Sites Of Catalysts Research Articles

Refining the Distinct Cu-N4 Coordination in Mesoporous N-Doped Carbon to Boost Selective Deuteration under Mild Conditions.

Deuterated compounds have broad applications across various fields, with dehalogenative deuteration serving as an efficient method to obtain these molecules. However, the diverse electronic structures of active sites in the heterogeneous system and the limited recyclability in the homogeneous system significantly hinder the advancement of dehalogenative deuteration. In this study, we present a catalyst composed of copper single-atom sites anchored within an ordered mesoporous nitrogen-doped carbon matrix, synthesized via a mesopore confinement method. The Cu1/OMNC-1100 catalyst, characterized by Cu-N4 sites, demonstrates exceptional performance, high functional group tolerance, and remarkable durability in the deuteration of 2-bromo-6-methoxynaphthalene under relatively mild conditions (80 °C, 2 MPa of CO). Experimental results combined with X-ray absorption fine structure analysis reveal that Cu-N3 sites can be converted into more stable Cu-N4 counterparts at higher pyrolysis temperatures, resulting in enhanced catalytic activity. This work demonstrates a strategy for designing single-atom site catalysts with tunable coordination environments, providing a promising approach to improving catalytic performance in selective dehalogenative reactions under relatively mild conditions.

Enhancing Photocatalytic CO2RR by Modulating the Active Sites of COF-Based Catalysts.

The catalytic conversion of CO2 into valuable chemicals using metalized covalent organic frameworks (COFs) as catalysts is a promising method for reducing atmospheric CO2 levels. Herein, a aldehyde-amine COF (TAPT-Tp) at room temperature and pressure and their metallized results is synthesized, Ni-TAPT-Tp and Ti-TAPT-Tp. The photocatalytic results indicate that the CO2 to CO reduction rate is 6182.5µmol g-1h-1 for Ni-TAPT-Tp, but only 1615.4µmol g-1h-1 for Ti-TAPT-Tp. Density functional theory (DFT) simulations further demonstrate that for intermediates *CO2, *COOH, and *CO, the energy of Ni-TAPT-Tp is consistently lower than that of Ti-TAPT-Tp, indicating that Ni-TAPT-Tp exhibits superior photocatalytic performance for CO2RR. This work provides a reference for optimizing the coordination structure of M-COFs to obtain highly active and selective CO2RR.

Interfacial Catalysis at Atomic Level.

Heterogeneous catalysts are pivotal to the chemical and energy industries, which are central to a multitude of industrial processes. Large-scale industrial catalytic processes rely on special structures at the nano- or atomic level, where reactions proceed on the so-called active sites of heterogeneous catalysts. The complexity of these catalysts and active sites often lies in the interfacial regions where different components in the catalysts come into contact. Recent advances in synthetic methods, characterization technologies, and reaction kinetics studies have provided atomic-scale insights into these critical interfaces. Achieving atomic precision in interfacial engineering allows for the manipulation of electronic profiles, adsorption patterns, and surface motifs, deepening our understanding of reaction mechanisms at the atomic or molecular level. This mechanistic understanding is indispensable not only for fundamental scientific inquiry but also for the design of the next generation of highly efficient industrial catalysts. This review examines the latest developments in atomic-scale interfacial engineering, covering fundamental concepts, catalyst design, mechanistic insights, and characterization techniques, and shares our perspective on the future trajectory of this dynamic research field.

Selective production of lactitol from lactose using the Lewis acid site of MOF catalysts without exogenous hydrogen

Lactose is found in the residue obtained from the separation of high value-added proteins from whey and can be used to solve the problem of waste generated by the agri-food...

Platinum nanoparticles anchored on Ru-NX doped carbon: Synergistic dual-active site catalysts for oxygen reduction reactions

Platinum nanoparticles anchored on Ru-NX doped carbon: Synergistic dual-active site catalysts for oxygen reduction reactions

Regulating Carbon Vacancies and Undercoordinated Mo Sites in Mo2C Catalysts Toward Photo-Thermal Catalytic Conversion of Biomass Into H2 Fuel.

The conversion of biomass into chemical fuels is exciting but quite challenging in the development of an effective conversion strategy to generate easily-separated products without energy consumption. Herein, a lignocellulosic biomass-to-H2 conversion system via photo-thermal catalysis over Mo2C hierarchical nanotube catalysts in an acidic solution, in which the lignocellulose is hydrolyzed to small organic molecules (such as glucose, etc) by dilute H2SO4, and then the resulting glucose is oxidized by Mo2C catalyst to generate H2 are reported. During the photo-thermal catalytic processes, the carbon vacancy in Mo2C catalysts results in the generation of undercoordinated Mo sites, which act as active sites for both biomass oxidation and H2 generation reactions. Thus, the successful photo-thermal catalytic conversion of common agricultural and forestry biomass including polar wood chip, bamboo, wheat straw, rice straw, corncob, and rice hull into H2 fuel is realized, and the highest H2 generation rate achieves 30 µmolg-1h-1 in the wheat straw system. Outwork affords efficient noble-metal-free catalysts with adjustable active sites for photo-thermal catalytic conversion of lignocellulosic biomass into H2.

FeCu-N6-C Diatomic Sites Catalyst for the Boosted Oxygen Reduction Reactions in Zinc-Air Batteries.

Due to the high catalytic activity and stability for oxygen reduction reaction, N-coordinated Fe-Cu dual-metal doped carbon material (FeCu-N-C) is considered to be one of the promising electrode materials for metal-air battery and fuel cells. Herein, FeCu-N-C dual-metal catalysts was synthesized by an adsorption-calcination strategy. The prepared FeCu-N-C exhibited high activity and stability both in alkaline and acidic media. In alkaline/acid medium, the half-wave potential reaches to 0.90/0.80 V, which is better than Fe-N-C catalyst. The power density for FeCu-N-C in zinc-air battery reaches to 220 mW cm-2 and shows high electrochemical stability for more than 600 hours in charge/discharge cycles, much higher than 130 hours for Pt/C (40 %) and 100 hours for Fe-N-C. Density-functional theory calculations showed that the FeCu-N-C dual-metal catalysts got lower overpotential of 0.50 V than Fe-N-C (0.53 V), which improved the ORR activity. The results are helpful for the deep understanding of high-performance diatomic catalysts.

Introducing La into a Customized Dual Cu Covalent Organic Framework to Steer CO2 Electroreduction Selectivity from C2H4 to CH4.

Customizing multi-metal site catalysts for achieving controllable CO2 reduction reaction (CO2RR) product tuning holds immense promise yet poses formidable challenges. The traditional synthesis method of multi-metal sites is the pyrolysis of metal-containing precursors, which is inherently uncontrollable. Herein, a bottom-up strategy is employed to customize and synthesize multi-metal sites in covalent organic frameworks(COFs), aiming to controllably switch the CO2 reduction selectivity by regulating the electronic structure of active sites. Briefly, La element provides chances for manipulating and finetuning the electronic structure of the customized dual Cu sites, and converts the main catalytic product of CO2RR from ethylene to methane. Density functional theory calculations show that the introduction of La alters the electronic structure around Cu, enhances CO2 and H2O activation, and changes the formation of energy barriers of key intermediates. To the best of the author's knowledge, this study constructed the first example of customized multi-metal site COF catalysts and provided new ideas for controllable modulation of products.

Mn Doping at High-Activity Octahedral Vacancies of γ-Fe2O3 for Oxygen Reduction Reaction Electrocatalysis in Metal-Air Batteries.

γ-Fe2O3 with the intrinsic cation vacancies is an ideal substrate for heteroatom doping into the highly active octahedral sites in spinel oxide catalysts. However, it is still a challenge to confirm the vacancy location of γ-Fe2O3 through experiments and obtain enhanced catalytic performance by preferential occupation of octahedral sites for heteroatom doping. Here, a Mn-doped γ-Fe2O3 incorporated with carbon nanotubes catalyst was developed to successfully achieve preferential doping into highly active octahedral sites by employing γ-Fe2O3 as the precursor. Further, the vacancy in γ-Fe2O3 was only located on octahedral sites rather than tetrahedral ones, which was first proved by direct experimental evidence through the clarification doping sites of Mn. Notably, the catalyst shows outstanding activity towards oxygen reduction reaction with the half-wave potential of 0.82 V and 0.64 V vs. reversible hydrogen electrode in alkaline and neutral electrolytes, respectively, as well as the maximum power density of 179 mWcm-2 and 403 mWcm-2 for Mg-air batteries and Al-air batteries, respectively. It could be attributed to the synergistic effect of the doping Mn on octahedral sites and the substrate γ-Fe2O3 along with the modification of the adsorption/desorption properties for oxygen-containing intermediates as well as the optimization of the reaction energy barriers.

In/Outside Catalytic Sites of the Pore Walls in One-Dimensional Covalent Organic Frameworks for Oxygen Reduction Reaction.

Pore channels play a decisive role in mass transport in catalytic systems. However, the influences of the location of catalytic sites inside or outside of the pore walls on the performance were still under-explored due, because it is difficult to construct sites anchored in or outside of pore walls. Herein, one-dimensional covalent organic frameworks with precisely anchored active sites were used to explore the effects of channels on a typical oxygen reduction reaction (ORR) catalysis. Electrocatalytic evaluations showed that single Pt sites located inside of the channels exhibited higher kinetic activity compared to those anchored outside. The in situ spectroscopic analysis revealed that local reconstruction of Pt-Cl breaking and potential-induced anion transport occurred more effectively inside the channels. The superior anion transportability and kinetic activity of the inside-channel active sites also facilitated *OH desorption during the ORR process outperforming their outside-channel counterparts. The results of this study provide strategies for designing active sites in porous catalysts for heterogeneous catalysis.

Target-Modified Main Catalytic Site of CuZn Dual-Atom Catalysts for Promoting Methane Oxidation to Methanol: A DFT Study

Target-Modified Main Catalytic Site of CuZn Dual-Atom Catalysts for Promoting Methane Oxidation to Methanol: A DFT Study

In/Outside Catalytic Sites of the Pore Walls in One‐Dimensional Covalent Organic Frameworks for Oxygen Reduction Reaction

Pore channels play a decisive for mass transport in catalytic systems. However, the influences of the location of catalytic sites inside or outside of the pore walls on the performance were still under‐explored due, because it is difficult to construct sites anchored in or outside of pore walls. Herein, one‐dimensional covalent organic frameworks (COFs) with precisely anchored active sites were used to explore the effects of channels on a typical oxygen reduction reaction (ORR) catalysis. Electrocatalytic evaluations showed that single Pt sites located inside of the channels exhibited higher kinetic activity compared to those anchored outside. The in situ spectroscopic analysis revealed that local reconstruction of Pt–Cl breaking and potential‐induced anion transport occurred more effectively inside the channels. The superior anion transportability and kinetic activity of the inside‐channel active sites also facilitated *OH desorption during the ORR process outperforming their outside‐channel counterparts. The results of this study provide strategies for designing active sites in porous catalysts for heterogeneous catalysis.

Mn Doping at High‐Activity Octahedral Vacancies of γ‐Fe2O3 for Oxygen Reduction Reaction Electrocatalysis in Metal‐Air Batteries

γ‐Fe2O3 with the intrinsic cation vacancies is an ideal substrate for heteroatom doping into the highly active octahedral sites in spinel oxide catalysts. However, it is still a challenge to confirm the vacancy location of γ‐Fe2O3 through experiments and obtain enhanced catalytic performance by preferential occupation of octahedral sites for heteroatom doping. Here, a Mn‐doped γ‐Fe2O3 incorporated with carbon nanotubes catalyst was developed to successfully achieve preferential doping into highly active octahedral sites by employing γ‐Fe2O3 as the precursor. Further, the vacancy in γ‐Fe2O3 was only located on octahedral sites rather than tetrahedral ones, which was first proved by direct experimental evidence through the clarification doping sites of Mn. Notably, the catalyst shows outstanding activity towards oxygen reduction reaction with the half‐wave potential of 0.82 V and 0.64 V vs. reversible hydrogen electrode in alkaline and neutral electrolytes, respectively, as well as the maximum power density of 179 mWcm−2 and 403 mWcm−2 for Mg‐air batteries and Al‐air batteries, respectively. It could be attributed to the synergistic effect of the doping Mn on octahedral sites and the substrate γ‐Fe2O3 along with the modification of the adsorption/desorption properties for ORR oxygen‐containing intermediates as well as the optimization of the reaction energy barriers.

Improving SO2 Tolerance and Low-Temperature Denitrification Performance in NH3-SCR Catalysis: A Comprehensive Study on Nb and Mn Modified CeO2 Catalysts

In pursuit of improving the performance of MnCe-based catalysts in NH3-assisted selective catalytic reduction (NH3-SCR) of NOx technology, particularly their SO2 resistance and low-temperature activity, a series of NbMnCeOx catalysts were synthesized. Results reveal that the Nb0.1Mn2Ce5Ox catalyst provides the most excellent SO2 resistance and SCR catalytic activity. Incorporating Nb into the MnCeOx structure enriches the formation of additional chemisorbed oxygen species and surface acidity, promoting NO2 production while effectively preventing the over-oxidation of NH3 to produce N2O. The incorporation of Nb and Mn into CeO2 improves the content of Brønsted- and Lewis-acid sites, facilitating the NH3 capture and NH4+ generation, thus enabling the NH3-SCR process via both Eley-Rideal (E-R, Mechanism S1) and Langmuir-Hinshelwood (L-H, Mechanism S2) mechanisms, with the latter dominating at low temperatures. Nb doping considerably reduces the sulfate formation and the initial SO2 adsorption on the NbMnCeOx surface, while decreasing the average oxidation state of Mn and shielding it from electronic attack from S4+ in SO2. This study highlights the synergistic effect of Nb and Mn in bolstering acidic sites in CeO2-based catalysts and proposes the reaction mechanisms for improving the low-temperature and sulfur-resistant NH3-SCR performance.

Two-Dimensional Bi2Se3 Nanosheets Synthesis for Efficient Electrocatalytic Production of Ammonia from Nitrate

Ammonia (NH3), a critical component for various industries, is produced through the Haber-Bosch process, which, despite its importance, is a significant source of carbon emissions and operates on a centralized model, emphasizing the need for innovative solutions to decarbonize and decentralize its production. Electrochemical nitrate (NO3–) reduction to NH3 presents a promising alternative to the Haber-Bosch process for NH3 synthesis, with the added advantage of transforming waste into a valuable resource while mitigating water pollution concerns. However, achieving a well-defined active center and catalytic selectivity in the electrochemically driven reaction remains a significant challenge. In this study, we successfully fabricated a highly selective and active 2D Bi2Se3 catalyst, which demonstrated better performance in reducing NO3– to NH3 with a Faradaic efficiency (FE) of approximately 80% (−0.3V (RHE)) and a significant yield rate of 45mgh−1mgcat−1 (0.46 mmolh−1cm−2). Furthermore, the fabricated material exhibited exceptional stability and durability, maintaining a high NO3– reduction of 80% FE even after 10 consecutive cycles of extended use and continuous operation, demonstrating its remarkable resilience and reliability. Our findings show that the prepared catalyst selectively promotes the electrochemical reduction of NO3– to NH3 while suppressing the competing hydrogen evolution reaction (HER). The charge density profile indicates a pronounced charge localization around the Se atoms, implying that the Se active sites in the 2D Bi2Se3 catalyst act as the active center for the NO3– reduction mechanism, playing a crucial role in facilitating the reaction kinetics.

Ciprofloxacin degradation over Co3O4 catalysts by the microwave-assisted persulfate oxidation: a critical role of coordination composition

The combination of catalysts and microwave (MW) effects presents an emerging approach for persulfate (PS) activation, while the effect of active sites of catalysts on the synergistic reaction remains poorly understood. Here, we regulated the coordination composition of Co3O4 by strategically controlling the oxygen atmosphere during fabrication. We found that Co3+ and Co2+ acted as reactive centers for microwave absorption and catalytic activation of persulfate, respectively. By altering the ratio between Co3+ and Co2+, we explored the Co3O4 (2.23)-550 catalysts with significantly improved synergistic activity for degrading ciprofloxacin (CIP), which was 33.0 and 26.8 times higher than PS- Co3O4 (2.23)-550 (without microwave) and MW- Co3O4 (2.23)-550 (without persulfate), respectively. Meanwhile, Co3O4 (2.23)-550 catalyst (0.5mgL-1) showed the highest degradation rate of CIP 92.6% (0.5mgL-1) within 10min under microwave. According to the radical identification and intermediate analysis, the efficient degradation of CIP was ascribed to both free radical and non-free radical pathways. Thus, this work raises new insights into the structure-activity relationship of catalysts, and provides an efficient way to eliminate antibiotics via synergistic catalysis.

Accurate location of Ni and W active sites in hierarchical zeolite catalyst for the conversion of cellulose to alcohols

The process of converting cellulose into short-chain alcohols is a critical component of biomass valorization. In this study, we utilized an anion-cation co-directed hydrothermal method and wet impregnation to synthesize a hierarchical MFI zeolite with isolated Ni and W sites. We employed linear correlation analysis to evaluate the influence of pore size, site accessibility, and acidity on product selectivity. Balancing hydrogenation and acidic sites on the catalyst enhanced retro-aldol condensation and hydrogenation during cellulose conversion. Surface acidic sites accelerated glucose retro-aldol condensation, while micropore acidic sites aided in ethylene glycol hydrogenolysis. The close proximity of Ni and W facilitated high selectivity and yield of ethanol through bimetallic synergy. This research presented a novel strategy for preparing hierarchical zeolites with isolated metal sites and provides clarity on the cooperative roles of active sites in Ni-W bimetallic catalysts for cellulose conversion.

Synchronous introduction of S into Cu3BiS3 bi-active sites catalyst for synergistic electrocatalysis towards the conversion of CO2 into HCOOH

The construction of Cu-Bi bimetallic active sites presents a promising strategy to enhance the efficiency of electrocatalytic carbon dioxide reduction (CO2RR). However, achieving an optimal combination of Cu and Bi remains a significant challenge. In this work, we employed a straightforward one-pot hydrothermal method to synchronously introduce sulfur (S) into Cu-Bi catalysts. This approach facilitated an ingenious combination of Cu, Bi and S, resulting in strong synergistic interaction between the dual active sites. These interactions enhance the electrochemical active surface area (ECSA) and promote rapid electron transfer. As-synthesized Cu3BiS3 exhibits a unique capsule-like morphology and demonstrates superior electrocatalytic performance for CO2RR, achieving a Faradaic efficiency for formate production (FEHCOOH) of 88.8% at -0.986 V. Especially, the current density for HCOOH (JHCOOH) can reach 25.48 mA cm-2, accompanied by a long-term catalytic stability.

Rational Design of Supported Metal Catalysts for Selective Hydrogenation of Sulfur‐Containing Compounds

AbstractHydrogenation of nitro, carbonyl groups, and unsaturated bonds of sulfur‐containing compounds over supported metal catalysts is a green process in the production of building blocks of bioactive natural compounds, drugs, pesticides, and so forth, but it is a challenging task due to the strong coordination and complexation of the lone pair electrons in sulfur atom with active sites in catalyst, leading to dramatically reduced activity. Previous studies emphasize the sulfur‐resistant properties of catalysts in the hydrogenation of industrial feedstocks, but the direct hydrogenation of sulfur‐containing compounds has received limited attention. In this concept, recent advances in the hydrogenation of sulfur‐containing compounds were reviewed, including the strategies to improve the resistance of supported metal catalysts to sulfur poisoning. Finally, we give future perspectives on the development of efficient catalysts for the hydrogenation of sulfur‐containing compounds, and key factors influencing the hydrogen dissociation and migration in the presence of sulfur atoms are highlighted.

Understanding the Impact of Porous Transport Layers on Anion Exchange Membrane Electrolyzer Performance

Anion exchange membrane water electrolysis (AEMWE) is a promising technology for the low-cost production of green hydrogen. However, significant improvements in components and component integration are needed to improve the efficiency and lifetime of AEMWE devices. [1] The anode catalyst layer is critical to activity due to the large overpotentials associated with the sluggish kinetics of the oxygen evolution reaction (OER) and to durability due to the highly oxidizing environment that can lead to catalyst and polymer degradation. The anodic overpotential can be improved by increasing the number of catalyst sites that are utilized for the reaction, which requires the formation of uniform catalyst layers with good interfaces with both the membrane and the porous transport layer (PTL). [2] The PTL serves several important roles in the electrolyzer, including the transport of electrons between catalyst sites and the current collector and the transport of gaseous products out of the catalyst layer. The PTLs used for AEMWE are typically Ni-based, with no precious metal coating or microporous layer. The morphology of the PTL impacts its interface with the catalyst layer, which affects in-plane electronic resistance and the ability to utilize catalyst sites effectively. [3] The porosity and pore size of the PTL also affect bubble removal, which can contribute significantly to mass transport overpotential, particularly at high current densities. Commercially available PTLs are often not designed for the AEMWE application, meaning that their properties are not optimized for these two critical functions. In addition, in a supporting electrolyte like potassium hydroxide, hydroxide ions are not restricted to the catalyst layer-membrane interface or to the ionomer network such that the PTL also contributes to catalytic activity. Ni alloy PTLs can provide an advantage of higher initial catalytic activity compared to standard Ni, but many dopant metals (i.e., Fe, Cr, etc.) are prone to dissolution under AEMWE operating conditions, which can damage the membrane and lead to higher rates of degradation. Improved PTL designs are needed to improve electrolyzer performance and durability.In this study, we investigate the impact of PTLs with varying morphology and composition on kinetics, catalyst layer resistance, and durability. The properties of the PTLs, including composition, crystal structure, thickness, porosity, and fiber dimensions are determined using spectroscopy, diffraction, electron microscopy, and micro X-ray tomography. These material properties are then correlated with the performance of the PTL, with and without an additional catalyst layer. As shown in Figure 1, the PTLs have a significant effect on device performance and often have significant electrochemical activity in the absence of a catalyst layer. The impact of the PTL on performance trends with catalyst conductivity and loading is also explored. Electrochemical impedance spectroscopy (EIS) is further used to understand the effect of the PTL on interfacial charge resistance and resistances within the catalyst layer. Finally, ex situ characterization of the catalyst layer and PTL with scanning electron microscopy and X-ray spectroscopy, as well as analysis of dissolved species in the electrolyte using an inductively coupled-mass spectrometer (ICP-MS), are used to understand the material stability of the PTL and impacts of PTL degradation on overall durability. This work provides insight into PTL design principles, which can be used to improve the performance and lifetime of AEM electrolyzers.