Performance Of Catalysts Research Articles

Densely populated single‐atom catalysts for boosting hydrogen generation from formic acid

AbstractThe single‐atom M‐N‐C (M typically being Co or Fe) is a prominent material with exceptional reactivity in areas of catalysis for sustainable energy. However, the formation of metal nanoparticles in M‐N‐C materials is coupled with high‐temperature calcination conditions, limiting the density of M‐Nx active sites and thus restricting the catalytic performance of such catalysts. Herein, we describe an effective decoupling strategy to construct high‐density M‐Nx active sites by generating polyfurfuryl alcohol in the MOF precursor, effectively preventing the formation of metal nanoparticles even with up to 6.377% cobalt loading. This catalyst showed a high H2 production rate of 778 mL gCat−1 h−1 when used in the dehydrogenation reaction of formic acid. In addition to the high density of the active site, a curved carbon surface in the structure is also thought to be the reason for the high performance of the catalyst.

Lattice Strain Regulated by Hetero/Homo Atom Interface Merging on NiMo Nanocluster for High-Performance Hydrogen Production.

Lattice strain engineering represents a cutting-edge approach capable of delivering enhanced performance across various applications. The lattice strain can affect the performance of electrochemical catalysts by changing the binding energy between the surface-active sites and intermediates. In this work, lattice strain is regulated through a homo/heterogeneous atomic interface merging. The strong lattice strain and electronic interactions between Ni and Mo facilitated the reaction kinetic of HER. The prepared NiMo@SSM exhibits excellent HER catalytic performance with 70 mV overpotential at the current density of 10 mA cm-2 and long-term stability. The method of controlling lattice strain through hetero/homo atom interface merging provides a new strategy for designing high-performance alkaline HER electrocatalysts.

Enhanced Platinum-Based Thin-Film Catalysts for Electro-Oxidation of Methanol

Surface morphology is one of the critical factors affecting the performance of electrocatalysts. Thus, with careful manipulation of the surface structures at the atomic level, the effectiveness of the catalyst can be significantly improved. Heat treatment is an effective method for inducing surface atom rearrangement, hence modifying the catalyst’s characteristics. This study investigated the substrate’s influence and the effect of thermal annealing on the morphology and surface reconstruction of platinum (Pt) thin-film catalysts. Our findings indicate that heat treatment in a reductive atmosphere (95% Ar + 5% H2) at 300 °C can significantly impact the degree of rearrangement of surface atoms. This process induces long-range ordering, resulting in domains with a high proportion of (111) and (100) sites without an epitaxial template. Considering that the reactivity of low-index platinum single crystals for the methanol oxidation reaction follows the following sequence Pt(111) < Pt(110) < Pt(100), increasing the proportion of (100) planes leads to a notable enhancement (up to three times) in performance, compared to untreated catalysts. Furthermore, considering the amount of precious metal consumed, a mass-specific current density obtained on annealed Pt@Ni is larger by one order of magnitude and ~2 times that obtained on Pt@Cr and Pt@GCox catalysts, respectively. Our results demonstrate that an easy-to-implement way of controlling atomic orientations improves catalyst performance. With this contribution, we propose a method for designing improved electrocatalysts, as catalytic reactions occur only at the surface.

Spinel-Based Catalysts That Enable Catalytic Oxidation of Volatile Organic Compounds.

Volatile organic compounds (VOCs) have caused serious harm to human health and ecological environment, and have received much attention in recent years. Despite the successful applications of catalytic combustion of VOCs as the core technology of VOCs removal in industry, the development of efficient catalysts that can mineralize VOCs into nontoxic CO2 and H2O at low temperatures remains a great challenge. Recent studies show that spinel-based materials as efficient catalysts were extensively used in the catalytic oxidation VOCs field due to their synergistic effect, manifold compositions, and electron configurations. However, most of the pollutants are complex, consisting of multiple VOCs, water vapor, CO2, SO2 and other substances, which presents a significant challenge in constructing highly active and stable catalysts. To meet the future demand for efficient catalysts capable of removing various types of VOCs, it is urgent to rationally design and scientifically prepare spinel catalysts based on existing knowledge. This work reviews the research and development of various spinel catalysts with an emphasis on their catalytic performance in VOCs oxidation. The catalytic performance of spinel-based catalysts for different sorts of VOCs was summarized and compared. Moreover, the effects of the reaction conditions on the catalytic performance of spinel-based catalysts were examined to accommodate complicated operating conditions. Subsequently, the regulation of spinel oxides in structure and defect was coherently reviewed to guide the development and design of efficient catalysts. Especially, the research techniques for the reaction mechanism over spinel catalysts were displayed to better deepen the understanding of catalytic oxidation of VOCs. Finally, the current development and challenges were proposed and put forward for future research. This review provided a systematic understanding of the VOCs oxidation over spinel-based catalysts and offered guidance for the development of high-performance catalysts for VOCs elimination.

A Heterogeneous Phosphomolybdate Nanocatalyst Utilizes Vitamin B1 to Promote Solvent‐Free H2O2 Sulfoxidation Selectivity

ABSTRACTCatalyst design and fabrication with safe and affordable components and methods is a high‐value‐added business. In this work, a vitamin‐based hybrid nanomaterial (PMoB1) is prepared by simple stirring of thiamine hydrochloride (vitamin B1, VB1) as an inexpensive commercially available biologically active compound with phosphomolybdic acid (PMo12) in acidic aqueous solution to catalyze selective oxidation of sulfides using aqueous H2O2. A small amount of this heterogeneous catalyst drives rapidly the sulfoxidation reaction under mild and solvent‐free conditions facilitating the product separation and reducing significantly the environmental impacts. The main factors of the catalytic reaction were optimized by the central composite design (CCD) method. The solid catalyst tolerates a wide range of pH and retained its structural integrity even at alkaline solution (pH = 11). PMoB1 composed of two VB1 and one PMo12 was found to be partially reduced based on 13P NMR and UV–Vis spectra. An amorphous structure with aggregated nanoparticles with sizes ranging between 50 and 70 nm and a specific surface area of 35 m2/g are important reasons for enhanced catalytic activity and selectivity. Nevertheless, non‐covalent interactions such as hydrogen bonding and the π–π stacking can also significantly affect the catalyst performance. Given the scavenging tests and spectral evidences, a non‐radical mechanism involving peroxo species is postulated. The catalysis is shown to be truly heterogeneous while the solid catalyst largely maintains its structural integrity during the recycling test.

Ni-Co Bimetallic Catalysts Supported on Mixed Oxides (Sc-Ce-Zr) for Enhanced Methane Dry Reforming.

Dry methane reforming (DRM) presents a viable pathway for converting greenhouse gases into useful syngas. Nevertheless, the procedure requires robust and reasonably priced catalysts. This study explored using cost-effective cobalt and nickel combined into a single catalyst with different metal ratios. The reaction was conducted in a fixed reactor at 700 °C. The findings indicate that the incorporation of cobalt significantly enhances catalyst performance by preventing metal sintering, improving metal dispersion, and promoting beneficial metal-support interactions. The best-performing catalyst (3.75Ni+1.25Co-ScCeZr) achieved a good conversion rate of CH4 and CO2 at 46.8 %, and 60 % respectively after 330 minutes while maintaining good stability. The TGA and CO2-TPD analysis results show that the addition of Co to Ni reduces carbon formation, and increases the amount of strong basic sites and isolated O2- species, and the total amount of CO2 desorbed. These results collectively highlight the potential of cobalt-nickel catalysts for practical DRM applications and contribute to developing sustainable energy technologies.

Improved Catalyst Performance for the Oxygen Evolution Reaction under a Chiral Bias

Improved Catalyst Performance for the Oxygen Evolution Reaction under a Chiral Bias

Catalytically Active Site Mapping Realized through Energy Transfer Modeling

AbstractThe demands of a sustainable chemical industry are a driving force for the development of heterogeneous catalytic platforms exhibiting facile catalyst recovery, recycling, and resilience to diverse reaction conditions. Homogeneous‐to‐heterogeneous catalyst transitions can be realized through the integration of efficient homogeneous catalysts within porous matrices. Herein, we offer a versatile approach to understanding how guest distribution and evolution impact the catalytic performance of heterogeneous host–guest catalytic platforms by implementing the resonance energy transfer (RET) concept using fluorescent model systems mimicking the steric constraints of targeted catalysts. Using the RET‐based methodology, we mapped condition‐dependent guest (re)distribution within a porous support on the example of modular matrices such as metal–organic frameworks (MOFs). Furthermore, we correlate RET results performed on the model systems with the catalytic performance of two MOF‐encapsulated catalysts used to promote CO2 hydrogenation and ring‐closing metathesis. Guests are incorporated using aperture‐opening encapsulation, and catalyst redistribution is not observed under practical reaction conditions, showcasing a pathway to advance catalyst recyclability in the case of host–guest platforms. These studies represent the first generalizable approach for mapping the guest distribution in heterogeneous host–guest catalytic systems, providing a foundation for predicting and tailoring the performance of catalysts integrated into various porous supports.

Enhanced H2S removal efficiency using CuO/Al2O3 catalyst impregnated with Ca(NO3)2: Influence of calcination temperature and mechanistic insights

A series of Ca(NO3)2-CuxO/Al2O3 catalysts with different calcination temperatures were designed to remove H2S effectively. Experimental and characterization results indicate that the calcination temperature can influence the catalyst's specific surface area, basic sites, and oxygen vacancies (VOs) concentration, thereby promoting its desulfurization performance. The Ca(NO3)2-CuxO/Al2O3 catalyst, calcined at 230 °C, exhibits an optimal surface structure. It demonstrates optimal H2S desulfurization performance at a temperature of 60 °C and relative humidity of 60 %, achieving a removal capacity of 486.67 mg/g. The VOs in CuxO (CuO and Cu2O) induce a unique catalytic of H2O, which generates hydroxy radicals (·OH) to oxidize the H2S anion to S. The introduction of Ca2+ provides basic sites to buffer pH, and NO3- with H+ removes H2S through cyclic oxidation, significantly enhancing the desulfurization performance of the Cu-based catalyst. The CaO-CuxO/Al2O3 catalyst, calcined at 700 °C, suffers from a deteriorated catalyst structure, leading to the rapid formation of desulfurization by-products due to the presence of CaO covering the catalyst surface. This diminishes the effectiveness of Cu, significantly impairing the catalyst's desulfurization performance (150.47 mg/g). Consequently, desulfurization mechanisms of Ca(NO3)2-CuxO/Al2O3 and CaO-CuxO/Al2O3 are proposed, offering effective strategies for the design and optimization of subsequent high-efficiency catalysts.

Strategies and Mechanisms to Improve the Catalytic Performance of Cu-Based Catalyst for CO2 Electrochemical Reduction Reaction to Methane

This article introduces three significant ways of producing methane by electrocatalytic reduction of carbon dioxide. Electrocatalytic reduction of carbon dioxide can efficiently convert CO2 molecules into various high-energy fuels under ambient conditions. Methane gas, among them, stands out due to its relatively high calorific value, chemical stability, ease of storage and transportation. Therefore, research on electrocatalytic reduction of CO2 to generate methane is crucial. Common methods include adjusting catalyst morphology to expose more active sites, building nanoscale catalysts results in smaller-sized nanostructured copper and combining copper with other metals to form alloys, creating multi-metal catalysts. By optimizing these catalysts, we can efficiently reduce carbon dioxide into methane.

Development and Application of Green Catalysts: Challenges, Optimization, and Future Perspectives

This paper comprehensively reviews the development and application of green catalysts in modern chemical industries, with a focus on analyzing the significant advantages of various types of green catalysts, such as metal-organic frameworks (MOFs) and enzyme catalysts, in improving reaction efficiency, reducing energy consumption, and minimizing by-product generation. The paper delves into the design and synthesis of green catalysts, optimization of reaction conditions, and technologies for catalyst recycling and regeneration, highlighting their key roles in enhancing catalyst performance. Despite challenges such as high material costs, complex synthesis processes, and issues with stability and durability in practical applications, continuous technological innovation and process improvements offer promising solutions. As global attention to sustainable development grows, green catalysts are expected to have broad applications in emerging fields such as carbon capture and utilization, renewable energy conversion, and environmental remediation, thereby driving the green transformation and low-carbon development of the chemical industry and providing strong technical support for achieving global sustainability goals.

Research Progress in the Composition and Performance of Mn-Based Low-Temperature Selective Catalytic Reduction Catalysts

NH3 selective catalytic reduction (NH3-SCR) is the most prevalent and effective method for removing nitrogen oxides. Over the past few decades, manganese (Mn)-based catalysts have demonstrated strong catalytic activity and have been extensively studied for low-temperature NH3-SCR reactions. This paper provides an in-depth introduction to four forms of Mn-based catalysts: single manganese oxide-based catalysts, binary Mn-based metal oxide catalysts, ternary and multivariate Mn-based metal oxide catalysts, and nano-Mn-based catalysts. Advances have been made in enhancing Mn-based catalysts’ redox performance and acidity, increasing the active component’s dispersion, lowering binding energy, enlarging specific surface area, raising the Mn4+/Mn3+ ratio, and enriching surface adsorbed oxygen by optimizing preparation methods, altering the oxidation state of active components, modifying crystal phases, and adjusting morphology and dispersion, along with various metal modifications. The mechanism of low-temperature NH3-SCR reactions has been elucidated using various characterization techniques. Finally, the research directions and future prospects of Mn-based catalysts for low-temperature NH3-SCR reactions are discussed, aiming to accelerate the commercial application of new Mn-based catalysts.

Discovery of Alloy Catalysts for Ammonia Decomposition by Machine Learning-Based Prediction of Adsorption Energies

Ammonia decomposition has gained significant attention as an eco-friendly method for hydrogen production because it creates no carbon dioxide emissions. While Ru catalysts are known for their high activity in ammonia decomposition, their high cost makes them uneconomical for commercial use. Therefore, it is essential to explore novel alloy catalysts composed of inexpensive elements with high catalytic performance. Nitrogen adsorption energies serve as key descriptors indicating the catalytic performance for ammonia decomposition, and first-principle calculations can compute these energies. However, the screening of numerous alloy catalyst candidates through extensive first-principle calculations and experimental validations remains time-consuming due to the vast number of potential candidates. To address this, artificial intelligence and machine learning models are being developed to quickly predict catalyst performance, efficiently searching for promising catalyst candidates. In this study, we developed a machine-learning-based method to rapidly predict nitrogen adsorption energies using a graph-based artificial neural network, thereby efficiently searching for novel catalysts for ammonia decomposition. Our training dataset included the nitrogen adsorption energies of 30 pure transition metal catalyst candidates, as well as binary alloy catalyst candidates, including core-shell and intermetallic compounds. As a result, we successfully identified 12 catalyst candidates composed of inexpensive elements that are likely to exhibit catalytic performance comparable to Ru catalysts.

Effect of modified Fe2O3/activated carbon catalysts for low-temperature CO selective catalytic reduction of NOx in underground diesel vehicle exhaust

The elimination of CO and NOx has practical significance for the control of exhaust pollutants from underground diesel vehicles. Catalytic reduction of NO by CO (CO-SCR) using activated carbon (AC) catalysts is considered a cost-effective and environmentally friendly denitrification method. In this study, Fe2O3/AC-based catalysts were prepared using an impregnation method and modified with different metals to investigate their impact on catalyst performance. The results demonstrated that the catalyst exhibited the highest denitrification efficiency when loaded with 10% Fe. The Mn-doped 10Fe/AC catalyst exhibited the best catalytic performance, with the highest NO conversion of 97.5% and CO removal rate of 83.3% at 240 °C. The effects of loading Mn, Ce, and La on the physical and chemical properties of the catalysts were analyzed using various characterization tools, and the reaction mechanism of the catalysts was investigated by in situ DRIFTS technique. The findings revealed that the strong synergistic interaction occurring between Mn and Fe led to an increase in the surface-adsorbed oxygen (Oα) and Fe3+, which produced more oxygen vacancies on the catalyst, thus improving the redox properties. The in-situ DRIFT results indicated that the addition of Mn enhanced the adsorption capacity of active NO and CO. For the CO-SCR reaction on Fe-Mn/AC catalyst, the E-R mechanism was followed at low temperature and the L-H mechanism was followed at high temperature.

Influence of Annealing Temperature on the OER Activity of NiO(111) Nanosheets Prepared via Microwave and Solvothermal Synthesis Approaches.

Earth-abundant transition metal oxides are promising alternatives to precious metal oxides as electrocatalysts for the oxygen evolution reaction (OER) and are intensively investigated for alkaline water electrolysis. OER electrocatalysis, like most other catalytic reactions, is surface-initiated, and the catalyst performance is fundamentally determined by the surface properties. Most transition metal oxide catalysts show OER activities that depend on the predominantly exposed crystal facets/surface structure. Therefore, the design of synthetic strategies to obtain the most active crystal facets is of significant research interest. In this work, rock salt NiO OER catalysts with (111) predominantly exposed facets were synthesized by a solvothermal (ST) method either heated under supercritical or microwave-assisted (MW) conditions. Particular emphasis was placed on the influence of the post annealing temperature on the structural configuration and OER activity to compare their catalytic performances. The as-prepared electrocatalysts are pure α-Ni hydroxides which were converted to rock salt NiO (111) nanosheets with hexagonal pores after heat treatment at different temperatures. The OER activity of the electrodes has been evaluated in 0.1 M KOH using geometric and intrinsic current densities via normalization by the disk area and BET area, respectively. The lowest overpotential at a geometric current density of 10 mA/cm2 is found for samples pretreated by heating between 400 and 500 °C with a catalyst loading of 115 μg/cm2. Despite the very similar nature of the catalysts obtained from the two methods, the ST electrodes show a higher geometric and intrinsic current density for 500 °C pretreatment. The MW electrodes, however, achieve an optimal geometric current density for 400 °C pretreatment, while their intrinsic current density requires pretreatment over 600 °C. Interestingly, pretreated electrodes show consistently higher OER activity as compared to the poorly crystalline/less ordered hydroxide as-prepared electrocatalysts. Thus, our study highlights the importance of the synthesis method and pretreatment at an optimal temperature.

DLP 3D printing of alumina catalyst architectures: Design, kinetics and modeling of structure effects on catalyst performance

DLP 3D printing of alumina catalyst architectures: Design, kinetics and modeling of structure effects on catalyst performance

Extra-framework cations promoted zeolite-encaged cobalt catalysts towards efficient ethylbenzene dehydrogenation

The transformation of ethylbenzene to styrene through direct dehydrogenation is essential process in chemical industry, indispensable for the synthesis of polymers and plastics. Herein, faujasite zeolite encaged cobalt catalyst with potassium ion as the extraframework cations, namely K-Co@Y, is reported to be a robust catalyst for ethylbenzene direct dehydrogenation, showing ethylbenzene conversion of ∼45 % and styrene selectivity of ∼95 % simultaneously under employed conditions. The superior performance of K-Co@Y in comparison with Na-Co@Y is attributed to the effective modulation of zeolite-encaged Co2+ species by extraframework K+ ions, which increases the electron density of cobalt sites and facilitates CH bond activation. Although coke deposits cause gradual deactivation, the structural integrity of K-Co@Y can be well preserved during the dehydrogenation reaction and the performance can be full restored via a simple calcination regeneration step, making K-Co@Y an eligible catalyst for long-term running in the continuous regeneration mode. This study highlights the vital role of extraframework cations in zeolite-encaged single-site catalysts for target chemical transformations and opens up a new way to modulate the performance of zeolite catalysts.

Efficient catalytic oxidation of xylose to formic acid with the oxygen vacancies of CeO2 promoted the vanadium catalysts anchored on biochar

The catalytic oxidation of carbohydrates for the preparation of formic acid (FA) is an prominent route for high-value utilisation of biomass. Reforming xylose, a biomass derivative, into FA with high efficiency is essential for the advancement of non-homogeneous V-type catalysts. Here, we present the self-assembly of V and Ce onto a cellulose pulp for the synthesis of oxygen vacancy (Ov)-rich non-homogeneous-bimetallic catalysts (5Ce-VOx/BC-600). Under the optimised conditions, 71.46 % FA was obtained, which far exceeded the catalytic performance of the single-metal catalyst. Furthermore, the 5Ce-VOx/BC-600 catalyst showed excellent stability and reusability. Kinetic studies revealed that glyceric and glycolic acids served as the pivotal intermediates, undergoing subsequent deacidification and oxidation processes to yield FA and CO2. The analysis of the catalytic mechanism indicated that the incorporation of Ce enhanced the quantity of acidic sites and the concentration of Ov in the 5Ce-VOx/BC-600 catalyst, which promoted substrate adsorption and O2 activation. Meanwhile, the catalyst showed high lattice oxygen (OL) mobility and assisted the redox cycle of V5+/V4+ to oxidise xylose to FA. Significantly, the synergistic effect of Ce, V species and Ov enhances the OL mobility of the catalysts, thus promoting the efficient oxidation of xylose. The catalytic system was further extended to the oxidation of other biomass derivatives to FA, demonstrating excellent catalytic performance.

Computational screening and investigation of ligand effect on TM single atom catalyst for hydrogen evolution reaction

Here, we studied the stability, electronic characteristics, and HER catalytic performance of a transition metal single atom catalysts, both with and without the presence of chlorine ligand. The findings indicate that all catalysts, except for Au, Au-Cl, Ag, Ag-Cl, are thermodynamically stable. We found 3d transition metals are more stable than those in the 4d and 5d series. Ag-Cl, Sc, Ag, Fe-Cl, and Cr-Cl have the poorest electrochemical stability. We found a negative Pearson correlation between Fermi energy and formation energy for TM-Cl, which is opposite to the trend observed for bare TM catalysts. The higher HER activity of chlorine bonded system for the early 3d TM suggests that the downshifting of the d-band center facilitates the activity. We also observed a periodic trend in the d-band center for both TM and TM-Cl systems. Mn-Cl, Cr-Cl, Ti-Cl, Fe-Cl, V-Cl and Zn emerged as the superior catalysts in our study series.

Catalytic cracking of methane to H2 and carbon over hydrotalcite-derived sintering-resistant NiVAl catalysts

Catalytic methane cracking produces pure H2 and high value-added carbon, a potentially environmentally friendly process for hydrogen production, but challenges remain in the designing of high-performance catalysts. NiVAl catalysts were obtained by reducing the hydrotalcite precursor, and the samples were analyzed by XRD, ICP, N2 adsorption-desorption, SEM, XPS, and the impacts of reaction temperature and V/Ni ratio on the production of H2 by cracking methane were studied. The results showed that the V doping could promote the reduction of Ni species, improve the specific surface area of the catalyst and inhibit the sintering of Ni particles. The methane cracking hydrogen yield curve illustrates that the performance of NiVAl catalyst shows a volcanic relationship with the V/Ni ratio. The Ni2.4V0.6Al catalyst exhibits optimal performance, with a stable hydrogen yield of about 80% for 210 min at 700 °C. In addition, the reaction temperature also significantly affects the catalyst performance, with high temperatures favoring increased catalytic activity and low temperatures tending to improve stability. The Ni2.4V0.6Al catalyst was reacted at 600 °C for 300 min with 68% hydrogen yield without deactivation.