Sites Of Catalysts Research Articles

Tailoring Oxygen Electrocatalytic Performance via Construction of Iron‐Cobalt Oxides and FeN4 Sites on Hierarchical Carbon Fibers for Efficient Zinc–Air Batteries

AbstractThe design and fabrication of non‐precious metal materials for bifunctional oxygen electrocatalytic properties with reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been a research hotspot in the field of zinc–air batteries. Herein, a hierarchical carbon nanofiber immobilized with iron cobalt oxide particles (FeCoOx) and Fe‐Nx sites catalyst is synthesized through electrostatic spinning and the in situ polymerization of pyrrole coupled with pyrolysis. The FeCoOx/Fe─N─C demonstrates a superior bifunctional electrocatalytic performance (E1/2 = 0.91 V, η10 = 350 mV). Liquid zinc–air batteries employing FeCoOx/Fe─N─C exhibit a high power of 184.8 mW cm−2 and more than 580 cycles of stable cycling ability. Additionally, the incorporation of iron cobaltite introduces extra electrons and optimizes the adsorption capacity for oxygen intermediates, effectively boosting the inherent ORR activity. The experimental results illustrate that the special geometrical structure of spinel ferrite provides excellent OER catalytic performance. Theoretical calculations indicate that the incorporation of FeCoOx shifts the d‐band center of iron closer to the Fermi level (Ef), thereby modulating the hybridization between Fe 3d and O 2p orbitals. This work offers an effective approach to constructing coupling catalysts that have single atoms coexisting with oxide particles for efficient bifunctional catalysis.

Electron Transfer Energetics in Photoelectrochemical CO2 Reduction at Viologen Redox Polymer-Modified p-Si Electrodes.

While redox polymer-mediated catalysis at silicon photoelectrodes has been studied since the 1980s, there have been few detailed studies of these materials in photoelectrochemical CO2 reduction. Here, we develop silicon photoelectrodes functionalized with a viologen-based polymer that mediates the formation of catalytic gold nanoparticles. The presence of gold was confirmed by X-ray photoelectron spectroscopy (XPS), and the nanoparticles were imaged with high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). We probed the CO2 reduction process during bulk photoelectrolysis to find modest, yet consistent CO faradaic efficiencies across a range of applied potentials. Operando surface-enhanced Raman spectroscopy (SERS) was used to measure the Fermi levels of both the viologen polymer and the Au catalyst sites. The operando measurement of the Fermi levels of all three components of the photocathode provides a unified picture of the electron transfer process in the semiconductor-redox polymer-catalyst system. The redox polymer serves as the electron transfer mediator between the Si substrate and Au sites. In addition, the Au Fermi level equilibrates with the Fermi level of the viologen polymer, which in turn fixes the quasi-Fermi level of Au catalysts at the p-Si/redox polymer interface. This suggests a potential future direction of using redox polymers with tunable potentials to modulate the potential of metal cocatalysts and thus control the reaction selectivity.

Quantitative Basicity‐Activity Correlation in Ru‐Imidazolium Ionic Liquid‐Catalyzed Acetylene Hydrochlorination

AbstractIonic liquids (ILs), as liquid‐phase media in acetylene hydrochlorination, not only optimize the mixing environment of reactants but also stabilize the active sites of metal catalysts. Nevertheless, research in this field is still in its early stages, and systematic analysis and in‐depth study of liquid‐phase media‐ionic liquids are still insufficient. In this study, imidazolium‐based ILs ([Bmim]X) with different hydrogen bond basicity (β) values were used to fine‐tune the Ru‐based liquid‐phase catalytic system (Ru‐[Bmim]X). It was found that as the β value of [Bmim]X increased, its solubility in HCl and C2H2 also increased, resulting in a volcanic trend in the activity of the Ru‐[Bmim]X catalysts. Through systematic characterization and theoretical calculations, we identified the active site of the Ru‐[Bmim]Cl catalyst as the [RuCl4]− anion and confirmed that the reaction is a two‐step mechanism. Various anions of [Bmim]X influence the adsorption of reactants and reactive energy barriers by modulating the electronic and steric effects at the active sites. In particular, the Ru‐[Bmim]Cl catalyst showed a remarkable conversion rate of 86.8% and high stability even at a low temperature of 110 °C. These results provide the scientific basis for the development of novel and efficient liquid‐phase catalytic systems.

Co Single-Atom Catalysis for High-Efficiency LiCl/Cl2 Conversion in Rechargeable Lithium-Chlorine Batteries.

Lithium-chlorine (Li-Cl2) secondary batteries are emerging as promising candidates for high-energy-density power sources and an extensive operational temperature range. However, conventional electrode materials suffer from weak adsorption forchlorine gas (Cl2) and low conversion efficiency of lithium chloride (LiCl), leading to significant loss of chlorine-based active materials. This issue hampers the cyclability of Li-Cl2 batteries. In this work, it is demonstrated that synergistic Cl2 adsorption on the electrode surface and the energy barrier for LiCl reactions are crucial for enhancing Cl2/LiCl conversion efficiency. Consequently, a cobalt (Co) single-atom site catalyst with a Co-N4 coordination environment has been developed, which significantly diminishes the transformation barrier of solid LiCl particles into Cl2 and concurrently enhances the chemical adsorption of Cl2, facilitating uniform nucleation of LiCl. As a result, the Li-Cl2@Co-NC battery developed has achieved a 0.6V reduction in polarization voltage under high current densities, effectively addressing the issue of low conversion efficiency between Cl2 and LiCl. At room temperature, the Li-Cl2@Co-NC battery achieves over 600 cycles at 1500mAg-1; At -40°C, it reaches 650 cycles at 500mAg-1. The research overcomes the cycle stability barrier in high-current Li-Cl2 batteries and offers a strategy for batteries with a wide temperature range and long cycle life.

Enhanced Alkaline Water Electrolysis by the Rational Decoration of RuOx with the In Situ-Grown CoFe Nanolayer.

Rational engineering of the surfaces of heterogeneous catalysts (especially the surfaces of supported metals) can endow intriguing catalytic functionalities for electrochemical reactions. However, it often requires complicated steps, and even if it does not, breaking the trade-off between activity and stability is quite challenging. Herein, we present a strategy for reconstructing supported catalysts via in situ growth of metallic nanolayers from the perovskite oxide support. When Ru-coated LaFe0.9Co0.1O3 is thermally reduced, the CoFe nanoalloy spontaneously migrates onto the Ru and greatly increases the physicochemical stability of Ru in alkaline water electrolysis. Benefiting from an 81% reduction in Ru dissolution after decoration, it operates for over 200 h without noticeable degradation. Furthermore, the underlying Ru modifies the electronic structure and surface adsorption properties of the CoFe overlayer toward reaction intermediates, synergistically catalyzing both the oxygen evolution reaction and the hydrogen evolution reaction. Specifically, the mass activity of the oxygen evolution reaction is 64.1 times greater than that of commercial RuO2. Our work highlights a way to protect inherently unstable Ru from dissolution while allowing it to influence surface kinetics from the subsurface sites in heterogeneous catalysts.

The Jahn-Teller Effect: A Significant Influence on Single-atom Sites Catalysts for CO2 Photoreduction.

The pursuit of efficient photocatalytic materials has gained momentum because of increasing concerns over climate change and the urgent need for sustainable energy solutions. The Jahn-Teller effect is a fundamental phenomenon prevalent in metal complexes and exerts a significant influence on the design and performance of catalytic systems. It affects the redistribution of d-orbital electrons, thus impacting electron transfer efficiency, the stability of reaction intermediates, and the adsorption energies of reactants, ultimately resulting in enhanced catalytic efficiency. This concept systematically discusses the mechanisms underlying the Jahn-Teller effect and its implications for catalytic activity, with a particular emphasis on photocatalytic CO2 reduction. We discuss various strategies aimed at optimizing the stability and activity of single-atom site catalysts through the rational exploitation of Jahn-Teller twisting effects. Furthermore, we highlight recent advancements in this field and propose future research directions, underscoring the potential of engineered Jahn-Teller sites to significantly enhance the efficiency of photocatalytic CO2 reduction.

High-dispersion/N-doping FeCo@NC with abundant active sites for high-activity oxygen reduction catalysts

High-dispersion/N-doping FeCo@NC with abundant active sites for high-activity oxygen reduction catalysts

Boosting PMS Activation Through Fe3S4/WO3: The Essential Impact of WX and SX on Catalyst Activity and Regeneration Fe Active Sites for Efficient Pollutant Removal

Fe-based heterogeneous catalytic advanced oxidation processes show great potential for treating wastewater. However, catalyst instability often hinders their practical use, mainly due to the slow regeneration of Fe2+ sites. Herein, we developed a Fe3S4/WO3 catalyst, where the electron-rich Wx and Sx sites promoted efficient electron transfer, enabling continuous regeneration of Fe2+ active sites on the catalyst surface. The Fe3S4/WO3 catalyst exhibited outstanding degradation efficiency for tetracycline (TC) in the peroxymonosulfate (PMS) system, achieving a 92.5% removal efficiency, significantly higher than its individual components of Fe3S4 (52.8%), WO3 (43.1%), and WS2 (53.2%). Moreover, the Fe3S4/WO3/PMS system demonstrated a broad operational pH range (3.0–9.0), excellent degradation efficiency for various emerging pollutants, minimal interference from background electrolytes and organic matter, and strong stability in real water treatment. Chemical scavenger tests and electron paramagnetic resonance (EPR) analysis confirmed that the oxidative degradation of TC was driven by multiple reactive species, including SO4•−, •OH, •O2−, and 1O2. This study provides a novel strategy for regulating active sites in Fe-based catalysts to ensure sustained performance, offering a pathway for the rational design of next-generation Fenton-like catalysts for efficient and sustainable micropollutant removal from wastewater.

Photo‐ / photothermal‐ / electro‐driven catalytic CO2 conversion into dimethyl carbonate

Dimethyl carbonate (DMC), an important and environmentally friendly chemical intermediate, has found widespread application in various industrial processes. In this review, we summarize the recent progress in the photo‐ / photothermal‐ / electro‐fixing of CO2 into DMC, focusing on the mechanisms of electron transfer, multi‐step chemical reaction pathways, and the design active sites of catalysts. This review highlights the characteristics and advantages of photothermal catalysis in the conversion of CO₂ to DMC by comparing the challenges posed by the high energy consumption required for thermocatalytic processes under high‐pressure conditions and the limited efficiency of photocatalysis. Advances in photothermal catalysis are discussed, particularly focusing on metal‐semiconductor composites and defect engineering strategies. Furthermore, this review systematically addresses the structure‐activity relationships of catalysts for the direct synthesis of DMC from CO2 and methanol, leveraging in situ characterization techniques and density functional theory (DFT). Finally, future challenges and potential opportunities for enhancing CO2 utilization via DMC production are outlined, emphasizing the significance of these advancements for sustainable chemical processes.

Light Enhanced Water Dissociation in Bipolar Membranes

AbstractBipolar membrane (BPM) integration can allow robust and abundant materials to be implemented into energy conversion frameworks and purification pathways vital for the development of clean technologies. However, large membrane voltages associated with water dissociation (WD) have hampered widespread adoption. This work investigates an alternative method to reduce the overvoltage associated with WD operation by illuminating the BPM interface in the presence of nanoparticulate catalyst layers that exhibit plasmonic character. The plasmonic character of the catalyst enhanced the field locally near the active catalyst site, lowering the resistance associated with WD as well as the onset potential for WD. Optimal catalyst loadings allowed a balance of light absorption, catalyst activity, and field utilization. Composites of known WD catalysts that exhibited minimal light activity with a plasmonic and WD active material exhibited improvements in the WD resistance and overvoltage of up to 20 % upon irradiation. This proof‐of‐concept work introduces a new paradigm for altering WD activity in BPMs, where the optical activity of WD catalysts can provide further tunability towards efficient WD and alternative energy conversion frameworks.

Identification and Quantification of Al Pairs and Their Impact on Dealumination in Zeolites.

Understanding the precise quantity and spatial distribution of paired aluminum (Al) sites in zeolite catalysts is crucial, as they significantly impact the catalytic performance via synergistic effects and long-term stability. In this study, a novel strategy by employing divalent cation titration with varying cation sizes, in combination with advanced quantitative 1H NMR and 1H-1H homonuclear correlation techniques, has been developed to accurately identify and classify three distinct types of Al pairs. These include two types of Al pairs aligned along six-membered rings (6-MRs) and 10-membered rings (10-MRs), the latter of which are essentially composed of Al atoms located in different 6-MR or 5-MR. The third type comprises two Al atoms located in different channels. The second and third types had been challenging to probe in the past, yet they may be critical for catalysis, particularly the second type demonstrating proximity close enough to accommodate Ba2+ (with a radius of 1.49 Å). Our strategy for quantifying each type of Al pair marks a significant advancement in the understanding of the zeolite framework. Furthermore, controlled hydrothermal treatments using stepwise steaming reveal that a higher concentration of Al pairs accelerates dealumination, primarily for dynamic reasons of water molecules but not intrinsic structural instability induced by Al pairs. To address this, we propose a "bi-Al" vs "mono-Al" hydrolysis model, offering fresh insights into the pivotal role of Al pairs on zeolite stability. This work opens new avenues for optimizing zeolite-based catalysts for enhanced performance and longevity.

Exploring the properties, types, and performance of atomic site catalysts in electrochemical hydrogen evolution reactions.

Atomic site catalysts (ASCs) have recently gained prominence for their potential in the electrochemical hydrogen evolution reaction (HER) due to their exceptional activity, selectivity, and stability. ASCs with individual atoms dispersed on a support material, offer expanded surface areas and increased mass efficiency. This is because each atom in these catalysts serves as an active site, which enhances their catalytic activity. This review is focused on providing a detailed analysis of ASCs in the context of the HER. It will delve into their properties, types, and performance to provide a comprehensive understanding of their role in electrochemical HER processes. The introduction part underscores HER's significance in transitioning to sustainable energy sources and emphasizes the need for innovative catalysts like ASCs. The fundamentals of the HER section emphasizes the importance of understanding the HER and highlights the key role that catalysts play in HER. The review also explores the properties of ASCs with a specific emphasis on their atomic structure and categorizes the types based on their composition and structure. Within each category of ASCs, the review discusses their potential as catalysts for the HER. The performance section focuses on a thorough evaluation of ASCs in terms of their activity, selectivity, and stability in HER. The performance section assesses ASCs in terms of activity, selectivity, and stability, delving into reaction mechanisms via experimental and theoretical approaches, including density functional theory (DFT) studies. The review concludes by addressing ASC-related challenges in HER and proposing future research directions, aiming to inspire further innovation in sustainable catalysts for electrochemical HER.

Engineering the Lewis Acidity of Fe Single-Atom Sites via Atomic-Level Tuning of Spatial Coordination Configuration for Enhanced Oxygen Reduction.

Nitrogen-doped carbon-supported Fe catalysts (Fe-N-C) with Fe-N4 active sites hold great promise for the oxygen reduction reaction (ORR). However, fine-tuning the structure of Fe-N4 active sites to enhance their performance remains a grand challenge. Herein, we report an innovative design strategy to promote the ORR activity and kinetics of Fe-N4 sites by engineering their Lewis acidity, which is achieved by tuning the spatial Fe coordination geometry. Theoretical calculations indicated that Fe1-N4SO2 sites (with an axial -SO2 group bonded to Fe) offered favorable Lewis acidity for the ORR, leading to optimized adsorption energies for the key ORR intermediates. To implement this strategy, we developed a molecular-cage-encapsulated coordination strategy to synthesize a Fe single-atom site catalyst (SAC) with Fe1-N4SO2 sites. In agreement with theory, the Fe1-N4SO2/NC catalyst demonstrated outstanding ORR performance in both alkaline (E1/2 = 0.910 V in 0.1 M KOH) and acidic media (E1/2 = 0.772 V in 0.1 M HClO4), surpassing commercial Pt/C and traditional Fe SACs with Fe1-N4 sites or planar S-coordinated Fe1-N4-S sites. Moreover, this newly developed catalyst showed great application potential in quasi-solid-state Zn-air batteries, delivering superior performance across a wide temperature range.

Planar chlorination engineering induced symmetry-broken single-atom site catalyst for enhanced CO2 electroreduction

Breaking the geometric symmetry of traditional metal-N4 sites and further boosting catalytic activity are significant but challenging. Herein, planar chlorination engineering is proposed for successfully converting the traditional Zn-N4 site with low activity and selectivity for CO2 reduction reaction (CO2RR) into highly active Zn-N3 site with broken symmetry. The optimal catalyst Zn-SA/CNCl-1000 displays a highest faradaic efficiency for CO (FECO) around 97 ± 3% and good stability during 50 h test at high current density of 200 mA/cm2 in zero-gap membrane electrode assembly (MEA) electrolyzer, with promising application in industrial catalysis. At -0.93 V vs. RHE, the partial current density of CO (JCO) and the turnover frequency (TOF) value catalyzed by Zn-SA/CNCl-1000 are 271.7 ± 1.4 mA/cm2 and 29325 ± 151 h-1, as high as 29 times and 83 times those of Zn-SA/CN-1000 without planar chlorination engineering. The in-situ extended X-ray absorption fine structure (EXAFS) measurements and density functional theory (DFT) calculation reveal the adjacent C-Cl bond induces the self-reconstruction of Zn-N4 site into the highly active Zn-N3 sites with broken symmetry, strengthening the adsorption of *COOH intermediate, and thus remarkably improving CO2RR activity.

Accelerated Design of Dual-Metal-Site Catalysts via Machine-Learning Prediction.

Dual-metal site catalysts (DMSCs) supported on nitrogen-doped graphene have shown great potential in heterogeneous catalysis due to their unique properties and enhanced efficiency. However, the precise control and stabilization of metal dimers, particularly in oxygen activation reactions, present significant challenges in practical applications. In this study, we integrate high-throughput density functional theory calculations with machine learning techniques to predict and optimize the catalytic properties of DMSCs. Transfer learning is employed to enhance the model's generalization capability, successfully predicting catalytic performance across new metal combinations. Additionally, the application of the SISSO method enables the derivation of interpretable symbolic regression models, revealing critical correlations between electronic structure features and catalytic efficiency. This approach not only advances the understanding of dual-metal site catalysis but also provides a novel framework for the systematic design and optimization of highly efficient catalysts, with broad applicability in catalytic science.

Electrochemical Scanning Microwave Microscopy Reveals Ion Intercalation Dynamics and Maps Active Sites in 2D Catalyst.

The accelerated demand for electrochemical energy storage urges the need for new, sustainable, and lightweight materials able to store high energy densities rapidly and efficiently. Development of these functional materials requires specialized techniques that can provide a close insight into the electrochemical properties at the nanoscale. For this reason, the electrochemical scanning microwave microscopy (EC-SMM) enabling local measurement of electrochemical properties with nanometer spatial resolution and sensitivity down to atto-Ampere electrochemical currents is introduced. Its power is demonstrated by studying NiCo-layered double hydroxide flakes, revealing active site locations and providing atomistic insights into the catalytic process. EC-SMM's spatial resolution of 16 ±1nm allows detailed analysis of edge effects in this 2D material, including localized electrochemical impedance spectroscopy and cyclic voltammetry. Coupled with advanced numerical modeling of diffusion and migration dynamics at the material interface, the findings elucidate the previously hypothesized processes responsible for localized enhancements in electrochemical activity, while pinpointing essential parameters for tuning the thermodynamics of ion intercalation and optimizing surface adsorption.

Tuning surface-active sites of Ru catalysts for the selective deoxygenation of lignin monomers to fuels and chemicals

Tuning surface-active sites of Ru catalysts for the selective deoxygenation of lignin monomers to fuels and chemicals

Improving Electrocatalytic CO2 Reduction over Iron Tetraphenylporphyrin with Triethanolamine as a CO2 Shuttle.

Delivering CO2 molecules to catalyst sites is a vital step in the CO2 reduction reaction (CO2RR). Achievements have been made to develop efficient catalysts, but few efforts have been dedicated to improving CO2 delivering in solutions. Herein, we report on electrocatalytic CO2-to-CO conversion using Fe tetraphenylporphyrin (FeTPP) as a catalyst and triethanolamine as a CO2 shuttle. Compared to ethanol, the electrocatalytic CO2RR current with triethanolamine increases by more than three times. We show that triethanolamine can effectively capture a CO2 molecule to form a zwitterionic alkylcarbonate through the collaboration between its tripodal alcohol and amine units. This alkylcarbonate can release the bound CO2 molecule for activation at the Fe site upon its interaction with FeTPP. In addition to shuttling CO2, alkylcarbonates can also provide protons to assist the C-O bond cleavage. Therefore, this work is significant to demonstrate a new strategy to improve electrocatalytic CO2RR by shuttling CO2.

Fundamentals and Perspectives of Positively Charged Single-Metal Site Catalysts for CO2 Electroreduction.

Single-atom catalysts (SACs) show superior efficiency in electrocatalytic carbon dioxide reduction, a key stage in achieving carbon neutrality. Atomically dispersed single-metal sites of SACs are invariably in a positive valence state; namely, they are positively charged single-metal sites (PCSSs). The PCSS catalysts generally possess a distinctive and asymmetric electronic structure, which enables the activation of linear carbon dioxide molecules and stabilizes miscellaneous intermediates during electrocatalysis. Herein, this review summarizes the manner in which the coordination environment, neighboring atoms or groups, and the interaction with the substrate modulate the distinctive electronic properties of PCSSs. Additionally, we overview the recently reported theoretical and experimental advances in terms of structure-performance relationship. Furthermore, we emphasize the previously underappreciated durability of positively charged single-metal sites in CO2 reduction. Finally, we discuss several pending issues and potential breakthroughs of PCSSs for CO2 reduction.

Regulating the electronic structure of iron sites in single-atom catalyst with interfacial chemical bond to enhance Fenton-like reaction.

Regulating the electronic structure of iron sites in single-atom catalyst with interfacial chemical bond to enhance Fenton-like reaction.