Olefin incorporation on supported FeCo alloy Fischer-Tropsch catalysts

We have previously reported on the properties of silicasupported Fe, Co and FeCo alloy for the Fischer-Tropsch (FT) reaction, both at atmospheric pressure and up to 14 atm (14 × 1·0133 × 10⁵ Pa). The selectivity for C₂−C₃ olefins reported in the literature for these catalysts (particularly FeCo) was found to be somewhat suppressed at higher pressures, although methanol production was enhanced. The present study is concerned with the possible role of olefin insertion on hydrocarbon chain growth and oxygenate production. Results for both ethylene and 1-pentene indicate some incorporation into the next higher carbon number product at low CO conversions, but not a significant effect on overall chain growth. There is a diminution of oxygenate formation with olefin-containing feeds for all catalysts and reaction conditions investigated (250°C, 1 and 7·8 atm). Present results do not exclude a role of olefin insertion in the mechanism of chain growth, but it seems to be a minor one at most. This paper is dedicated to Dr L K Doraiswamy on his sixtieth birthday. This research was supported by the Department of Energy, Office of Basic Energy Sciences, Contract DE-AC02-78ER04993.     

Comparison Between γ-Bi2MoO6 and Bi2WO6 Catalysts in the CO Oxidation

Bismuth molybdate (-Bi₂MoO₆) and bismuth tungstate (Bi₂WO₆) catalysts were prepared by solid-state reaction and their catalytic properties evaluated in the CO oxidation reaction. We characterize their structure by X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, and BET nitrogen absorption. X-ray diffraction analysis shows that both -Bi₂MoO₆ and Bi₂WO₆ are structural analogs (SG P2₁ ab). Auger analysis shows that Bi₂WO₆ catalysts have more bismuth on the surface than -Bi₂MoO₆, although both samples are bismuth deficient as compared to the stoichiometric compound. The results regarding catalytic activity show that Bi₂WO₆ prepared at 1073 K reaches total conversion of CO (100%) at a lower temperature when compared to -Bi₂MoO₆. It indicates that Bi₂WO₆ is a potential candidate to be used as catalyst in the CO to CO₂ oxidation.     

极性单体与烯烃共聚反应的研究进展

综述了Ziegler—Natta催化荆、茂金属催化荆及后过渡金属催化剂在极性单体与烯烃共聚合反应中的研究进展。展望了极性单体与烯烃共聚反应研究的发展方向。     

Electronic Structure Modulation of Nickel Sites by Cationic Heterostructures to Optimize Ethanol Electrooxidation Activity in Alkaline Solution

It is a good idea for efficient production of hydrogen to use ethanol oxidation reaction (EOR) in place of oxygen evolution reaction (OER) in water electrolysis process. Ni-based non-precious electrocatalysts are widely used in the conversion of ethanol to acetic acid. Here, different selenide heterostructures (NiCoSe, NiFeSe, and NiCuSe) are prepared in which Ni sites are regulated by transition metal. The valence state of Ni is NiCuSe < NiCoSe < NiFeSe in the three heterojunctions. NiCoSe shows the optimized charge distribution of Ni sites and outstanding catalytic activity. The effective modulations lead to optimized d-band center and facilitates both adsorption and desorption of reaction intermediates, which improves the kinetics of EOR. The results of this work prove that with appropriate designed catalyst it is possible to replace kinetically slow OER with faster EOR in water electrolysis to produce hydrogen.     

新型催化剂使聚烯烃重焕青春——金属茂催化剂最近进展

技术突破———金属茂或单活性点催化剂赋予聚烯烃巨大活力。采用新的催化剂及工艺，可使生产者通过严格控制聚合过程，设计制造结构均匀一致的产品，以满足用户对性能的要求。本文介绍此领域内合资经营和联合促进技术进步、现有装置应用新催化剂时易于改造、新催化剂在聚丙烯生产中的优势和最近的进展情况等。     

Single-Atom Catalysts and Dual-Atom Catalysts for CO2 Electroreduction: Competition or Cooperation?

Developing highly active and selective electrocatalysts for electrochemical reduction of CO₂ can reduce environmental pollution and mitigation of greenhouse gas emission. Owing to maximal atomic utilization, the atomically dispersed catalysts are broadly adopted in CO₂ reduction reaction (CO₂RR). Dual-atom catalysts (DACs), with more flexible active sites, distinct electronic structures, and synergetic interatomic interactions compared to single-atom catalysts (SACs), may have great potential to enhance catalytic performance. Nevertheless, most of the existing electrocatalysts have low activity and selectivity due to their high energy barrier. Herein, 15 electrocatalysts are explored with noble metallic (Cu, Ag, and Au) active sites embedded in metal–organic hybrids (MOHs) for high-performance CO₂RR and studied the relationship between SACs and DACs by first-principles calculation. The results indicated that the DACs have excellent electrocatalytic performance, and the moderate interaction between the single- and dual-atomic center can improve catalytic activity in CO₂RR. Four among the 15 catalysts, including (CuAu), (CuCu), Cu(CuCu), and Cu(CuAu) MOHs inherited a capability of suppressing the competitive hydrogen evolution reaction with favorable CO overpotential. This work not only reveals outstanding candidates for MOHs-based dual-atom CO₂RR electrocatalysts but also provides new theoretical insights into rationally designing 2D metallic electrocatalysts.     

Exceptional High‐Performance of Pt‐Based Bimetallic Catalysts for Exclusive Detection of Exhaled Biomarkers

Achieving an improved understanding of catalyst properties, with ability to predict new catalytic materials, is key to overcoming the inherent limitations of metal oxide based gas sensors associated with rather low sensitivity and selectivity, particularly under highly humid conditions. This study introduces newly designed bimetallic nanoparticles (NPs) employing bimetallic Pt‐based NPs (PtM, where M = Pd, Rh, and Ni) via a protein encapsulating route supported on mesoporous WO₃ nanofibers. These structures demonstrate unprecedented sensing performance for detecting target biomarkers (even at p.p.b. levels) in highly humid exhaled breath. Sensor arrays are further employed to enable pattern recognition capable of discriminating between simulated biomarkers and controlled breath. The results provide a new class of multicomponent catalytic materials, demonstrating potential for achieving reliable breath analysis sensing.     

肼类分解催化剂研究进展

肼分解催化剂主要应用于航天飞行器的单组元姿态控制发动机上,用以改变其飞行轨道或调整飞行姿态.介绍了姿控发动机及其工作原理和用途.在国内研究肼分解催化剂的进展方面,简介了我国研究肼分解催化剂的历程、取得的成果和近期的研究动态;国外方面,介绍了贵金属和非贵金属两类典型的肼类分解催化剂;还总结和分析了担载铱催化剂的催化机理及其失活原因,指出了当今催化剂存在的问题及实际发展的需求方向.     

Synthesis and investigation of bimetallic Ni-Co/Al2O3 nanocatalysts using the polyol process

ABSTRACT

Ni-Co/Al₂O₃ catalysts with different Ni:Co ratios by weight were prepared using a simple polyol process. The activities of the catalysts were evaluated for the catalytic partial oxidation of methane (CPOM) in the temperature range of 600–800°C. Numerous techniques such as x-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, inductively coupled plasma-mass spectroscopy (ICP-MS), thermogravimetric analysis (TGA), high-resolution transmission electron microscopy analysis (HRTEM), scanning electron microscopy analysis (SEM-EDS) and temperature-programmed oxidation (TPO) were applied to characterize fresh and spent catalysts. The XRD analysis confirmed that the loaded particles were metals and showed possible bimetallic nano-alloy Ni-Co formation for Ni- and Co-containing catalysts. The highest metal dispersion was 15.7% for the Ni_2.8Co_2.6/Al₂O₃ catalyst. The catalytic test results showed no correlation between metal dispersion and the metal particle size, and the activity decreased in the order of Ni_7.7/Al₂O₃ > Ni_2.8Co_2.6/Al₂O₃ ≈ Ni_3.8Co_1.5/Al₂O₃ > Ni_2.0Co_3.8/Al₂O₃ >> Co_6.8/Al₂O₃ under a flow rate of 157,500 L kg^?1 h^?1 with CH₄/O₂ = 2 (using air as an oxidant) at 800°C. The obtained results also showed that when the actual atomic Ni/Co ratio was 1.07 in the Al₂O₃-supported catalyst, the dispersion of the active sites appeared to be promoted by Co addition, and the catalytic activity was stable over a reaction time of 10 h. Among all the tested catalysts, the Ni_2.8Co_2.6/Al₂O₃ catalyst exhibited acceptable activity (75%) without coking.     

ZIF‐8 with Ferrocene Encapsulated: A Promising Precursor to Single‐Atom Fe Embedded Nitrogen‐Doped Carbon as Highly Efficient Catalyst for Oxygen Electroreduction

The oxygen reduction reaction (ORR) plays an important role in the fields of energy storage and conversion technologies, including metal–air batteries and fuel cells. The development of nonprecious metal electrocatalysts with both high ORR activity and durability to replace the currently used costly Pt‐based catalyst is critical and still a major challenge. Herein, a facile and scalable method is reported to prepare ZIF‐8 with single ferrocene molecules trapped within its cavities (Fc@ZIF‐8), which is utilized as precursor to porous single‐atom Fe embedded nitrogen‐doped carbon (Fe–N–C) during high temperature pyrolysis. The catalyst shows a half‐wave potential (E_1/2) of 0.904 V, 67 mV higher than commercial Pt/C catalyst (0.837 V), which is among the best compared with reported results for ORR. Significant electrochemical properties are attributed to the special configuration of Fc@ZIF‐8 transforming into a highly dispersed iron–nitrogen coordination moieties embedded carbon matrix.     

微波辐射下PET解聚的醋酸盐系催化作用研究

在研究纯水中微波解聚PET的有机类催化剂的基础上，进一步研究了醋酸盐系催化剂对PET微波解聚的催化作用，实验结果表明，醋酸锌对微波作用下PET的解聚有催化效果，且有效催化的用量范围是0．15％～0．6％。     

新型高分子手性催化剂

介绍了一种新型高分子手性催化剂及不对称合成反应，催化剂在不对称合成反应中的应用以及初步验证实验。     

Iron‐Free Cathode Catalysts for Proton‐Exchange‐Membrane Fuel Cells: Cobalt Catalysts and the Peroxide Mitigation Approach

High‐performance and inexpensive platinum‐group‐metal (PGM)‐free catalysts for the oxygen reduction reaction (ORR) in challenging acidic media are crucial for proton‐exchange‐membrane fuel cells (PEMFCs). Catalysts based on Fe and N codoped carbon (Fe–N–C) have demonstrated promising activity and stability. However, a serious concern is the Fenton reactions between Fe²⁺ and H₂O₂ generating active free radicals, which likely cause degradation of the catalysts, organic ionomers within electrodes, and polymer membranes used in PEMFCs. Alternatively, Co–N–C catalysts with mitigated Fenton reactions have been explored as a promising replacement for Fe and PGM catalysts. Therefore, herein, the focus is on Co–N–C catalysts for the ORR relevant to PEMFC applications. Catalyst synthesis, structure/morphology, activity and stability improvement, and reaction mechanisms are discussed in detail. Combining experimental and theoretical understanding, the aim is to elucidate the structure–property correlations and provide guidance for rational design of advanced Co catalysts with a special emphasis on atomically dispersed single‐metal‐site catalysts. In the meantime, to reduce H₂O₂ generation during the ORR on the Co catalysts, potential strategies are outlined to minimize the detrimental effect on fuel cell durability.     

PGM‐Free Cathode Catalysts for PEM Fuel Cells: A Mini‐Review on Stability Challenges

In recent years, significant progress has been achieved in the development of platinum group metal‐free (PGM‐free) oxygen reduction reaction (ORR) catalysts for proton exchange membrane (PEM) fuel cells. At the same time the limited durability of these catalysts remains a great challenge that needs to be addressed. This mini‐review summarizes the recent progress in understanding the main causes of instability of PGM‐free ORR catalysts in acidic environments, focusing on transition metal/nitrogen codoped systems (M‐N‐C catalysts, M: Fe, Co, Mn), particularly MN_x moiety active sites. Of several possible degradation mechanisms, demetalation and carbon oxidation are found to be the most likely reasons for M‐N‐C catalysts/cathodes degradation.     

Graphene-Encapsulated Bifunctional Catalysts with High Activity and Durability for Zn–Air Battery

Carbon-based electrocatalysts with both high activity and high stability are desirable for use in Zn–air batteries. However, the carbon corrosion reaction (CCR) is a critical obstacle in rechargeable Zn–air batteries. In this study, a cost-effective carbon-based novel material is reported with a high catalytic effect and good durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), prepared via a simple graphitization process. In situ growth of graphene is utilized in a 3D-metal-coordinated hydrogel by introducing a catalytic lattice of transition metal alloys. Due to the direct growth of few-layer graphene on the metal alloy decorated 3d-carbon network, greatly reduced CCR is observed in a repetitive OER test. As a result, an efficient bifunctional electrocatalytic performance is achieved with a low ΔE value of 0.63 V and good electrochemical durability for 83 h at a current density of 10 mA cm⁻² in an alkaline media. Moreover, graphene-encapsulated transition metal alloys on the nitrogen-doped carbon supporter exhibit an excellent catalytic effect and good durability in a Zn–air battery system. This study suggests a straightforward way to overcome the CCR of carbon-based materials for an electrochemical catalyst with wide application in energy conversion and energy storage devices.     

Dual-Active-Sites Single-Atom Catalysts for Advanced Applications

Dual-Active-Sites Single-Atom catalysts (DASs SACs) are not only the improvement of SACs but also the expansion of dual-atom catalysts. The DASs SACs contains dual active sites, one of which is a single atomic active site, and the other active site can be a single atom or other type of active site, endowing DASs SACs with excellent catalytic performance and a wide range of applications. The DASs SACs are categorized into seven types, including the neighboring mono metallic DASs SACs, bonded DASs SACs, non-bonded DASs SACs, bridged DASs SACs, asymmetric DASs SACs, metal and nonmetal combined DASs SACs and space separated DASs SACs. Based on the above classification, the general methods for the preparation of DASs SACs are comprehensively described, especially their structural characteristics are discussed in detail. Meanwhile, the in-depth assessments of DASs SACs for variety applications including electrocatalysis, thermocatalysis and photocatalysis are provided, as well as their unique catalytic mechanism are addressed. Moreover, the prospects and challenges for DASs SACs and related applications are highlighted. The authors believe the great expectations for DASs SACs, and this review will provide novel conceptual and methodological perspectives and exciting opportunities for further development and application of DASs SACs.     

Au/CuSiO<Subscript>3</Subscript> nanotubes: High-performance robust catalysts for selective oxidation of ethanol to acetaldehyde

Novel gold-supporting silicate nanotubes are synthesized via a hydrothermal method followed by colloid deposition. Their catalytic performance for the selective oxidation of ethanol to acetaldehyde is assessed. The results show that Au/CuSiO₃ nanotubes exhibit both high activity and selectivity at high gas hourly space velocity (GHSV). Ethanol conversion can reach up to ~98%, and the selectivity for acetaldehyde is ~93% at 250 °C and ~100,000 mL·gcat^–1·h^–1. In comparison, the catalytic activity of Au/MgSiO₃ nanotubes is relatively low, and ethanol conversion reaches only ~25% at 250 °C. However, when Cu species are added to Au/MgSiO₃, the catalytic activity improves significantly, indicating that the interactions between Au nanoparticles and Cu species are responsible for the high performance for selective oxidation of ethanol to acetaldehyde.

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