High Activity Of Catalyst Research Articles

Salen-Pd(II)-Modified Stereoregular Polyisocyanides for Efficient Cooperative Catalysis of Suzuki Coupling Reaction.

The development of high activity catalysts is crucial for improving industrial efficiency and mitigating environmental pollution. Polyisocyanides, with their pendant groups capable of forming ordered adjacent structures, offer a promising framework for designing cooperative catalysts that mimic the functionality of bimetallic centers. This unique structural arrangement is anticipated to significantly enhance catalytic activity in cooperative reactions. A novel approach to enhance the Suzuki coupling reaction using polymer-supported catalysts is presented. In this study, stereoregular polyisocyanides with Salen-Pd are functionalized to produce the Pd(II) metalized polyisocyanide (P1-Pd). The rigid backbone of the polymer facilitates the parallel alignment of Salen-Pd pendants, enabling double activation of the two substrates at an average distance of ≈1.2nm. Catalytic efficiency is evaluated through Suzuki coupling reactions using various aryl halides. P1-Pd demonstrates high activity, yielding the desired products with excellent conversion rates. Conversely, the irregular polymer counterpart P2-Pd. P3-Pd and the small molecule control C1-Pd exhibit lower performance due to the absence of cooperative catalysis. To showcase the applicability of this strategy, Suzuki coupling is successfully conducted with outstanding yields for key drug intermediates, while also offering innovative insights for conjugated polymer synthesis.

Next Generation Cathode Catalyst Layer Design with High Oxygen Permeable Ionomer – Benefits, Challenges, and Prospects for Heavy Duty Fuel Cell Applications

Proton Exchange Membrane Fuel Cell (PEMFC) has a growing demand to power zero emission fuel cell applications. Ballard is the fuel cell industry leader, developing the next generation core technology to fulfill such demand and giving continuous efforts on cost reduction. Key requirements in fuel cell market applications include high power density and long-life operation, while maintaining high efficiencies and reducing costs. This places a high demand on improving catalyst performance and electrode layer transport, which can be sustained over the duration of the product lifetime. To reduce fuel cell membrane electrode assembly (MEA) cost, the push for high performance catalyst layers (CLs) with low platinum (Pt) loadings results in new challenges for the cathode material selection and electrode design. The increased oxygen transport resistance that occurs at lower catalyst loadings with reduced available catalyst electrochemical active surface area (ECSA), causes two very closely related challenges: 1) greater performance losses at high current density increases the difficulty to achieve the power requirements for the heavy duty market, and 2) the loss of catalyst ECSA via platinum dissolution over time puts additional demands on the design to achieve the end of life (EOL) performance requirement. Therefore, a combination of material solution, design choice and processing parameters are the key to optimize next generation cathode design for fuel cell applications1.One material solution to achieve high performance while reducing catalyst loadings is the development of high oxygen permeable ionomer (HOPI) that mitigates oxygen transport limitations at the Pt surface. Chemours has developed a HOPI with a bulky, sterically rigid monomer group in the ionomer backbone, which disrupts the packing density, improving oxygen permeability on the catalyst surface2. One of the key challenges of HOPI integration and the scale-able fabrication of the catalyst layer is high crack density of CL due to the rigid nature of the ionomer. Ballard has integrated HOPI in the cathode CL overcoming scale-able fabrication challenges through appropriate process parameter selection and evaluated CL performance. The use of accelerated testing and modeling approach developed by numerous product iteration, has been applied for lifetime estimation for HOPI technology introduction. In this talk, we will discuss details about benefit of High Oxygen Permeable Ionomer (HOPI) in next generation cathode CL design.Recently, key requirements in heavy-duty market applications are placing more importance on high efficiency rather than high power density to reduce fuel cost rather catalyst cost. Reaching the target lifetime, catalyst overloading to 0.45 mg/cm2 total Pt in anode and cathode, and 44% active membrane area oversizing are suggested3. Therefore, to achieve high efficiency target, high catalyst activity is more desired. Interestingly, HOPI also showed high specific activity due to the mitigation of catalyst poisoning by sulfonate anion groups4. We will also discuss the catalyst layer design prospect with HOPI for such transition on heavy duty market application.Acknowledgement: US Department of Energy (DOE) funded heavy duty MEA development project (DE-EE0008822).References M. Dutta, A. Young, V. Colbow, J. Bellerive and S. Knights 2020 Examining Catalyst Layer Design Strategies for Improved Fuel Cell Performance and Durability. ECS PRiME 2020S. Litster et al. 2020 Durable High-Power Density Fuel Cell Cathodes for Heavy-Duty Vehicle. DOE AMR 2020K. Ahluwalia and X. Wang 2024 Performance and Durability of Hybrid Fuel Cell Systems for Class-8 Long Haul Trucks. J. Electrochem. Soc. 171 034507R. Jinnouchi, K. Kudo and K. Kodama 2021 The role of oxygen-permeable ionomer for polymer electrolyte fuel cells. Nat Commun 12, 4956.

A Tantalum-Rich Pt-Ta-Co Electrocatalyst for Polymer Electrolyte Fuel Cells

Wide-spread use of fuel cell vehicles (FCVs) requires both high activity and high durability of catalysts for PEFCs. Especially, significant performance and durability improvement is required for application to heavy duty vehicles (HDVs) [1]. A variety of catalysts, such as Pt-Co alloy catalysts, have been studied and developed to increase catalytic activity, but further improvement is desirable for HDV applications [2]. Here in this study, we aim to improve performance and durability of Pt-Co catalysts by adding tantalum, which is stable under strongly-acidic PEFC conditions. Compared to catalysts on Ta-based catalyst support with a similar composition [3], Pt-Ta-Co catalysts are advantageous if these three elements (Pt, Ta, and Co) are loaded at the same time to prepare both catalyst support and alloy catalyst. Various Pt-Ta-Co catalysts (such as Pt:Ta:Co = 7:2:1)[4] were found to be superior to Pt catalyst with respect to degradation caused by load fluctuation. However, in PEFCs for FCVs, the degradation of the carbon support due to start-stop cycles has also to be suppressed [5]. In this study, Ta-rich catalysts (Pt:Ta:Co = 3:4:1, 3:2:1) were prepared by increasing the amount of Ta to Pt-Co to improve the durability against start-stop cycles. These Ta-rich compositions may minimize direct contact between Pt and carbon support by the separation to the Pt-Co and Ta-rich phases in the catalyst particles, forming a nanocomposite during the preparation process.Platinum acetylacetonate, tantalum ethoxide, and cobalt nitrate hydrate were used as precursors for catalyst preparation. These precursors were mixed with a dispersion in which mesoporous carbon (MC) support (MH-18, Toyo Tanso, Japan) was dispersed, dried, and heat-treated. The catalysts prepared were characterized by microstructural observation by STEM, and their electrochemical performance was evaluated.In Pt3Ta4Co1/MC, STEM images with EDS mapping in Figure 1 confirmed the presence of a Ta-rich phase around Pt-based catalysts, indicating the formation of nanocomposites. The initial performance of prepared catalysts (ECSA≈100 m2/g, MA≈600 A/g) measured by half-cell electrochemical measurements was better than the standard Pt/C catalyst (TEC10E50E, Tanaka Kikinzoku Kogyo, ECSA≈80 m2/g, MA≈250 A/g). In this presentation, load cycle durability measured by half-cell electrochemical measurements and start-stop cycle durability measured by MEA tests will also be presented and discussed. Acknowledgment This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). An educational part for young scientists was supported by the Japan Science and Technology Agency (JST) as a part of Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE), Grant Number JPMJAP2307. Reference A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers, and A. Kusoglu, Nat. Energy, 6, 462 (2021).Janssen, P. Weber, and M. Oezalan, Current Opinion in Electrochem., 40, 101337 (2023).Sanami, R. Nishiizumi, M. Masahiro, Z. Noda, S. M. Lyth, J. Matsuda, A. Hayashi, and K. Sasaki, ECS Trans., 112 (4), 369 (2023).Miyamoto, T. Ogawa, R. Nishiizumi, M. Masahiro, Z. Noda, M. Nishihara, A. Hayashi, J. Matsuda, and K. Sasaki, ECS Trans., 112 (4), 353 (2023).M. Roen, C. H. Paik, and T. D. Jarvi, Electrochem. Solid-State Lett., 7, A19 (2004). Figure 1

Effect of Bi Doping on the Kinetics of Nickel Oxides-Based Electrocatalyst in Alkaline Oxygen Evolution Reaction

As a generation process of hydrogen fuel, an alkaline water electrolysis is considered as one of the most promising pathway. The water electrolysis is able to divide into two half-cell reaction: hydrogen evolution reaction (HER) in cathode and oxygen evolution reaction (OER) in anode. However, high activation energy of OER is regarded as a major bottleneck for utilization of water electrolysis, therefore it is necessary to use an electrocatalyst to improve the reaction rate. Currently, commercially used electrocatalysts of OER is precious metal such as platinum (Pt), ruthenium (Ru), and iridium (Ir) based compound which have critical drawback for high cost and low stability in alkaline electrolyte.As a substitute of platinum group materials for electrocatalyst of oxygen evolution reaction (OER), the development of cost-effective and high-active nickel oxide catalyst has attracted intense research interest. Alkaline OER is composed by five states: M, M-OH, M-O, M-OOH, and M + O2, and the gibbs free energy of final state is 4.92 eV higher than the first state. Thus, the free energy difference between each states equally becomes 1.23 eV to minimize the activation energy of rate determining step (RDS). In this point, nickel oxide shows a remarkable catalytic activity because a rapid and reversible electrochemical oxidation on the surface of nickel oxide triggers reconstructions to form hydroxide which is suitable structures for intermediate of OER. However, the nickel oxide still has high activation energy of reaction step from nickel(II) oxide to nickel(III) oxyhydroxide (3rd step of OER, Ni-O à Ni-OOH), which becomes RDS of OER. Because the catalytic activity seriously reduces without the balanced rate between each step of reaction, it is necessary to control the electric structure of nickel oxide to optimize adsorption energy of intermediates.In this context, bismuth doped nickel oxide is synthesized for electrocatalyst of OER. Because bismuth has higher electronegativity than nickel, the adsorption energy of positively charged nickel with proton decreases and the adsorption energy of positively charged nickel oxide with hydroxide ion increases. Therefore, the activation energy of RDS of OER is expected to reduce than the pristine nickel oxide.In practice, the bismuth doped nickel oxide is synthesized by hydrothermal process and the composition of bismuth is controlled by the concentration of precursors. The crystal structure of nickel oxide is maintained after the addition of bismuth, but the inter-planar spacing of overall plane of nickel oxide structure decreases according to selected area electron diffraction (SAED) pattern of transmission electron microscopy (TEM). In this context, the bismuth additive does not form the bi-metal oxide with nickel, but it substitutes the nickel site of nickel oxide structure. According to the nickel 2p3/2 spectra of x-ray photoelectron spectroscopy (XPS), a binding energy of nickel oxide peak positively shifts when the composition of bismuth additive increased due to the shifted electron from nickel to bismuth atom. As electrochemical measurement for evaluation of catalytic activity, the bismuth doped nickel oxide shows 59 mV lower overpotential at 20 mA cm-2 in alkaline OER, respectively, than the nickel oxide. In particular, the addition of bismuth is especially influenced to intrinsic activity, the bismuth doped nickel oxide catalyst shows higher turnover frequency than the pristine nickel oxide although it has similar active surface area. Figure 1

Kinetic and Potential Modeling of the Electrolysis Cell for Nitrate Reduction Reaction to Ammonia

Electrochemical nitrate reduction reaction (NO3 -RR) is a potential renewable pathway to produce green ammonia. Excessive nitrate concentration in wastewater (>10 mg) threatens human health and contributes to eutrophication in agricultural applications. Furthermore, the burgeoning ammonia market, with an annual growth rate of USD 14.2 billion, necessitates green infrastructures to compete with the carbon-intensive Haber Bosch process with economic feasibility. The design of catalytic materials that aim to enhance the kinetics of nitrate reduction reactions is well-established in the literature. These catalytic materials present high catalyst activity, Faradaic efficiency (>90%), and durability for this reaction. The objective of our study is to conduct both computational study and eco-analysis to optimize the energy efficiency of the electrolysis system and evaluate its future economic potential. This can bridge the gap between the laboratory–scale electrolysis and industrial-scale units. In our modeling, we studied the effect of pH, membrane, conductivity, buffer solution, competing reactions, and kinetics of electrodes to find the potential losses and their origins in the electrolysis cell and calculate the final cell voltage for industrial applications. The primary sources of potential losses identified in these cells include Nernstian loss resulting from the pH difference between the boundary layer and bulk, ohmic loss due to solution resistance, and overpotentials required for activating the reaction. We established a computational platform for both laminar flows, where bubble evolution at the cathode and anode surfaces was not considered, and a bubbly flow model, which accounts for the effect of bubble evolution on liquid velocity and consequently pH distribution. The results of our study demonstrate close agreement with experimental findings. Figure 1

Investigation on Effect of Reducing Cathode Pt-Loading on Ohmic Overpotential in Catalyst Layer

To reduce the use of precious metals in polymer electrolyte fuel cells (PEFCs), it is necessary not only to develop high activity catalysts but also to design optimal membrane-electrode-assembly (MEA) structure. In the past two decades, it becomes well known that oxygen transport resistance near the catalyst surface is a critical issue when reducing cathode catalyst loading due to concentration of oxygen flux on a small catalyst surface area [1-3]. On the other hand, as well as the case of oxygen flux, small catalyst surface area also increases proton current density near the catalyst particles, which can cause larger overpotential due to proton migration (ohmic overpotential). This is likely to be more important for recent-trend catalyst layer structure which avoids direct coating of ionomer on the catalyst to improve catalyst activity, e.g., employing porous carbon for the catalyst support [4-5]. Such a structure of catalyst layer can cause large resistance especially at a low humidity condition where no proton conduction path through water film exists. In this study, we investigated the effect of reducing catalyst loading on ohmic overpotential in catalyst layers to discuss the impact of local proton resistance quantitatively.MEA samples were fabricated by a pulse spray method using commercial catalyst supported on porous carbon and solid carbon (TEC10E50E and TEC10V30E, TANAKA Kikinzoku Kogyo K.K.), respectively. Nafion D2020 was employed as an ionomer, and ionomer-carbon weight ratio (I/C) was varied. For each specification, MEAs with different Pt-loading on cathode were prepared with the value of ~0.05 mgPt/cm2 and ~0.2 mgPt/cm2, respectively. GORE-SELECT Membrane M788.12 was employed as a membrane. Humidity dependence of the cell performance was evaluated at a cell temperature of 80°C. To evaluate ohmic overpotential within the catalyst layer, the performance was evaluated varying oxygen partial pressure (p O2). Structures of catalyst layers were analyzed using a scanning electron microscope and a transmission electron microscope.Some of the evaluation results are shown below. Figure 1 shows the humidity dependence of the performance of the MEAs with different cathode catalyst loading at a high p O2 condition of 100 kPa, where the oxygen concentration overpotential can be ignored in a wide current density range. The performance of the low Pt-loading MEA shows large humidity dependence. One of the reasons of this is humidity dependence of the catalyst activity reflecting the humidity dependence of the electrochemical surface area. Additionally, the apparent Tafel slope is larger at lower humidity, which indicates the contribution of the ohmic overpotential at such a low current density. Figure 2 shows the performance at various p O2, where the current density is normalized by p O2. Assuming a reaction order equal to 1 for the oxygen reduction reaction, this p O2-normalized current should be identical at a certain electrode potential for the variation of p O2 when the proton resistance is enough small and spatial reaction-distribution within the catalyst layer can be assumed homogeneous. For the high humidity performance of solid carbon MEA presented in Fig. 2 (c), the p O2 normalized performance is almost identical for all the p O2 conditions, which supports that ohmic overpotential is not significant in this current density range. On the other hand, at the relative humidity of 40%, the normalized performance shows large deviations, which reflect the proton resistance contribution, for all of the samples. The low Pt-loading samples show relatively larger deviations, especially for the porous carbon MEA, which indicates the effect of the local proton resistance. Origin of these proton resistance will be discussed in conjunction with the structures of the catalyst support and catalyst layer.The results suggest that the local proton resistance in the vicinity of the catalyst particles causes overpotential large enough to suppress the cell performance. To investigate local proton transport character of developed catalyst, it should be useful to evaluate Pt-loading dependence of the ohmic overpotential.

Sowing Clean-Release Salt Catalyst for the Synthesis of Contamination-Free Single-walled Carbon Nanotube Arrays.

Horizontal arrays of single-walled carbon nanotubes (SWCNTs) have shown immense potential for application in emerging devices due to their excellent electrical and thermal properties. The direct growth of SWCNTarrays using high-activity metal catalysts is one of the promising methods to approach the mass production of dense SWCNT arrays. However, an inevitable obstacle lies in the post-purification of metal residual. Herein, a sowing strategy to prepare size-tunable potassium chloride (KCl) catalysts for the efficient growth of the SWCNT array with a density of 10 tubes per micron is reported. Through a controllable etching process, numerous surface defects (e.g., vacancies and kinks) are uniformly generated on the substrate as seed pit-like sites for the accommodation and anchoring of catalysts. The well-distributed KCl catalysts with a homogeneous size of ≈1.4nm enable the growth of ≈1.3nm SWCNTs through a vapor-liquid-solid mechanism. Importantly, 94 at.% KCl catalysts can be dramatically removed through a simple water-washing process, thus leaving contamination-free SWCNT arrays behind. Interestingly, 85% of nanotubes show metallic properties, which is demonstrated by the combination of electrical characterization and the multi-laser Raman spectroscopy. This sowing strategy contributes to the direct growth of uncontaminated high-density SWCNT arrays.

Microwave-absorbing property, chemical adsorption, and catalytic activity of monolithic LamMnnOx catalyst in microwave catalytic combustion of toluene

To verify the catalytic activity of LamMnnOx (m,n = 1,2; x = 2.5 ∼ 5.5) catalyst in microwave catalytic combustion of volatile organic compounds (VOCs), monolithic LamMnnOx catalysts were prepared and applied in toluene oxidation in this study. The research demonstrated that the LamMnnOx catalysts had strong microwave-absorbing properties due to first dielectric loss and secondary magnetic loss. The bed temperature rose rapidly due to the formation of hotspots under microwave irradiation. Furthermore, LamMnnOx catalysts chiefly adsorbed toluene by chemical adsorption, and the adsorption capacity of Mn was much stronger than that of La. Based on the activity tests, La1Mn1Ox (x = 2.5 ∼ 3.5) catalyst exhibited the highest catalytic activity among the four catalysts, and toluene was converted and mineralized completely at 259 ℃ and 315 ℃, respectively, under the conditions of an initial toluene concentration of 1000 mg/m3, bed height of 150 mm, and gas velocity of 2.5 L/min. Highly active LaMnO3 perovskite, uniform distribution of active particles, and abundant oxygen vacancies ensured the high activity of the La1Mn1Ox catalyst. Hence, the La1Mn1Ox catalyst was stable after a total of 600 min of activity test. According to electron transfers on the active Mn surface, the adsorption and activation of gaseous oxygen, and the transformation of Oads to Olatt on the oxygen vacancies, toluene oxidation speculates to follow the Langmuir-Hinshelwood and the Mars-van Krevelen mechanisms simultaneously. Therefore, this work provides further technological support for applying LamMnnOx catalysts in microwave catalytic combustion of industrial VOCs waste gas.

Engineering a novel interface structure on La0.75Sr0.25Cr0.5Mn0.5O3-δ-Gd0.1Ce0.9O2-δ fuel electrode with excellent electrochemical performance and sulfur tolerance for electrocatalytic CO2 reduction

Surface and interface engineering as an efficient and controllable strategy in designing electrode structure has been widely investigated for achieving high catalyst activity and durability of robust electrodes in solid oxide cells (SOCs). The constructed heterojunction structures favor expedited charge transfer and promote the catalytic reaction. Anti-coking La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM)-based fuel electrodes are considered as promising candidates for alternative Ni-based cermet electrodes in solid oxide electrolysis cell (SOEC), however, they suffer from insufficient electrocatalytic activity for CO2 electrolysis. Herein, Mn-containing Pr0.6Sr0.4FeO3-δ (Pr0.6Sr0.4Fe0.8Mn0.2O3-δ, PSFM) nanoparticles with excellent catalyst activity are synthesized and epitaxially grown on the surface of LSCM via infiltration technique. The spontaneous connected interface can provide direct tunnel for oxygen ion and electron transport along the (110) plane of LSCM. Meanwhile, this interface promotes an increase in oxygen vacancies and enhances both surface oxygen exchange and bulk oxygen diffusion capacities. These improvements are advantageous for CO2 adsorption and carbonate dissociation at three phase boundaries (TPBs), leading to a significant enhancement in the kinetics of CO2 reduction reaction. The electrolyte-supported single with PSFM/La0.75Sr0.25Cr0.5Mn0.5O3-δ-Gd0.1Ce0.9O2-δ (LSCM-GDC) fuel electrode exhibits an impressive current density of 1.09 A cm−2 at the applied voltage of 1.5 V and 800 °C, which increases by approximately 336 % than that of LSCM-GDC. In addition, the atomic arrangement enables in-situ formation of PSFM by trapping of surface Sr/Mn atoms on the LSCM surface, avoiding Sr segregation and enhancing the resistance to sulfur poisoning. This study demonstrates a strategy for achieving the enhanced CO2 electrolysis performance and sulfur tolerance by engineering highly active interface.

Molten-salt synthesis of highly condensed and nitrogen-tunable carbon nitride materials for metal-free and efficient synthesis of dimethyl carbonate

Dimethyl carbonate (DMC) is a building block in the modern chemical industry, and the transesterification of ethylene carbonate (EC) with methanol is a more sustainable strategy for the synthesis of DMC. Wherein, the design of metal-free and high-activity catalysts that can be easily prepared is a crucial research topic for clean synthesis of DMC. In this work, C3N4-T materials with non-metal components, high degrees of polycondensation, and adjustable distributions of nitrogen-containing species were successfully prepared by a facile molten-salt approach. Compared with g-C3N4 prepared by the traditional thermal polycondensation method, C3N4-T materials own larger specific surface areas and a higher degree of intralayer condensation. By simply adjusting the calcination temperatures, the fractions of bridging nitrogen species can be tuned, resulting in an improvement in alkaline strength. For the transesterification reaction of EC with methanol, the C3N4-500 materials demonstrated much higher activity than g-C3N4. Under a lower reaction temperature (100 °C) and a shorter reaction time (3 h), the maximum conversion of EC was 79.9 %. According to the characterization results of XPS and Hammett titration, the correlation between the catalytic activity of various C3N4-T materials and the alkaline properties was deliberated.

Role of perovskites phase in Ni-based catalysts for low temperature CO2 methanation

CO2 methanation is considered as a promising reaction in the context of mitigating climate change by reducing CO2 emissions and providing a renewable source of methane fuel. The CeNiO3 and LaNiO3 perovskite catalysts were synthesized using the sol-gel method. The effect of perovskite structure on the catalytic activity was studied. The results were compared with Ce-supported and La-supported Ni catalysts (Ni/CeO2 & Ni/La2O3). Different methods including XRD, N2 adsorption-desorption, H2-TPR, FE-SEM, and CO2-TPD, were employed for the characterization of the catalysts. The perovskite catalysts are more active than the corresponding supported catalysts. Among all prepared catalysts CeNiO3 perovskite catalyst showed highest activity 80% conversion and 98% selectivity at 300 °C. Weak basicity, high active metal reducibility and the synergy between Ni and Ce due to perovskite structure are the responsible factors for high activity of CeNiO3 catalyst. The CeNiO3 catalyst showed excellent stability for CO2 methanation during 24 h of time on study with different GHSVs. The effect of calcination temperature was also studied on CeNiO3 catalyst at 650, 750 and 850 °C temperatures. Raman spectra concluded that the oxygen vacancy sites increased with rise of calcination temperature from 650 to 750 °C and decreased with further increase in temperature. The CeNiO3 calcined at 750 °C (CeNiO3-750) showed highest activity among all other catalysts. The increased activity is due to increased oxygen vacancies which ensures that Ni nanoparticles are highly dispersed.

Recent Advances in NO Reduction with NH3 and CO Over Cu-Ce Bimetallic and Derived Catalysts

Sintering flue gas contains significant amounts of harmful gases, such as carbon monoxide and nitrogen oxides (NOx), which pose severe threats to the ecological environment and human health. Selective catalytic reduction (SCR) technology is widely employed for the removal of nitrogen oxides, with copper-cerium-based bimetallic catalysts and their derivatives demonstrating excellent catalytic efficiency in SCR reactions, primarily due to the significant synergistic effect between copper and cerium. This paper summarizes the main factors affecting the catalytic performance of Cu-Ce-based bimetallic catalysts and their derivatives in the selective catalytic reduction of ammonia and carbon monoxide. Key considerations include various preparation methods, doping of active components, and the effects of loading catalysts on different supports. This paper also analyzes the influence of surface oxygen vacancies, redox capacity, acidity, and specific surface area on catalytic performance. Additionally, the anti-poisoning performance and reaction mechanisms of the catalysts are discussed. Finally, the paper proposes strategies for designing high-activity and high-stability catalysts, considering the development prospects and challenges of Cu-Ce-based bimetallic catalysts and their derivatives, with the aim of providing theoretical guidance for optimizing Cu-Ce-based catalysts and promoting their industrial applications.

Selective Hydrogenation of Furfural Under Mild Conditions Over Single-Atom Pd1/α-MoC Catalyst.

The selective activation of C=O bonds was the key challenge in the field of biomass utilization. Researchers worked on this purpose by developing high-active and high-selective catalysts. In this study, a Pd1/α-MoC single-atom catalyst was synthesized and applied in selective hydrogenation of biomass-derived furfural with 96.7 % conversion and 92.4 % selectivity under a near-room temperature. With various characterizations, the formation of Pd single-atom sites over the surface of α-MoC was confirmed. Then, the dominant structure of Pd single-atom site and the reaction pathway were proposed with experimental and Density Functional Theory (DFT) studies. Compared with undecorated α-MoC, the introduction of Pd single-atom species significantly altered the reaction mechanism from Meerwein-Ponndorf-Verley (MPV) process. Moreover, the Pd single-atoms loading on α-MoC(111) surface notably reduced the energy barriers of H2 activation and C=O bond hydrogenation, which may lead to the improving catalytic performance of α-MoC based catalyst. Hence, this investigation could provide a new strategy and understanding for the development of high-active and low-cost catalysts.

Single-Pass Demonstration of Integrated Capture and Catalytic Conversion of CO2 from Simulated Flue Gas to Methanol in a Water-Lean Carbon Capture Solvent.

Here, we demonstrate an integrated semibatch simultaneous CO2 capture and conversion to methanol process using a water-lean solvent, N-(2-ethoxyethyl)-3-morpholinopropan-1-amine (2-EEMPA), that serves as both the capture solvent and subsequent condensed-phase medium for the catalytic hydrogenation of CO2. CO2 is captured from simulated coal-derived flue gas at a target >90 mol % capture efficiency, with a continuous slipstream of CO2-rich solvent delivered to a fixed bed catalytic reactor for catalytic hydrogenation. A single-pass conversion rate >60 C-mol % and selectivity >80 C-mol % are observed for methanol at relatively low temperatures (<200 °C) in the condensed phase of the carbon capture solvent. Hydrogenation products also include higher alcohols (e.g., ethanol and propanol) and hydrocarbons (e.g., methane and ethane), suggesting that multiple products could be made offering adaptability with varied CO2-derived products. Catalyst activity and selectivity are directly impacted by the water content in the capture solvent. Anhydrous operation provides high catalyst activity and productivity, suggesting that water management will be a critical parameter in real-world operation. Ultimately, we conclude that the integrated capture and catalytic hydrogenation of CO2 are chemically viable and potentially more energetically efficient and cost-effective than conventional separate capture and conversion approaches.

Low-vanadium and high-activity SCR catalyst for low-temperature denitrification: Influence of vanadium precursor and surface vanadium concentration

Nitrogen oxides (NOx), as the main pollutants of air pollution, cause serious harm to the ecological environment and human health. SCR technology is widely used as the most effective method for treating NOx. The core of SCR technology is SCR catalyst. The reaction temperature of traditional commercial catalysts is difficult to reach the optimal operating temperature range, so expanding the temperature window of V2O5/TiO2 catalysts to the low-temperature region while reducing vanadium loading is a key issue to be solved. A series of V2O5/TiO2 catalysts with different vanadium precursors and different vanadium loadings were prepared by solid-phase synthesis method. The physicochemical properties of the catalyst were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, temperature programmed desorption of ammonia and temperature programmed reduction of hydrogen. The denitrification activity of the catalyst was evaluated in a fixed bed reactor. The catalysts prepared with vanadyl oxalate (VOC2O4·xH2O) and vanadyl acetylacetonate (VO(acac)2) as vanadium precursors with a vanadium loading of 5% exhibited the highest denitrification activity, with a stable NOx conversion of 100% within the temperature range of 200–350 °. Compared with the catalysts prepared with ammonium metavanadate (NH4VO3) and vanadyl sulfate (VOSO4·xH2O) as the vanadium precursors, the maximum activity temperature of VOC2O4-V5Ti and VO(acac)2-V5Ti shifted towards the low-temperature region by about 150 °. Furthermore, the denitrification activity of catalyst with a low vanadium content (1%) prepared using VO(acac)2 precursor was even higher than that of catalyst with a high vanadium content (6%) prepared using NH4VO3 precursor. Using VOC2O4 and VO(acac)2 as vanadium precursors could effectively regulate the active sites and polymeric states on the catalysts, and promote the interaction of V atoms with different valence states to form more reductive V species (V4+), thus exhibiting excellent SCR reactivity. This study provided an effective method for the preparation of low-vanadium and high-activity denitrification catalysts at low temperatures.

The electrochemical synthesis of urea on triatomic cluster/Cu catalysts: A theoretical study

Urea (NH2CONH2), a crucial nitrogen fertilizer and industrial raw material, is typically synthesized under rigorous reaction conditions. Currently, the electrocatalytic transformation of N2 and CO2 into urea is a promising strategy. However, finding a high-selectivity and high-activity catalyst remains a significant challenge. Herein, the activity of a series of transition metal clusters (VIII and IB groups) on copper-based catalysts for electrochemical coupling of CO2 and N2 has been systematically studied to produce urea via density functional theory (DFT). Most catalysts exhibit good thermodynamic stability and accomplish co-adsorb CO2 and N2. Notably, Fe3 and Ni3/Cu100 catalysts achieve C-N coupling via *CO and *N2, whereas Ru3, Rh3, Os3, and Ir3/Cu100 catalysts accomplish C-N coupling via *CO and *NHNH. Among all catalysts, the Ni3/Cu100 catalyst features excellent catalytic activity with a rate-determining step as low as 0.480 eV, and its C-N coupling only needs to overcome a barrier of 0.844 eV. Additionally, the Ni3/Cu100 catalyst can effectively inhibit the hydrogen evolution reaction (HER), further protonation of *CO and ammonia formation, thereby ensuring high selectivity for urea. Electronic structures analysis further reveals an “acceptance-donation” mechanism for the activation of *CO2 and *N2, with the introduction of the Ni3 cluster showing a decisive role. Therefore, this study may establish the foundation for the electrochemical synthesis of urea.

Gold Catalysts for Selective Hydrogenations: The Role of Heterolytic H2 Dissociation

AbstractHydrogenations are fundamental transformations in organic synthesis, and the industrial applications span from food, petrochemical, fine chemicals to pharmaceuticals synthesis where hydrogenations of multifunctional molecules should be carried out in a chemoselective way. In this concept article we aim at providing an overview on the activation of molecular hydrogen (H2) via heterolytic dissociation, which is responsible to unlock high activity of gold catalysts for chemoselective hydrogenations. The key benefit of heterolytically dissociated H species is their preference for hydrogenating polar unsaturated groups like C=O, C=N, and C=S, as these polar bonds are ideal acceptors for proton and hydride pairs. We will provide examples on how to obtain enhanced chemoselectivity on alkynes, α, β‐unsaturated aldehydes and nitro‐compounds hydrogenations with gold catalysts.

A review of ordered PtCo3 catalyst with higher oxygen reduction reaction activity in proton exchange membrane fuel cells

This review is devoted to the potential advantages of ordered alloy catalysts in proton exchange membrane fuel cells (PEMFCs), specifically focusing on the development of the low Pt content, high activity, and durability ordered PtCo3 catalyst. Due to the sluggish oxygen reduction reaction (ORR) kinetics and poor durability, the overall performance of the fuel cell is affected, and its application and promotion are limited. To address this issue, researchers have explored various synthetic strategies, such as element doping, morphology adjusting, structure controlling, ordering and support/metal interaction enhancement. This article extensively discussed the Pt related ORR catalysts and follows an in-depth analysis of ordered PtCo3. The introduction briefly discusses the direction of development of fuel cell catalysts and frontier progress, including theoretical mechanism, practical preparation, and Pt-containing electrode structures, etc. The subsequent chapter focuses on the Pt-Co catalyst, the evolution process of Pt alloy to Pt-Co alloy and the improvement scheme are introduced. The next chapter describes the properties of PtCo3. Although the ordered PtCo3 catalyst has a wide range of applicability due to low cost and high activity catalyst. However, besides the common agglomeration and sintering problems of Pt-Co alloy, its commercial application still faces unique problems of oversized crystal size, phase segregation, ordering transformation and transition metal dissolution. Therefore, in Chapter 4, this overview provides some possible improvement methods for three specific functions: crystal refinement, enhancing the effect of support and active substances, and anti-dissolution.

New insights into the catalyst and cocatalyst pre‐contact process in ethylene copolymerization

AbstractThe influence of pre‐contacting time and temperature as well as mixing intensity on polyethylene copolymerization has been investigated employing DSC, rotational rheometry tests, as well as particle size distribution analysis. For this purpose, a commercial‐supported Ziegler–Natta catalyst has been pre‐contacted with Teal as cocatalyst under different time, temperature, and stirring speed followed by similar polymerization process. It was found that the increase in mixing intensity has no impact on rheological properties; it causes increase in crystallinity percentage of polymer due to better distribution of active centers. Moreover, the pre‐contacting time represents the most impact on catalyst activity and rheology of polymer powder while the pre‐contacting temperature changes is mostly effective on controlling the morphology of polymer. Additionally, the results reveal that 10‐min pre‐contacting of catalyst and Teal under 10°C and stirring speed of 500 rpm was accompanied by highest catalyst activity and lowest content of fine particles.Highlights Pre‐activation was studied under different time and temperature. Adjusting pre‐contacting time influences the polymer morphology. Pre‐contacting under lower temperature results in narrower molecular weight distribution.

P-Block Aluminum Single-Atom Catalyst for Electrocatalytic CO2 Reduction with High Intrinsic Activity.

Atomically dispersed transition metal sites on nitrogen-doped carbon catalysts hold great potential for the electrochemical CO2 reduction reaction (CO2RR) to CO due to their encouraging selectivity. However, their intrinsic activity is restricted by the hurdle of the high energy barrier of either *COOH formation or *CO desorption due to the scaling relationship. Herein, we discover a p-block aluminum single-atom catalyst (Al-NC) featuring an Al-N4 site that enables disentangling this hurdle, which endows a moderate reaction kinetic barrier for *COOH formation and *CO desorption, as validated by in situ attenuated total reflection infrared spectroscopy and theoretical simulations. As a result, the developed Al-NC shows a CO Faradaic efficiency (FECO) of up to 98.76% at -0.65 V vs RHE and an intrinsic catalytic turnover frequency of 3.60 s-1 at -0.99 V vs RHE, exceeding those of the state-of-the-art Ni-NC and Fe-NC counterparts. Moreover, it also delivers a partial CO current of 309 mA·cm-2 at 93.65% FECO and 605 mA at >85% FECO in a flow cell and membrane electrode assembly (MEA), respectively. Strikingly, when using low-concentration CO2 (30%) as the feedstock, this catalyst can still deliver a partial CO current of 240 mA at >80% FECO in the MEA. Considering the earth-abundant character of the Al element and the high intrinsic activity of the Al-NC catalyst, it is a promising alternative to today's transition metal-based single-atom catalysts.