热处理温度对锂氧气电池用Co-N/C催化剂催化性能的影响

开发低成本、高效的空气电极催化剂是发展锂空气电池的关键课题之一. 采用邻菲咯啉(phen)为配体制备Co(phen)₂配合物,负载于BP2000 碳载体上,并分别在600、700、800 和900 ℃的温度下进行热处理,制备得到碳支撑的Co-N催化剂(Co-N/C). 对催化剂的氧还原反应/析氧反应(ORR/OER)活性进行了表征,并且与典型的CoTMPP/C催化剂进行了比较. 同时研究了煅烧温度对Co-N/C催化剂的组成和结构的影响. 电化学测试结果表明,热处理温度为700-800 ℃时催化剂具有较好的电化学性能. Co-N/C催化剂具有电化学性能优良与低成本的特点,是一种良好的锂氧气电池催化剂.     

Synthesis of amides through the Cannizzaro-type reaction catalyzed by lanthanide chlorides

Amidation of aldehydes with lithium amides through the LnCl₃-catalyzed Cannizzaro-type reactions afforded a variety of amides in high yields. The electronic and steric effects on the reaction were investigated. The features of the economical catalysts, high yields, tolerance of a wide range of lithium amides and aromatic aldehydes make this methodology an easy and valid contribution to the direct synthesis of amides from aldehydes.     

乙烷PBI/H_3PO_4质子传导膜燃料电池性能

研究了以乙烷作为燃料、掺杂了H3PO4的聚苯并咪唑(PBI)材料作为质子传导膜、Pt/C作为电极催化剂构成的燃料电池电化学性能。采用溶液铸造法制备了PBI/H3PO4质子传导膜,考察了在PBI膜中H3PO4的掺杂量与时间的关系及乙烷气体在增湿和不增湿条件下PBI/H3PO4燃料电池的电化学性能;探讨了电池的反应机理及不同操作温度对电池性能的影响。结果表明,PBI膜H3PO4适宜的掺杂时间为8h,电解质中掺杂600mol%H3PO4;乙烷气体增湿后,电池性能变好;操作温度提高,电化学反应速率加快,电池的输出电流与功率密度增加。结构为C2H6,(Pt/C阳极)/PBI/H3PO4膜/(Pt/C阴极),O2的单电池,在200℃和0.1Mpa、乙烷气体的湿度从0增加到0.02kgH2O/kg乙烷时,电池的最大输出电流密度从1.5mA·cm-2增加到34mA·cm-2,最大功率密度从0.33mW·cm-2增加到5.5mW·cm-2。     

Fe2O3-Li2O Catalysts for Ammonia Oxidation

The catalytic properties of the Fe₂O₃-Li₂O system in ammonia oxidation were studied in the high-temperature region. The influence of the phase composition of the system on the physicochemical, catalyticproperties of the catalysts were revealed. The catalytic properties of lithium ferrite, which is the most activeand selective component of the Fe₂O₃-Li₂O system, were studied. The mechanism of lithium ferrite deactivation at 1273 K is considered.     

Preparation of hydrogen for feeding fuel cells by low-temperature conversion of ethanol on Ni/ZnO and Ni-Cu/ZnO catalysts

Preparation of hydrogen by low-temperature steam conversion of ethanol on nickel and binary nickel-copper catalysts supported on zinc oxide was studied experimentally in the temperature interval 200–450°C. High efficiency of hydrogen evolution in the course of ethanol conversion on these catalysts was demonstrated. At temperatures lower than 350°C, the main conversion products are hydrogen, methane, carbon monoxide, and carbon dioxide. At 400°C, the conversion products contain no carbon monoxide, which allows the mixture obtained to be used for feeding fuel cells with proton-conducting membranes.     

Comparing Neutral (Monometallic) and Anionic (Bimetallic) Aluminum Complexes in Hydroboration Catalysis: Influences of Lithium Cooperation and Ligand Set

Bimetallic lithium aluminates and neutral aluminum counterparts are compared as catalysts in hydroboration reactions with aldehydes, ketones, imines and alkynes. Possessing Li–Al cooperativity, ate catalysts are found to be generally superior. Catalytic activity is also influenced by the ligand set, alkyl and/or amido. Devoid of an Al?H bond, iBu₂Al(TMP) operates as a masked hydride reducing benzophenone through a β‐Η transfer process. This catalyst library therefore provides an entry point into the future design of Al catalysts targeting substrate specific transformations.     

Chemoselective Alternating Copolymerization of Limonene Dioxide and Carbon Dioxide: A New Highly Functional Aliphatic Epoxy Polycarbonate

The alternating copolymerization of biorenewable limonene dioxide with carbon dioxide (CO₂) catalyzed by a zinc β‐diiminate complex is reported. The chemoselective reaction results in linear amorphous polycarbonates that carry pendent methyloxiranes and exhibit glass transition temperatures (T_g) up to 135 °C. These polycarbonates can be efficiently modified by thiols or carboxylic acids in combination with lithium hydroxide or tetrabutylphosphonium bromide as catalysts, respectively, without destruction of the main chain. Moreover, polycarbonates bearing pendent cyclic carbonates can be quantitatively prepared by CO₂ insertion catalyzed by lithium bromide.     

A strategy of tailoring stable electrolyte material for high performance proton-conducting solid oxide fuel cells (SOFCs)

A facile strategy was proposed to synthesize Nb-containing BaCeO₃-based material, which is a potential electrolyte for proton-conducting solid oxide fuel cells (SOFCs), via a wet chemical route while the conventional synthesis of Nb-containing oxides relied on the solid state reaction method due to the unavailability of suitable Nb-precursors such as Nb-nitrates resulting in a less desirable fuel cell performance when used as an electrolyte. The BaCe_0.7Nb_0.1Y_0.2O_3 − δ (BCNY) electrolyte material in this study persisted a good chemical stability against CO₂ and exhibited good performance in the fuel cell application. The fuel cell with BCNY electrolyte film showed a high performance of 533 mW cm^− 2 at 700 °C. This cell performance based on BCNY electrolyte was superior to that of many stable modified BaCeO₃-based proton-conducting SOFCs where the electrolytes were tailored by other strategies. This result indicated that the strategy presented in this study could be an effective way to prepare a stable electrolyte for high performance proton-conducting SOFCs, which could advance the development of proton-conducting SOFCs.     

Ammonia Oxidation over Conventional Combustion Catalysts

The combustion of ammonia in air over different conventional oxidation catalysts has been studied in the present work. The final oxidation product is NO, although N₂O is also formed at intermediate temperatures. The environmentally desirable product, N₂, is only appreciably yielded over iron oxides catalysts.     

Submicronic particles of manganese carbonate prepared in reverse micelles: A new electrode material for lithium-ion batteries

A new preparation procedure based on the use of reverse micelles is used in the synthesis of manganese carbonate. A novel monodispersed form of MnCO₃ is obtained, in which particles with a regular shape and ca. 200 nm edges are observed by electron microscopy. The thermal decomposition at 400 °C of this solid under argon leads to the formation of MnO submicron particles. As-prepared MnCO₃ and the product of calcination, MnO, were tested in lithium cells. The electrochemical reaction with lithium of the new MnCO₃ material takes place by a different conversion reaction than the corresponding oxide. The low molecular-weight of MnCO₃ does not penalize the capacity while giving extra stability due to the formation of lithium carbonate as the main side product, which yields better capacity retention. In contrast to other anodes in recent commercial Li-ion product, the use of MnCO₃ submicron particles avoids the presence of the more toxic and expensive cobalt in the stoichiometry of the active electrode material.     

Developments in Titanium-Based Alkali and Alkaline Earth Metal Oxide Catalysts for Sustainable Biodiesel Production: A Review

Biodiesel represents a biodegradable, environmentally friendly, and renewable alternative to fossil fuels. Despite more than three decades of research, significant obstacles still hinder the widespread production of biodiesel. This current review elucidates both the potential and the existing challenges associated with homogeneous and heterogeneous catalysts in catalyzing biodiesel production, with a particular focus on alkali analogues, alkaline earth metal oxides, and titania-based catalysts. In particular, a comprehensive analysis is presented concerning alkali and alkaline earth-based titania (TiO₂) catalysts. Among these, the alkaline earth metal oxides, including lithium, calcium, and strontium when combined with titanium-based catalysts, exhibit superior catalytic activity compared to other metal oxides, owing to their heightened basicity. Consequently, this review offers a thorough and up-to-date insight into the potential of titania-based heterogeneous catalysts for advancing biodiesel production.     

Tuning product selectivity in CO2 hydrogenation over metal-based catalysts

Conversion of CO₂ into chemicals is a promising strategy for CO₂ utilization, but its intricate transformation pathways and insufficient product selectivity still pose challenges. Exploiting new catalysts for tuning product selectivity in CO₂ hydrogenation is important to improve the viability of this technology, where reverse water-gas shift (RWGS) and methanation as competitive reactions play key roles in controlling product selectivity in CO₂ hydrogenation. So far, a series of metal-based catalysts with adjustable strong metal–support interactions, metal surface structure, and local environment of active sites have been developed, significantly tuning the product selectivity in CO₂ hydrogenation. Herein, we describe the recent advances in the fundamental understanding of the two reactions in CO₂ hydrogenation, in terms of emerging new catalysts which regulate the catalytic structure and switch reaction pathways, where the strong metal–support interactions, metal surface structure, and local environment of the active sites are particularly discussed. They are expected to enable efficient catalyst design for minimizing the deep hydrogenation and controlling the reaction towards the RWGS reaction. Finally, the potential utilization of these strategies for improving the performance of industrial catalysts is examined.

A series of metal oxide, phosphate, alloy, and carbide-based catalysts for selective CO₂ hydrogenation are summarized, showing their abilities to switch CO₂ methanation to RWGS.     

n-Octane reforming over modified catalysts: effect of regeneration on the catalyst performance

The effect of multiple oxidation-reduction cycles on the catalyst performance was studied. Pt-Sn-Sn, Pt-Sn-Ir, Pt-Sn-Au and Pt-Sn-Pd supported on g-Al₂O₃ were compared with the reference Pt-Sn/-Al₂O₃ catalyst in n-octane test reactions. The carbonaceous deposits were burned off from the catalysts after each reaction. The regeneration procedure consisted only two steps: the burn off in air and the reduction in hydrogen. No significant change, as a consequence of the regeneration, was observed in the conversion, the liquid yield and the product distribution, except at the Pt-Sn-Pd and Pt-Sn-Au catalysts. These catalysts lost part of their activity. With the palladium modified catalyst the rupture reactions became more dominant with the number of regeneration cycles. The aromatic part of the product decreased, the isoparaffin part increased in the case of both modified catalysts. The reference, the tin and iridium modified catalysts had stable catalytic performance: the activity and selectivity of the catalysts remained constant after a few oxidation cycles.     

Threo-selective aldol condensations of lithium enolates in the presence of trialkylboranes

The reaction of preformed lithium enolates in the presence of trialkylboranes, such as Et₂B and n-Bu₃B, with aldehydes leads to product mixtures rich in the more stable threo aldol.     

Intercalated Iridium Diselenide Electrocatalysts for Efficient pH‐Universal Water Splitting

Developing bifunctional catalysts for both hydrogen and oxygen evolution reactions is a promising approach to the practical implementation of electrocatalytic water splitting. However, most of the reported bifunctional catalysts are only applicable to alkaline electrolyzer, although a few are effective in acidic or neutral media that appeals more to industrial applications. Here, a lithium‐intercalated iridium diselenide (Li‐IrSe₂) is developed that outperformed other reported catalysts toward overall water splitting in both acidic and neutral environments. Li intercalation activated the inert pristine IrSe₂ via bringing high porosities and abundant Se vacancies for efficient hydrogen and oxygen evolution reactions. When Li‐IrSe₂ was assembled into two‐electrode electrolyzers for overall water splitting, the cell voltages at 10 mA cm^?2 were 1.44 and 1.50 V under pH 0 and 7, respectively, being record‐low values in both conditions.     

In situ analysis of interfacial reactions between negative MCMB,lithium electrodes,and gel polymer electrolyte

The interfacial properties of mesocarbon-microbeads (MCMB) and lithium electrodes during charge process in poly (vinylidenefluoride-co-hexafluoropropylene)-based gel electrolyte were investigated by in situ Raman microscopy, in situ Fourier transform-infrared (FTIR) spectroscopic methods, and charge–discharge, electrochemical impedance spectroscopy techniques. For MCMB electrode, the series phase transitions from initial formation of the dilute stage 1 graphite intercalation compound (GIC) to a stage 4 GIC, then through a stage 3 to stage 2, and finally to stage 1 GIC was proved by in situ Raman spectroscopic measurement. The formation of solid electrolyte interface (SEI) films formed on MCMB and metal lithium electrode was studied by in situ reflectance FTIR spectroscopic method. At MCMB electrode surface, the solvent (mostly ethylene carbonate) decomposed during charging process and ROCO₂Li may be the product. ROCO₂Li, ROLi, and Li₂CO₃ were the main composites of SEI film formed on lithium electrode, not on electrodeposited lithium electrode or lithium foil electrode.     

Dearomatization, cetane improvement and deep desulfurization of diesel feedstock in a single-stage reactor

Hydrotreating of light cycle oil over CoMo/Al₂O₃, NiMo/Al₂O₃ and NiW/Al₂O₃ catalysts has shown that the type of catalyst has a critical influence on the composition and properties of the product. Divergent effects of aromatics content and molecular weight on the cetane index by these catalysts occurred. Data show that it was not possible to obtain a diesel product that meets stringent specifications using one type of catalyst in a single-stage reactor even under severe operating conditions.     

Superior Rechargeability and Efficiency of Lithium–Oxygen Batteries: Hierarchical Air Electrode Architecture Combined with a Soluble Catalyst

The lithium–oxygen battery has the potential to deliver extremely high energy densities; however, the practical use of Li‐O₂ batteries has been restricted because of their poor cyclability and low energy efficiency. In this work, we report a novel Li‐O₂ battery with high reversibility and good energy efficiency using a soluble catalyst combined with a hierarchical nanoporous air electrode. Through the porous three‐dimensional network of the air electrode, not only lithium ions and oxygen but also soluble catalysts can be rapidly transported, enabling ultra‐efficient electrode reactions and significantly enhanced catalytic activity. The novel Li‐O₂ battery, combining an ideal air electrode and a soluble catalyst, can deliver a high reversible capacity (1000 mAh g^?1) up to 900 cycles with reduced polarization (about 0.25 V).     

Surface-initiated group transfer polymerization mediated by rare earth metal catalysts

We present the first example of a surface-initiated group transfer polymerization (SI-GTP) mediated by rare earth metal catalysts for polymer brush synthesis. The experimentally facile method allows rapid grafting of polymer brushes with a thickness of >150 nm in <5 min at room temperature. We show the preparation of common poly(methacrylate) brushes and demonstrate that SI-GTP is a versatile route for the preparation of novel polymer brushes. The method gives access to both thermoresponsive and proton-conducting brush layers.