P-TiNbO are, respectively, as large as 296, 277, 261, 245, 222, 202 and 181 mA h g at 0.1, 0.5, 1, 2, 5, 10 and 20 C, which are obviously larger than those of M-TiNbO (258, 226, 210, 191, 166, 147 and 121 mA h g). At 10 C, the capacity of P-TiNbO still remains at 183 mA h g over 500 cycles with a decay of only 0.02% per cycle, whereas the corresponding values of M-TiNbO are 119 mA h g and 0.04%. These impressive results indicate that P-TiNbO can be a promising anode material for lithium-ion batteries of electric vehicles.