Nitrogen-doped graphene-supported zinc sulfide nanorods as efficient Pt-free for visible-light photocatalytic hydrogen production

Nitrogen-doped graphene-ZnS composite (NG-ZnS) was synthesized by thermal treatment of graphene-ZnS composite (G-ZnS) in NH₃ medium. In the second step, the as-synthesized samples were deposited on indium tin oxide glass (ITO) by electrophoretic deposition for photocatalytic hydrogen evolution reaction. The as-prepared NG-ZnS-modified ITO electrode displayed excellent photocatalytic activity, rapid transient photocurrent response, superior stability and high recyclability compared to the pure ZnS and G-ZnS-modified ITO electrode due to the synergy between the photocatalytic activity of ZnS nanorods and the large surface area and high conductivity of N-graphene.     

Facile synthesis of carbon self-doped g-C3N4 for enhanced photocatalytic hydrogen evolution

Graphite carbon nitride (g-C₃N₄) is an appealing metal-free photocatalyst for hydrogen evolution, but the potential has been limited by its poor visible-light absorption and unsatisfactory separation of photo-induced carriers. Herein, a facile one-pot strategy to fabricate carbon self-doped g-C₃N₄ composite through the calcination of dicyanamide and trace amounts of dimethylformamide is presented. The as-obtained carbon self-doped catalyst is investigated by X-ray photoelectron spectroscopy (XPS), confirming the substitution of carbon atoms in original sites of bridging nitrogen. We demonstrate that the as-prepared materials display remarkably improved visible-light absorption and optimized electronic structure under the premise of principally maintaining the tri-s-triazine based crystal framework and surface properties. Furthermore, the carbon doped g-C₃N₄ composite simultaneously weakens the transportation barrier of charge carriers, suppresses charge recombination and raises the separated efficiency of photoinduced holes and electrons on account of the extension of pi conjugated system. As a result, carbon self-doped g-C₃N₄ exhibits 4.3 times greater photocurrent density and 5.2 times higher hydrogen evolution rate compared with its bulk counterpart under visible light irradiation.     

Influence of design and operating conditions on the performance of tandem photoelectrochemical reactors

Solar-driven photoelectrochemical water splitting technology is a promising avenue for a sustainable hydrogen production. In this work, a comprehensive 2-dimensional model is developed and numerically simulated with hematite (α-Fe₂O₃) as the principal photoelectrode. The model evaluates light absorption, charge transport and electrochemical reactions to elucidate the effects of light transmitting materials, electrolyte height and electrolyte velocity on hydrogen and oxygen gas production. Results indicated that major losses in photocurrents are attributed to the transparent conducting oxide while losses due to the electrolyte increase with its height. Gas concentrations increase with increasing photocurrent densities and also in the direction of the flow. Gas bubbles however decrease with increasing electrolyte velocity. From these results, light reception in the reactor is uneven and poses a bigger challenge due to the bias in gas bubble distribution. Prospects of upscaling tandem schemes hence not only lie in the semiconductor material combinations but rather in the proper integration of system components and operating conditions.     

应力状态对J55油管钢钝化膜电性能的影响

油管钢在土壤环境中受到腐蚀后会在表面形成一层保护基体减缓腐蚀的钝化膜。本文讲述了采用电化学阻抗谱(EIS)和光电流技术研究J55油管钢在模拟土壤环境(高pH值)中,拉伸、压缩及弯曲应力状态下所形成钝化膜的电化学性能,以期为碳钢腐蚀与防护提供一定的理论参考。     

Multifunctional π-conjugated poly (3-methylthiophene) nanotubes for optoelectronic and field emissive devices

Multifunctional properties of nanomaterials becomes a hot topic in nano research for the development of multifunctional devices, because modern devices need multifunctional platform for the high efficient plural performance on a single device. Here, we introduce a multifunctional π-conjugated poly (3-methylthiophene) (P3MT) nanotube (NT), showing controllable optical and electrical properties through the control of doping level. P3MT NTs were electrochemically synthesized in the low temperature (−40 °C) on the nanoporous template. The change of doping level by post cyclic voltammetry (CV) treatment on the P3MT lead the variance of polaron/bipolaron band, resulting into the drastic change of ultraviolet-visible absorption and photoluminescence properties. While P3MT NTs before CV treatment show an ohmic behavior in the current-voltage characteristics, those after CV treatment show high photocurrent. From the field emission experiment, the P3MT NTs before CV treatment have a relatively low turn-on electric field and stable electron emission property compared to the P3MT NTs after CV treatment. This shows that the π-conjugated polymers should be shed new light on their multifunctionality for the potential application to the multifunctional platform of opto-electronic nanodevices.     

Enhanced electrical and photocurrent characteristics of sol-gel derived Ni-doped PbTiO3 thin films

Partial substitution of group 10 metal for titanium is predicted theoretically to be one of the most effective ways to decrease the band gap of PbTiO₃-based ferroelectric photovoltaic materials. It is therefore of interest to experimentally investigate their ferroelectric and photovoltaic properties. In this work, we focus on the electrical and photocurrent properties of Ni-doped PbTiO₃ thin films prepared via a sol-gel route. The nickel incorporation does not modify the crystalline structure of PbTiO₃ thin film, but it can increase the dielectric constant, ferroelectric polarization and photocurrent, and simultaneously decrease the band gap. The maximum remnant polarization (P_r) of 58.1 μC/cm² is observed in PbTi_0.8Ni_0.2O₃ thin film, and its photocurrent density is improved to be approximately one order larger than that of PbTiO₃ thin film and simultaneously exhibits the polarization-dependent switching characteristic, which may be a promising choice for ferroelectric photovoltaic applications.     

Highly efficient hematite films via mid-/ex-situ Sn-doping for photoelectrochemical water oxidation

In this study, we report the facile fabrication of Sn-doped hematite film via mid-situ and ex-situ doping methods for efficient photoelectrochemical (PEC) performances. The morphology of Sn-doped Fe₂O₃ films was varied with Sn precursor in the mid-situ doping process. The addition of SnCl₂ rendered a smooth-surfaced and well-distributed nanorod morphology, but SnCl₄ gave a deformed nanorod structure covered with layered coalescence of SnO₂ particles. The former demonstrated much higher photoelectrochemical performances as photoanodes than the latter. The photocurrent can be further improved by surface modification with SnCl₄ through spin-coating method. The effects of Sn precursors on the morphology, surface characteristics and the PEC properties of the photoanodes are investigated.     

Electrical and photoelectrochemical characteristics of flexible CdS nanocomposite/conducting polymer heterojunction

The electrical properties of CdS-polyvinyl alcohol (CdS-PVA) nanocomposites have been investigated in details. The junction behavior of CdS-PVA and a conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) heterojunction have been studied. The current–voltage characteristics of the nanocomposite samples have also performed at different bending angles. The bending study has been carried out after deposition of CdS-PVA and CdS-PVA/PEDOT:PSS heterojunction films on indium tin oxide coated (ITO) flexible polyethylene terephthalate (PET) substrates. Spectral dependent photoconductive properties of the nanocomposite-polymer heterojunctions have been investigated. The electrochemical photosensing behaviors have been demonstrated using CdS-PVA nanocomposites and CdS-PVA/PEDOT:PSS heterojunction films as photoanodes.     

Enhanced visible light photocurrent generation at surface-modified TiO2 nanotubes

Photoelectrodes consisting of TiO₂ nanotube layers with different thicknesses (0.5 μm, 1.7 μm, 3 μm, 6 μm, 9 μm, and 18 μm) were prepared by anodization of titanium substrates and subsequent surface modification by a heat treatment at 400 °C in the presence of urea pyrolysis products. In contrast to unmodified TiO₂ nanotubes, the modified photoelectrodes exhibit photocurrents under visible light irradiation down to 750 nm. Photocurrent transients indicate enhanced recombination unless a suitable hole-scavenger, like iodide, is present since the photogenerated holes do not oxidize water efficiently. In the visible light the photoconversion efficiency increases significantly with nanotube length. The maximum incident photon-to-current efficiency (IPCE) was observed for tubes with the length of 6-9 μm (IPCE ∼4.5% and 1.4% at 450 nm and 550 nm, respectively) and the photocurrent enhancement with increasing tube length is found to be stronger at longer irradiations wavelengths.