Semiconductor nanostructures have attracted much attention as promising candidates for future electro-optical devices. In nanostructures, the carrier-state density is concentrated in discrete energy levels, which enables the enhancement of exciton oscillator strength and light-emitting efficiency. As a result, the performance of nanostructure-based optical devices is expected to be improved and be less temperature dependent.[1]Among the wide variety of semiconductor nanostructures, ZnO nanostructures, as wide bandgap semiconductors, are even more attractive for high-efficiency short-wavelength optoelectronic nanodevices, [2±4] due to their large excitonic binding energy (»60 meV) and high mechanical and thermal stabilities. For one-dimensional ZnO nanostructures, different shape structures, such as tetrapod nanorods, [5,6] nanowires, [7,8]

We report on a novel MoS2/S-doped g-C3N4 heterojunction film with high visible-light photoelectrochemical (PEC) performance. The heterojunction films are prepared by CVD growth of S-doped g-C3N4 film on indium-tin oxide (ITO) glass substrates, with subsequent deposition of a low bandgap, 1.69 eV, visible-light response MoS2 layer by hydrothermal synthesis. Adding thiourea into melamine as the coprecursor not only facilitates the growth of g-C3N4 films but also introduces S dopants into the films, which significantly improves the PEC performance. The fabricated MoS2/S-doped g-C3N4 heterojunction film offers an enhanced anodic photocurrent of as high as ∼1.2 × 10(-4) A/cm(2) at an applied potential of +0.5 V vs Ag/AgCl under the visible light irradiation. The enhanced PEC performance of MoS2/S-doped g-C3N4 film is believed due to the improved light absorption and the efficient charge separation of the photogenerated charge at the MoS2/S-doped g-C3N4 interface. The convenient preparation of carbon nitride based heterojunction films in this work can be widely used to design new heterojunction photoelectrodes or photocatalysts with high performance for H2 evolution.

electric vehicles. [1] The next-generation LIBs must meet a multitude of stringent requirements, including excellent cycle stability, high capacity, high energy and power densities, high safety, and low cost. [2] As an alternative to the graphite anode for commercial LIBs, Si has attracted considerable attention, due to its high theoretical capacity of 3579 mA h g −1 , low operating potential, abundance, and low cost. However, the practical applications of Si-based anode materials are hindered by low Li + diffusivity and electrical conductivity and especially by drastic volume changes (≈300%) during lithiation/delithiation. The latter problem can cause Si pulverization, loss of electrical contact, and consumption of active Li associated with the unstable evolution of solid electrolyte interphases (SEIs). As a result, Si-based anodes generally exhibit low Coulombic efficiency, poor cycle stability, and rate capability. [3] To address these problems, one effective approach is to use Si nanoparticles (NPs) for the facile accommodation of large volume changes. But the high specific surface area associated with nanomaterials causes aggregation of Si NPs during cycling and provides plenty of active surface sites to form SEIs. Moreover, repeated expansion and contraction of Si NPs induce fracture and uncontrolled formation of Si/C composites represent one promising class of anode materials for next-generation lithium-ion batteries. To achieve high performances ofSi-based anodes, it is critical to control the surface oxide of Si particles, so as to harness the chemomechanical confinement effect of surface oxide on the large volume changes of Si particles during lithiation/delithiation. Here a systematic study of Si@SiO x /C nanocomposite electrodes consisting of Si nanoparticles covered by a thin layer of surface oxide with a tunable thickness in the range of 1-10 nm is reported. It is shown that the oxidation temperature and time not only control the thickness of the surface oxide, but also change the structure and valence state of Si in the surface oxide. These factors can have a strong influence on the lithiation/delithiation behavior of Si nanoparticles, leading to different electrochemical performances. By combining experimental and modeling studies, an optimal thickness of about 5 nm for the surface oxide layer of Si nanoparticles is identified, which enables a combination of high capacity and long cycle stability of the Si@SiO x /C nanocomposite anodes. This work provides an in-depth understanding of the effects of surface oxide on the Si/C nanocomposite electrodes. Insights gained are important for the design of high-performance Si/C composite electrodes.

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