Theoretical study of the polarized electronic absorption spectra of vanadium-doped zircon

The polarized electronic absorption spectra of a blue vanadium-doped zircon single crystal, grown by the flux method, has been studied by quantum chemical (CI) calculations in order to determine the position of the V⁴⁺ dopant in the zircon host structure. Particularly, the excitation energies and polarizations of V⁴⁺ occupying alternate positions, either the zirconium or silicon position or the interstitial site 16g, have been considered. It is concluded that the observed electronic absorption spectra and the color of zirconblue can only be explained if the V⁴⁺ chromophore is placed on the respective interstitial position.     

RuO2修饰纳米多孔Ni-Mo复合电极及其电催化析氢性能

采用脱合金化结合胶体聚沉的方法制备了纳米多孔Ni/RuO_2、Ni-Mo/RuO_2复合电极材料。通过X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)、透射电镜(TEM)对电极材料的物相、元素组态、形貌结构、孔径大小和结晶度进行表征,并通过线性扫描伏安、交流阻抗以及循环伏安等方法测试多孔电极的电催化析氢性能。分析结果显示:RuO_2由于聚沉作用包覆在Ni基合金的骨架表面。Mo的加入使Ni-Mo合金非晶化的同时,促使其骨架细化,形成双连续的纳米多孔结构。Mo与RuO_2的加入以及Mo含量的增加均提高了电催化析氢性能。纳米多孔Ni_(2.5)Mo_(2.5)/RuO_2复合电极在50 mA·cm~(-2)的电流密度下析氢过电位为182 mV。     

全固态Z-Scheme光催化材料应用于二氧化碳还原和光催化分解水研究进展

由两种不同的半导体催化剂和电子传输介质建立的Z-Scheme光催化体系,通过在可见光照射下分别在两种半导体催化剂上进行氧化反应和还原反应,实现两步法光催化分解水和二氧化碳还原.相较于离子型Z-Scheme光催化体系,全固态Z-Scheme光催化体系具有适用范围广、无副反应、光源利用率高等特性,具有更加广阔的应用前景.在此,我们简述了Z-Scheme光催化体系的反应机理,综述了全固态Z-Scheme光催化体系在光催化分解水和光催化还原CO₂领域的应用,并对未来全固态Z-Scheme光催化体系的发展进行了展望.     

富氮洋葱碳包覆的Ni/NiFe2O4纳米棒析氧电催化剂

将镍铁金属配位聚合物前驱体在惰性气氛下热分解制备了富氮洋葱碳(ONC)包覆的Ni/Ni Fe_2O_4多孔纳米棒复合析氧电催化剂,与Ni@ONC,Ni Fe_2O_4材料及传统Ru O_2催化剂相比,得益于这种富氮洋葱碳包覆的Ni/Ni Fe_2O_4一维多孔纳米异质结构,Ni/Ni Fe_2O_4@ONC材料拥有更优异的导电性能和更大的电化学活性面积(0.149 m F),因而表现出更优异的析氧电催化性能。Ni/Ni Fe_2O_4@ONC纳米棒在1 mol·L~(-1) KOH溶液中,10 m A·cm-2下的析氧过电位仅为299 m V,塔菲尔斜率为73 m V·dec-1,展现出优异的析氧稳定性能。     

一锅法合成Ce_xZr_(1-x)O_2固溶体催化剂用于热化学循环分解CO_2制CO

采用一锅蒸发诱导自组装法(EISA)制备了一系列不同铈锆物质的量比的铈锆固溶体催化剂,用TGA研究了其热化学循环分解CO_2制CO的催化性能,并采用XRD、Raman光谱、H2-TPR、XPS、SEM和N_2吸附-脱附等手段对催化剂的物相结构、还原性能和表面化学性质进行了表征分析,用热重分析(TGA)研究了铈锆固溶体对热化学循环分解CO_2制CO的催化性能。结果表明,随着Ce/Zr物质的量比增加,铈锆固溶体催化剂的CO_2高温分解活性先增大后减小。Ce/Zr物质的量比为1的Ce_(0.5)Zr_(0.5)O_2催化剂由于具有较多的晶格缺陷和氧空穴,氧迁移能力强,催化活性高,而Ce/Zr物质的量比为3的Ce_(0.75)Zr_(0.25)O_2催化剂具有相对稳定的氧空穴数,循环稳定性好。循环反应后,所有的催化剂均出现了一定程度的烧结,且富锆固溶体发生了相分离,这可能会影响催化剂的性能。     

Highly Dispersed and Small‐Sized Nickel(II) Hydroxide Co‐Catalyst Prepared by Photodeposition for Hydrogen Production

Photodeposition has been widely used as a mild and efficient synthetic method to deposit co‐catalysts. It is also worth studying how to synthesize non‐noble metal photocatalysts with uniform dispersion. Different synthetic conditions in photodeposition have a certain influence on particle size distribution and photocatalytic activity. Therefore, we designed experiments to prepare the inexpensive composite photocatalyst Ni(OH)₂/g‐C₃N₄ by photodeposition. The Ni(OH)₂ co‐catalysts disperse uniformly with particle sizes of about 10 nm. The photocatalytic hydrogen production rate of Ni(OH)₂/g‐C₃N₄ reached about 19 mmol g^?1 h^?1, with the Ni(OH)₂ deposition amount about 1.57 %. During 16 h stability testing, the rate of hydrogen production did not decrease significantly. The composite catalyst also revealed a good hydrogen production performance under sunlight. The Ni(OH)₂ co‐catalyst enhanced the separation ability of photogenerated carriers, which was proved by surface photovoltage and fluorescence analysis.     

A Polypyridyl‐Based Layered Complex as Dual‐Functional Co‐catalyst for Photo‐Driven Organic Dyes Degradation and Water Splitting

With the ever‐increasing concerns on environmental pollution and energy crisis, it is of great urgency to develop high‐performance photocatalyst to eliminate organic pollutants from wastewater and produce hydrogen via water splitting. Herein, a polypyridyl‐based mixed covalent Cu^I/II complex with triangular {Cu₃} and rhombic {Cu₂Cl₄} subunits alternately extended by mixed SCN^– and Cl^– heterobridges [Cu₄(DNP)(SCN)Cl₄]_n ( 1 ) [DNP = 2,6‐bis(1,8‐naphthyridine‐2‐yl)pyridine] was solvothermally synthesized and employed as a dual‐functional co‐photocatalyst. Resulting from a narrowed band‐gap of 1.07 eV with suitable redox potential and unsaturated Cu^I/II sites, the complex together with H₂O₂ can effectively degrade Rhodamine B and methyl orange up to 87.4 and 88.2 %, respectively. Meanwhile, the complex mixed with H₂PtCl₆ can also accelerate the photocatalytic water splitting in the absence of a photosensitizer with the hydrogen production rate of 27.5 μmol · g^–1 · h^–1. These interesting findings may provide informative hints for the design of the multiple responsive photocatalysts.     

呋喃西林水溶液在光和热作用下的稳定性

The influence of both light and heat on the stability of nitrofurazone aqueous solution was studied. Results show that in either heating experiments or the exposure to light at high temperatures, the degradation rate obeyed zero-order kinetics. The total rate constant ktotal caused by both light and heat can be divided into two parts: ktotal =kdark klight, where kdark and klight are the degradation rate constants caused by heat and light, respectively. The klight can be expressed as klight=Alight*exp(-Ea,light/RT)*E, where E is the illuminance of light, and Alight and Ea,light both are experimental constants. The values of these kinetic parameters were determined based on the experiments in the dark and upon exposure to three different light sources. Results show that the values of Alight and Ea, light varied with the light source. To save time, labor, and drugs, exponential heating experiments were employed and compared with the isothermal experiments. Results indicated that kinetic parameters obtained by exponential heating experiments are comparable to those obtained by isothermal experiments either in the dark or upon exposure to light.     

A Kinetic Evidence for the Nitroxyl Radicals Recycling Mechanism in the Photostabilizing Process of HALS

The photoinduced bulk polymerization of a reactive-hindered amine fight stabilizers(r-HALS), 4-acryloyl-2, 2, 6, 6-tetramethylpiperidinyl (ATMP), was performed at 80℃ by using a DPC technique. An unique periodic exponential attenuation-type oscillating curve was found when the polymerization was carried out in air, but this phenomenon was not found in nitrogen.It is supposed that this unique kinetic performance may be attributed to nitroxyl radicals that are produced in situ from the oxidation of ATMP. ATMP polymer with narrow polydispersity (d =1.03) can be obtained by photoinduced solution polymerization of ATMP. The signal detected in ESR may be assigned to the nitroxyl radicals in the matrix of ATMP polymer. Since this kind of recycling of nitroxyl radicals is well documented for the photostabilizing mechanism of HALS, the present results may serve as a kinetic evidence for this mechanism.     

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.