Thermally Evaporated Ag–Au Bimetallic Catalysts for Efficient Electrochemical CO2 Reduction

CO₂ reduction reaction (CO₂RR) has indispensable significance for carbon recycling and renewable energy production. As typical electrochemical catalysts, Au and Ag show relatively high reaction activity and selectivity in CO₂RR. In this study, a series of Ag–Au bimetallic catalysts are designed and synthesized through the thermal evaporation method for efficient yet massive production of electrochemical catalysts. The Ag–Au catalysts show significantly enhanced activity and selectivity in CO₂RR, which is mainly attributed to the increased grain boundaries with well-dispersed single Ag atoms. After the optimization, Au20Ag10 exhibits the best performance with a CO Faraday efficiency of 89% at −0.9 V (vs the reversible hydrogen electrode) with good stability.     

Progress in thermal-mechantical effects induced by laser

对激光辐照诱导的热与力学问题研究进展进行了综述,包括材料在高温、高升温速率下的本构关系,典型薄板和柱壳等结构在激光辐照下的热力破坏效应,多层材料体系的激光破坏行为等几个方面,并着重介绍了包含相变与烧蚀过程的激光破坏分析模型与机制研究,激光辐照效应的流-热-固耦合数值模拟方法,以及短脉冲激光引起的冲击与破坏机理等方面的研究新进展.     

Correlation of the Catalytic Activity for Oxidation Taking Place on Various TiO2 Surfaces with Surface OH Groups and Surface Oxygen Vacancies

Three catalytic oxidation reactions have been studied: The ultraviolet (UV) light induced photocatalytic decomposition of the synthetic dye sulforhodamine B (SRB) in the presence of TiO₂ nanostructures in water, together with two reactions employing Au/TiO₂ nanostructure catalysts, namely, CO oxidation in air and the decomposition of formaldehyde under visible light irradiation. Four kinds of TiO₂ nanotubes and nanorods with different phases and compositions were prepared for this study, and gold nanoparticle (Au‐NP) catalysts were supported on some of these TiO₂ nanostructures (to form Au/TiO₂ catalysts). FTIR emission spectroscopy (IES) measurements provided evidence that the order of the surface OH regeneration ability of the four types of TiO₂ nanostructures studied gave the same trend as the catalytic activities of the TiO₂ nanostructures or their respective Au/TiO₂ catalysts for the three oxidation reactions. Both IES and X‐ray photoelectron spectroscopy (XPS) proved that anatase TiO₂ had the strongest OH regeneration ability among the four types of TiO₂ phases or compositions. Based on these results, a model for the surface OH group generation, absorption, and activation of molecular oxygen has been proposed: The oxygen vacancies at the bridging O^2? sites on TiO₂ surfaces dissociatively absorb water molecules to form OH groups that facilitate adsorption and activation of O₂ molecules in nearby oxygen vacancies by lowering the absorption energy of molecular O₂. A new mechanism for the photocatalytic formaldehyde decomposition with the Au/TiO₂ catalysts is also proposed, based on the photocatalytic activity of the Au‐NPs under visible light. The Au‐NPs absorb the light owing to the surface plasmon resonance effect and mediate the electron transfers that the reaction needs.     

聚乙二醇介质中纳米铁基催化剂上的费托合成

 采用化学还原法在纯水中制备了纳米铁基催化剂, 将其直接分散到液态聚乙二醇 (PEG) 中进行费托合成 (FTS) 反应. 透射电子显微镜、X 射线衍射、穆斯堡尔谱和 X 射线光电子能谱等结果表明, 还原态催化剂粒径在 30~65 nm, 主要由无定形的 Fe-B 和α-Fe 组成, 其中 B 部分电子向 Fe 转移. 反应过程中, 无定形的 Fe-B 首先快速转变为 α-Fe, 而 α-Fe 很容易发生碳化或氧化, 最终转变为 Fe3O4 和碳化铁. PEG 能有效抑制纳米粒子的聚集长大, 反应后催化剂粒径减小为 20~55 nm. 在 3.0 MPa, V( H2)/V(CO) = 2 和 200 oC 的反应条件下, 该催化剂表现出优异的 FTS 低温活性和较高的稳定性, 反应后产物和催化体系很容易实现分离.     

费托合成 Fe基催化剂中铁物相与活性的关系

 采用连续共沉淀和喷雾干燥相结合的方法制备了微球形 Fe 基催化剂, 采用 N2 吸附-脱附、X 射线衍射和穆斯堡尔谱等手段, 考察了催化剂在不同还原条件下铁物相的转变, 并在浆态床反应器中评价了催化剂的费-托合成 (FTS) 反应性能. 结果表明, Fe 基催化剂在合成气气氛下首先从α-Fe2O3 转变为 Fe3O4, 然后转变为铁碳化物 (FexC); 还原压力的增大有利于 α-Fe2O3 向 Fe3O4 的转变, 而抑制 Fe3O4 向 FexC 的转变; 还原空速的增加则促进 Fe3O4 转变为 FexC. 催化剂的 FTS 反应活性随着催化剂中 Fe3O4 含量的增加而逐渐下降, 而随着 FexC 含量的增加而逐渐上升.     

The quantitative monitoring of mechanochemical reaction between solid l-tartaric acid and sodium carbonate monohydrate by terahertz spectroscopy

The solid-state reaction of chiral tartaric acid and alkali carbonate was studied by terahertz time-domain spectroscopy (THz-TDS). The sodium tartrate dihydrate was synthesized with high efficiency by mechanical grinding in the solid-state without waste that is particularly sustainable and environmentally benign. Distinct THz absorptions were observed for reactants and products. It indicates that THz spectroscopy is sensitive to different materials and crystal structures. The characteristic THz absorption peak at 1.09 THz of l (+)-Tartaric acid was selected for quantitative analysis. The reaction kinetics could be expressed by the Second-order equation and the Jander equation, which is consistent with a three-dimensional diffusion mechanism. The combination of multi-techniques including synchrotron radiation X-ray powder diffraction (SRXRPD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) was used to investigate the grinding process and presented supporting evidences. The results demonstrate that THz spectroscopy technique has great potential applications in process monitoring and analysis in pharmaceutical and chemical synthesis industry.     

大功率固态脉冲形成线研究进展

 固态化是脉冲功率技术发展的新趋势。综述了中国工程物理研究院流体物理研究所在大功率固态脉冲形成线方面的研究进展,给出了基于铁电陶瓷及玻璃-陶瓷复合材料的固态脉冲形成线绝缘强度、脉冲放电特性等方面的最新结果。对基于铁电陶瓷及玻璃-陶瓷复合材料的固态脉冲形成线的脉冲特性进行了分析和探索。     

体结构GaAs光导开关实验研究

 为解决光导开关耐受场强的提高问题,研制了2种体结构光导开关,并进行了实验研究。两种开关均由半绝缘GaAs材料制成,一种尺寸为10.0 mm×10.0 mm×0.6 mm,电极位于10.0 mm×10.0 mm面上相对位置,电极直径6 mm;另一种尺寸为15.0 mm×15.0 mm×3.0 mm,8 mm直径电极位于15.0 mm×15.0 mm面上相对位置。测试了第1种开关在不同半高宽脉冲加载电压下的击穿电压,结果表明其最大耐受电压达7.6 kV,击穿电场127 kV/cm。对第2种结构测试了开关在直流加载条件下的暗态伏安特性并进行了触发实验,结果表明在15 kV工作电压下,其放电最大电流超过3.5 kA。     

First-principle study of NO adsorption on the LaFeO3 (0 1 0) surface

The adsorption of NO molecule on the LaFeO₃ (0 1 0) surface was studied using first-principle calculations based on density functional theory. The calculated results indicate that the Fe-top site is the most favorable for NO adsorption. The N-O bond length, Mulliken charge, and the N-O vibration frequency of the NO molecule are discussed after adsorption. The analysis results of the density of the states show that when NO is adsorbed with the Fe-NO configuration, the bonding mechanism is mainly from the interaction between the NO and the Fe d orbit.     

Photocatalytic performance of ZnO:Fe array films under sunlight irradiation

ZnO:Fe array thin films were prepared by the hydrothermal method using the sol-gel grown film as a seed layer. The samples were characterized by X-ray diffraction (XRD), ultraviolet/visible absorption spectra (UV-vis) and scanning electron microscopy (SEM). The photocatalytic activities of the prepared samples were investigated for the photodegradation of methylene blue (MB) under sunlight irradiation. The results show that the lattice constant a and the cell volume of ZnO:Fe film increase due to the substitution of Fe for Zn. The absorption edge of Fe-doped ZnO displays a red shift with a significant absorption between 600 and 700 nm. The ZnO:Fe array film is composed of disk particles with uniformity and compactness. Doping Fe ions enhances the photodegradation rate of ZnO array film for MB. 1.5% Fe doped ZnO sample exhibits the highest activity under irradiation time of 4 h. Its degradation rate increases about 1.6 times compared to the undoped ZnO.