Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles

Nanoparticles of cobalt phosphide, CoP, have been prepared and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) under strongly acidic conditions (0.50 M H₂SO₄, pH 0.3). Uniform, multi‐faceted CoP nanoparticles were synthesized by reacting Co nanoparticles with trioctylphosphine. Electrodes comprised of CoP nanoparticles on a Ti support (2 mg cm^?2 mass loading) produced a cathodic current density of 20 mA cm^?2 at an overpotential of ?85 mV. The CoP/Ti electrodes were stable over 24 h of sustained hydrogen production in 0.50 M H₂SO₄. The activity was essentially unchanged after 400 cyclic voltammetric sweeps, suggesting long‐term viability under operating conditions. CoP is therefore amongst the most active, acid‐stable, earth‐abundant HER electrocatalysts reported to date.     

由非晶态Ni-P低温制备Ni2P催化剂及其对二苯并噻吩加氢脱硫的催化性能

 以非晶态Ni-P合金为前驱体,在低温下通过PH3处理制备了Ni2P/SiO2-Al2O3催化剂,并用X射线衍射(XRD)、 透射电镜(TEM)、 电感耦合等离子体发射光谱、 N2吸附和X射线光电子能谱(XPS)进行了表征,以二苯并噻吩为探针,在小型连续流动固定床反应器上考察了催化剂的加氢脱硫性能. XRD结果表明,在200～300 ℃范围内前驱体都可以完全转化为Ni2P, 随着磷化温度的升高,晶体结构变得越来越完整. TEM观察发现, Ni-P粒子和Ni2P粒子的平均尺寸都在40～50 nm, 并且都能够高分散在SiO2-Al2O3载体上. XPS结果表明,不论是非负载还是SiO2-Al2O3负载的Ni2P, 表层主要为Ni2P和钝化层Ni3(PO4)2. Ni2P/SiO2-Al2O3催化剂在实验范围内表现出很好的二苯并噻吩加氢脱硫性能.     

TiO2-Al2O3载体的制备及Ni2P/TiO2-Al2O3催化剂上的同时加氢脱硫和加氢脱氮反应

 以溶胶-凝胶法制备的 TiO2-Al2O3 复合氧化物为载体, 采用浸渍法制备了 Ni2P/TiO2-Al2O3 催化剂, 并用 X 射线衍射、N2 吸附脱附、红外和 X 射线光电子能谱等技术对催化剂进行了表征, 考察了载体中 TiO2 含量、焙烧温度及其制备方法对 Ni2P/TiO2-Al2O3 催化剂上同时进行噻吩加氢脱硫和吡啶加氢脱氮反应的影响. 结果表明, 以 Ni/P 摩尔比为 1/2 的前驱体制备的催化剂表面仅出现 Ni2P 物相; 当载体中 TiO2 的含量为 80%, 焙烧温度为 550 oC 时, Ni2P/TiO2-Al2O3 催化剂上加氢脱硫和加氢脱氮的活性最高. 在 360 oC, 3.0 MPa, 氢/油体积比 500, 液时体积空速 2.0 h?1 的条件下, 噻吩和吡啶转化率分别为 61.3%和 64.4%.     

Ellipsometric analysis and optical absorption characterization of gallium phosphide nanoparticulate thin film

Gallium phosphide (GaP) nanoparticulate thin films were easily fabricated by colloidal suspension deposition via GaP nanoparticles dispersed in N,N-dimethylformamide. The microstructure of the film was performed by x-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy. The film was further investigated by spectroscopic ellipsometry. After the model GaP+void|SiO₂ was built and an effective medium approximation was adopted, the values of the refractive index n and the extinction coefficient k were calculated for the energy range of 0.75 eV-4.0 eV using the dispersion formula in DeltaPsi2 software. The absorption coefficient of the film was calculated from its k and its energy gaps were further estimated according to the Tauc equation, which were further verified by its fluorescence spectrum measurement. The structure and optical absorption properties of the nanoparticulate films are promising for their potential applications in hybrid solar cells.     

Synergetic effects during sputter-assisted depth profiling: Growth-dominated topography development on InP and a model of the atomic mechanism

Growth-dominated extreme topography development on ionbombarded wafers of InP is reported and is explained in terms of the micro region model presented in summary form. This model postulates the existence of an ion-bombardment-produced ensemble of crystallites and non-crystalline aggregations of atoms (composed of the substrate material, of dopant and of oxygen from the native oxide layer) where the majority of InP micro regions is so small (nanometer dimensions) that most interstitials created in collision events between bombarding ions and atoms of the micro region can reach an interfacial boundary rather than recombine with a vacancy from the same or another collision event. These atoms are then transported via interfacial boundaries and over the surface to screw dislocations where crystal stubs proceed to grow until the damage rate by ion bombardment overtakes the growth rate. Ion-bombardment-induced compressive stresses favour diffusion towards the surface. Temperature transients within micro regions assist both interfacial diffusion and damage repair. The topography is a result of competition between growth and sputtering. Different growth rates cause different topographies. The development of an extreme topography can be suppressed by oxygen flooding of the sputtered surface, by simultaneous electron beam scanning, as well as by Cs⁺ ion bombardment.     

The emission wavelength tuning of InAs/InP quantum dots with thin GaAs, InGaAs, InP capping layers by MOCVD

InAs quantum dots (QDs) were grown on InP substrates by metalorganic chemical vapor deposition. The width and height of the dots were 50 and 5.8 nm, respectively on the average and an areal density of 3.0×10¹⁰ cm⁻² was observed by atomic force microscopy before the capping process. The influences of GaAs, In_0.53Ga_0.47As, and InP capping layers (5–10 ML thickness) on the InAs/InP QDs were studied. Insertion of a thin GaAs capping layer on the QDs led to a blue shift of up to 146 meV of the photoluminescence (PL) peak and an InGaAs capping layer on the QDs led to a red shift of 64 meV relative to the case when a conventional InP capping layer was used. We were able to tune the emission wavelength of the InAs QDs from 1.43 to 1.89 μm by using the GaAs and InGaAs capping layers. In addition, the full-width at half-maximum of the PL peak decreased from 79 to 26 meV by inserting a 7.5 ML GaAs layer. It is believed that this technique is useful in tailoring the optical properties of the InAs QDs at mid-infrared regime.     

Electrochemical formation of porous superlattices on n-type (1 0 0) InP

The present work deals with the electrochemical formation of superlattice structures on n-type (1 0 0) InP in HCl solutions. The superlattices consist of a stack of two layers with alternating high and low porosity on n-type material obtained by changing the anodizing current or the potential periodically in HCl solutions. The superlattice structures were characterized by scanning electron microscopy. The pore morphology and structure depend strongly on the electrochemical conditions. For anodization with low currents (e.g., 1 or 10 mA) or at low potentials (e.g., 1.5 V_Ag/AgCl), a porous layer with a facet-like structure was formed. For higher currents or potentials, such as 50 or 100 mA or 3 V_Ag/AgCl, respectively, a tree-like structure with random and/or tangled branches was observed. Finally, samples anodized at 5 V_Ag/AgCl, show a porous layer with a regular array of straight pores. The morphology and structure of the stacks of the porous layers can be controlled in the nanometer range, depending on the electrochemical conditions.     

含镍WP/MCM-41催化剂二苯并噻吩加氢脱硫性能

以MCM-41为载体,以镍（Ni）为助剂,制备了Ni含量不同的WP/MCM-41催化剂。采用XRD、BET、SEM和XPS对催化剂进行了表征;以二苯并噻吩（DBT）为模型化合物,通过高压微反装置考察催化剂的加氢脱硫（HDS）活性。结果表明,Ni的加入促进了活性组分WP的生长并使其晶相尺寸略有增加,一定含量的Ni有利于提高催化剂的比表面积。Ni对WP/MCM-41催化剂二苯并噻吩HDS反应具有促进作用。少量Ni的加入有利于WP活性相的生成并增加了活性位的数量;加入过量的Ni,在催化剂中形成了具有一定活性的类似Ni-W-P结构的物种,减少了活性组分WP所占的比例,从而使催化剂DBT的 HDS活性降低。其中,Ni的质量分数为1%的催化剂（cat-Ni-1）具有相对较高活性,其DBT 脱硫率和转化率分别为76.78%和72.16%,比不加Ni的催化剂分别提高了30.04%和21.62%。二苯并噻吩在WP/MCM-41催化剂上以加氢脱硫途径为主,Ni的加入对提高加氢脱硫途径选择性起到了促进作用,且加氢脱硫选择性随Ni含量的增加而提高。     

Synthesis of Ni2P promoted trimetallic NiMoW/γ-Al2O3 catalysts for diesel oil hydrotreatment

The Ni2P promoted and γ-Al2O3 supported NiMoW sulfide catalyst consisting of 4 wt% Mo, 22 wt% W, 2 wt% Ni and 2.5 wt% Ni2P was synthesized by a co-impregnation method. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, NH3 temperature-programmed desorption (NH3-TPD) and transmission electron microscopy (TEM). The results showed that Ni2P, Ni, Mo and W species were highly dispersed over γ-Al2O3. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) showed that the presence of Ni2P brought a strong promotional effect on the HDS activity, which was further confirmed by the HDS and hydrodenitrogenation (HDN) of diesel oil under industrial conditions. The enhancement in HDN activity and stability by Ni2P addition could be attributed more to the effect of new active sites of Ni2P than that of acidity modification. The as-prepared Ni2P-NiMoW/γ-Al2O3 catalyst showed better hydrotreating performance than NiMoW/γ-Al2O3 and commercial catalysts.