EES catalysis最新文献

Exploring the dynamic interaction of non-thermal plasma (NTP) with catalytic processes is critical to unravelling elusive catalyst structure–function relationships under NTP conditions, specifically dielectric barrier discharges (DBD). This study investigates the efficacy of operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) as a tool for characterizing intermediates created by NTP on catalyst surfaces. Leveraging insights from traditional DRIFTS in thermochemical catalysis, we explore the complexities of plasma-induced catalytic reactions, discussing both opportunities and limitations of DRIFTS to study these reaction mechanisms. By summarizing findings from literature and addressing existing knowledge gaps, this perspective highlights how different DRIFTS configurations can affect results, stressing the importance of establishing best practices for studying DBD-driven reactions with DRIFTS. The intended outcomes of this work are to provide guidance on how to effectively use DRIFTS, share fundamental insights into DBD-assisted catalysis, and emphasize the need for complementary techniques to develop catalysts suited for NTP environments.

We would like to take this opportunity to thank all of EES Catalysis's reviewers for helping to preserve quality and integrity in chemical science literature. We would also like to highlight the Outstanding Reviewers for EES Catalysis in 2023.

The photocatalytic non-oxidative coupling of methane (NOCM) is a highly challenging and sustainable reaction to produce H₂ and C₂₊ hydrocarbons under ambient conditions using sunlight. However, there is a lack of knowledge, particularly on how to achieve high photocatalytic yield in continuous-flow reactors. To address this, we have developed a novel flow-through photocatalytic reactor for NOCM as an alternative to the conventionally used batch reactors. Me/TiO₂ photocatalysts, where Me = Au, Ag and Pd, are developed, but only those based on Pd are active. Interestingly, the preparation method significantly impacts performance, going from inactive samples (prepared by wet impregnation) to highly active samples (prepared by strong electrostatic adsorption – SEA). These photocatalysts are deposited on a nanomembrane, and the loading effect, which determines productivity, selectivity, and stability, is also analysed. Transient absorption spectroscopy (TAS) analysis reveals the involvement of holes and photoelectrons after charge separation on Pd/TiO₂ (SEA) and their interaction with methane in ethane formation, reaching a production rate of about 1000 μmol g⁻¹ h⁻¹ and a selectivity of almost 95% after 5 hours of reaction. Stability tests involving 24 h of continuous irradiation are performed, showing changes in productivity and selectivity to ethane, ethylene and CO₂. The effect of a mild oxidative treatment (80 °C) to extend the catalyst's lifetime is also reported.

The development of unified regenerative fuel cells (URFCs) necessitates an active and stable bifunctional oxygen electrocatalyst. The unique challenge of possessing high activity for both the oxygen reduction (ORR) and oxygen evolution (OER) reactions, while maintaining stability over a wide potential window impedes the design of bifunctional oxygen electrocatalysts. Herein, two design strategies are explored to optimize their performance. The first incorporates active sites for the ORR and OER, Mn and Co, into a single perovskite structure, which is achieved with the perovskites Ba_0.5Sr_0.5Co_0.8Mn_0.2O_3−δ (BSCM) and La_0.5Ba_0.25Sr_0.25Co_0.5Mn_0.5O_3−δ (LBSCM). The second combines an active ORR perovskite catalyst (La_0.4Sr_0.6MnO_3−δ (LSM)) with an OER active perovskite catalyst (Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF)) in a physical mixed composite (BSCF/LSM). The success of the two strategies is investigated by measuring the catalysts’ catalytic performance and response to alternating reducing and oxidizing potentials to mimic the dynamic conditions experienced during the operation of URFCs. Additionally, the continuous, potentiodynamic change in Mn, Co, and Fe oxidation states during the ORR and OER is elucidated with operando X-ray absorption spectroscopy (XAS) measurements, revealing key insights into the nature of the active sites. The results reveal important catalyst physiochemical properties and provide a guide for future research and design principles for bifunctional oxygen electrocatalysts.

The design and development of supported catalysts for the oxygen evolution reaction (OER) is a promising pathway to reducing iridium loading in proton exchange membrane water electrolysers. However, supported catalysts often suffer from poor activity and durability, particularly when deployed in membrane electrode assemblies. In this work, we deploy iridium coated hollow titanium dioxide particles as OER catalysts to achieve higher Ir mass activities than the leading commercial catalysts. Critically, we demonstrate state-of-the-art durabilities for supported iridium catalysts when compared against the previously reported values for analogous device architectures, operating conditions and accelerated stress test profiles. Through extensive materials characterisations alongside rotating disk electrode measurements, we investigate the role of conductivity, morphology, oxidation state and crystallinity on the OER electrochemical performance. Our work highlights a new supported catalyst design that unlocks high-performance OER activity and durability in commercially relevant testing configurations.

Hydrogen production of seawater electrolysis has attracted considerable interest due to the abundant seawater resources. However, the chloride ions (Cl⁻) in seawater not only corrode the electrodes but also cause side reactions, severely impacting the electrode efficiency and stability of the oxygen evolution reaction (OER) in seawater electrolysis. These challenges are the key factors limiting the development of seawater electrolysis technology. Here, we developed a surface-functionalized high-performance catalyst, which not only resists Cl⁻ corrosion using surface-functionalized ions, but also improves the OER activity by surface amorphization. The designed catalyst (Ru_0.1-NiFeOOH/PO₄³⁻) is composed of Ru_0.1-NiFeOOH and surface phosphate. On the one hand, a small amount of Ru doping can increase the surface amorphization of NiFeOOH and thus improve the catalytic activity. On the other hand, the phosphates on Ru_0.1-NiFeOOH are resistant to Cl⁻ corrosion, which in turn improves the electrode stability. This catalyst demonstrates robust performance operation over 1000 h in alkaline seawater solutions at an industrial current density of 0.5 A cm⁻². The anion exchange membrane seawater electrolyzer assembled with Ru_0.1-NiFeOOH/PO₄³⁻ only needs 1.6 V to achieve 0.5 A cm⁻² when powered by sustainable solar energy. The electrolyzer efficiency is 75.1% at 0.5 A cm⁻², which is superior to the 2030 technical target of 65% set by the U.S. DOE and most reported work. This work offers a new perspective for designing efficient and stable catalysts and is of great significance for advancing seawater electrolysis technology.

As an extensively used industrial catalyst for oxidation reactions, supported vanadium oxide (VO_x) is a promising candidate for oxidative dehydrogenation of propane with carbon dioxide (CO₂-ODP). Although the structure of VO_x is found to be a key factor in determining the catalytic activity and stability of supported VO_x for CO₂-ODP, the essential reason still remains elusive at the molecular level. To shed some light on this fundamental issue, VO_x/(−)SiO₂ catalysts with narrow distributions of V loading while well-defined structures of VO_x species, i.e., monomeric VO_x, less polymeric VO_x, highly polymeric VO_x and V₂O₅ crystallites, were purposely synthesized by appropriate methods, including one-pot hydrothermal synthesis, incipient wetness impregnation and physical grinding. We found that the catalytic activity and stability of VO_x species decrease in the order of monomeric VO_x > less polymeric VO_x > highly polymeric VO_x > crystalline V₂O₅, which coincides with the ability for the re-oxidation of the correspondingly reduced VO_x species by CO₂. As a result of the most facile re-oxidation of the reduced monomeric VO_x species by CO₂, a well matched redox cycle of V⁵⁺/V⁴⁺ oxides during CO₂-ODP can be maintained with increasing the time on stream, leading to an improved stability of the catalyst with more monomeric VO_x. These mechanistic findings on the redox properties of VO_x with different structures can be guidelines for developing a high-performance VO_x-based catalyst for CO₂-ODP.

We develop a catalytic process comprising exclusively of flow reactions for conversion of wet waste-derived volatile fatty acids to sustainable aviation fuel (SAF) and key aromatic building blocks (benzene, toluene, ethylbenzene, and xylene; BTEX). Acids are upgraded via sequential ketonization and either cyclization of light (C_3–7) ketones to BTEX and an aromatic SAF blendstock or hydrodeoxygenation of C₈₊ ketones to an alkane SAF blendstock. The enabling step investigated in this work is light ketone cyclization over H/ZSM-5, which was chosen through screening upgrading of 4-heptanone over solid acidic and basic catalysts. We then determined the reaction network of 4-heptanone upgrading by analyzing selectivity trends with conversion and concluded that the reaction should be run at full conversion. Finally, we demonstrated the entire acid upgrading process by converting commercial food waste-derived carboxylic acids to SAF blendstocks and BTEX. We blended the C₉₊ aromatic and alkane products to create one SAF blendstock and show that this mixture can be blended 50/50 with Jet A and meet all critical property standards. Techno-economic analysis and life cycle assessment show that utilizing a food waste feedstock for the process can be economically feasible with current policy incentives and reduce greenhouse gas emissions by more than 250%.

Porous aromatic frameworks (PAFs) as visible-light active and reusable photocatalysts provide a green and sustainable alternative to conventional metal-based photocatalysts. In this study, we design and synthesize three novel photoactive tetraphenylethylene (TPE) based PAF photocatalysts (TPE-PAFs) linked with thiophene units in an alternating donor (D)–acceptor (A) fashion. Photoelectrochemical measurements show that the introduction of different thiophene units can effectively regulate the optical band gap and energy level, which may further determine their photocatalytic performance. As a result, TPE-PAFs achieve excellent yields (up to 99%), broad substrate scope and high recyclability (up to 10 cycles) for the photosynthesis of benzimidazoles. The photocatalytic reaction is successfully monitored using in situ IR spectra. This work provides a feasible approach for designing PAFs with high photocatalytic activity and broadens the application of PAFs for photocatalytic organic transformations.

Chemical recycling of polyvinyl chloride (PVC) waste poses challenges due to its high chloride content and varied additive formulations. We present a dual catalytic system enabling full conversion of post-consumer PVC waste via tandem dehydrochlorination–hydrogenation. Using a ZnCl₂ catalyst (0.1–0.2 eq.) for dehydrochlorination and a Ru catalyst (1.0 mol%) for hydrogenation, it directly converts PVC into a lower molecular weight polyethylene (PE)-like polymer. It prevents the problematic formation of polyenes and aromatic char during thermal processing. The system tolerates common additives (e.g. plasticisers and Pb-, Zn- and Ca/Zn-based stabilisers) and effectively dechlorinates materials with high inorganic filler content. The method can process PVC materials with a wide range of M_n values (29 000–120 000 g mol⁻¹). Methyl cyclohexanecarboxylate emerges as a suitable solvent for the tandem reaction, thereby producing 100% dechlorinated products with low molar mass averages (M_n ∼ 2400 g mol⁻¹ and M_w ∼ 5000 g mol⁻¹) and allows additive removal. X-ray absorption spectroscopy (XAS) and a study of the reactivity of a model compound elucidate the Ru-catalyst structure and the chain splitting mechanism. This tandem process yields soluble short-chained polymer fragments, facilitating industrial processing and additive removal from chlorinated plastic waste.