High-Throughput Multi-Plume Pulsed-Laser Deposition for Materials Exploration and Optimization

A high-throughput multi-plume pulsed-laser deposition(MPPLD) system has been demonstrated and compared to previous techniques. Whereas most com binatorial pulsedlaser deposition(PLD) systems have focused on achieving thickness uniformity using sequential multilayer deposition and masking followed by post-deposition annealing, MPPLD directly deposits a compositionally varied library of compounds using the directionality of PLD plumes and the resulting spatial variations of deposition rate. This system is more suitable for high-throughput compound thin-fllm fabrication.

功能可切换的金属/半导体结实现水氧化产物可控选择的高效光催化全分解水

本文设计了一种Cu纳米颗粒(NPs)修饰TiO2空心球壳的新型光催化剂(Cu/TiO2),这种金属/半导体光催化剂在紫外光和可见光下均能实现高效光催化全分解水.在报道过的TiO2基光催化剂中,Cu/TiO2的可见光全分解水活性处于最高水平.有趣的是,Cu和TiO2形成的金属/半导体结可以通过调节入射光波长(紫外光或可见光)来控制改变光催化分解水反应路径,进而实现对水氧化产物(H2O2或O2)的选择.在紫外光照射下,TiO2上的光生电子在Cu/TiO2肖特基结的作用下被Cu NPs捕获,并参与水还原反应产生H2,留在TiO2上的光生空穴通过两电子过程参与水氧化反应产生H2O2;在可见光下,Cu NPs的局域表面等离子共振(LSPR)效应发挥作用,产生热电子并将其注入至TiO2中,参与水还原反应产生H2,Cu NPs产生的热空穴通过四电子过程参与水氧化反应产生O2.这种功能可切换的金属/半导体结的设计可以对研究和理解光催化全分解水反应机理提供帮助.

Black TiO_(2) for solar hydrogen conversion

Titanium dioxide(TiO_(2))has been widely investigated for photocatalytic H_(2) evolution and photoelectrochemical(PEC)water splitting since 1972.However,its wide bandgap(3.0-3.2 eV)limits the optical absorption of TiO_(2) for sufficient utilization of solar energy.Blackening TiO_(2) has been proposed as an effective strategy to enhance its solar absorption and thus the photocatalytic and PEC activities,and aroused widespread research interest.In this article,we reviewed the recent progress of black TiO_(2) for photocatalytic H_(2) evolution and PEC water splitting,along with detailed introduction to its unique structural features,optical property,charge carrier transfer property and related theoretical calculations.As summarized in this review article,black TiO_(2) could be a promising candidate for photoelectrocatalytic hydrogen generation via water splitting,and continuous efforts are deserved for improving its solar hydrogen efficiency.

A general and simple method for evaluating the electrical transport performance of graphene by the van der Pauw–Hall measurement

Expected for many promising applications in the field of electronics and optoelectronics, a reliable method for the characterization of graphene electrical transport properties is desired to predict its device performance or provide feedback for its synthesis.However, the commonly used methods of extracting carrier mobility from graphene field effect transistor or Hall-bar is time consuming, expensive, and significantly affected by the device fabrication process other than graphene itself.Here we reported a general and simple method to evaluate the electrical transport performance of graphene by the van der Pauw–Hall measurement.By annealing graphene in vacuum to remove the adsorbed dopants and then exposing it in ambient surroundings, carrier mobility as a function of density can be measured with the increase of carrier density due to the dopant re-adsorption from the surroundings.Further, the relationship between the carrier mobility and density can be simply fitted with a power equation to the first level approximation, with which any pair of measured carrier mobility and density can be normalized to an arbitrary carrier density for comparison.We experimentally demonstrated the reliability of the method, which is much simpler than making devices and may promote the standard making for graphene characterization.

Criteria for the growth of large-area adlayer-free monolayer graphene films by chemical vapor deposition

Homogeneity is important to material applications for good performance of individual devices,for making AB-stacked bilayer graphene in a layer-by-layer stacking order,and from the point of view of industrial production.Among many properties to be controlled,for the case of graphene,the thickness(or layer number)uniformity is the prerequisite.Chemical vapor deposition(CVD)of C precursors on Cu substrates is the most popular method to produce large-area graphene films.To date,precise control on the number of graphene layers as well as the uniformity over a large area is still very challenging.In this work,with a further understanding of the factors affecting adlayer growth,the synthesis of large-area adlayer-free monolayer graphene(MLG)films was achieved up to tens of squared centimeters in area by just using untreated Cu foil and a normal CVD process.We found that keeping equal C precursor concentration on the two sides of the Cu substrate is a criterion in addition to other factors such as the ratio of H:C and the substrate surface morphology for the growth of adlayer-free MLG.This finding is not only of great significance for the industrial production of large-area adlayer-free MLG films but also instructive for the synthesis of homogeneous few-layer graphene.

Morphology-dependent electrocatalytic performance of Fe_(2)(MoO_(4))_(3) for electro-oxidation of methanol in alkaline medium

Electrochemically synthesized nanosphere,nanorod and nanotube Fe_(2)(MoO_(4))_(3) at optimized temperature and current density are characterized with XRD,SEM,TEM,XPS.Crystal lattices of the three types Fe_(2)(MoO_(4))_(3) detected by HRTEM are well matched with the simulation analysis results from Materials Studio 6.0 based on the inorganic crystal structure database(ICSD)data and the modified XRD lattice parameters.The ratios of Fe/Mo on the surface resulted from XPS analysis are 1.47,1.63 and 2.22 respectively for nanosphere,nanorod and nanotube.The mixture of Fe_(2)(MoO_(4))_(3) with polytetrafluoroethylene dispersion are coated on glass carbon substrate as electrode for electrocatalytic performance test by cyclic voltammetries in 0.1 mol/L KOH and 1 mol/L methanol electrolyte.Methanol oxidation peak current density of the Nanotube-Fe_(2)(MoO_(4))_(3)/GCEs electrode is 3.27 mA/cm^(2) higher than 2.8 mA/cm^(2) of platinum foil electrode,which shows enhanced catalytic activity of Nanotube-Fe_(2)(MoO_(4))_(3)/GCEs.The cyclic stability in terms of peak current retention are 91%,92%and 88%respectively for Nanosphere-Fe_(2)(MoO_(4))_(3)/GCE,Nanorod-Fe_(2)(MoO_(4))_(3)/GCE and Nanotube-Fe_(2)(MoO_(4))_(3)/GCE electrode after 220 cycles.It is concluded that nanosized Fe_(2)(MoO_(4))_(3) could be promising alternative non-noble electro-catalysts for electro-oxidation of methanol in alkaline medium.