Distribution Of Active Sites Research Articles

Degradation of Rhodamine B dye using the mesoporous material KIT-6/TiO2 photocatalyst obtained by in situ anchoring method.

In this study, a novel synthesis approach was employed to create the KIT-6/TiO2 photocatalyst with different ratios of Si/Ti. The results of the X-ray diffraction revealed that incorporating TiO2 with the anatase phase maintained the mesoporous structure of KIT-6 (Korean Institute of Technology 6). The scanning electron microscope and transmission electron microscope images exhibited unobstructed mesopores, validating their anchoring within the internal structure of the support. Furthermore, nitrogen adsorption-desorption studies confirmed the presence of TiO2 within the pores. X-ray photoelectron spectroscopy (XPS) analysis corroborated the successful incorporation of TiO2, showing the presence of Ti4+ and Ti3+ species, with Ti3+ indicating the presence of oxygen vacancies that enhance photocatalytic performance. Photodegradation efficiency was assessed for Rhodamine B, achieving 95% and 86.5% for KIT-6/TiO2 (Si/Ti = 25) and KIT-6/TiO2 (Si/Ti = 75), respectively. The molar ratio Si/Ti = 25 exhibited higher activity, which can be attributed to a better distribution of active sites, as confirmed by the measurement of turnover frequency (TOF = 2.0 × 10-2min-1). The stability of the KIT-6/TiO2 (Si/Ti = 25) has also been investigated, and stable performance in recycling photocatalytic reactions was obtained after four cycles of use. The scavengers used indicated that the superoxide anion radical (•O2-) and electron (e-) were the major active species. This study successfully demonstrated the incorporation of TiO2 into the walls of mesoporous materials using the ISA method, achieving high photocatalytic efficiency. Moreover, this method enabled superior performance with a reduced amount of photocatalyst compared to a pure TiO2 sample.

Biomimetic Construction of Ferriporphyrin‐Based Porous Catalysts for Boosting Nitrogen Electroxidation to Nitrate

AbstractElectrocatalytic N2 oxidation reaction (NOR) is an environmentally sustainable approach to synthesize NO3− under mild conditions. Inspired by the ferriporphyrin (FePP) catalytic species in nitrite oxidoreductase, three FePP‐based biomimetic catalysts with different functional groups (─NH2, ─H, and ─COOCH3) are designed and prepared successfully. Theoretical calculations indicate that these functional groups can alter the electron density of Fe catalytic center, affecting their ability to adsorb and activate N2. The strong electron‐donating ability of ─NH2 group can enhance the electron density of iron sites, which reveals a maximum NO3− yield of 728.55 µmol h−1 gFePP−1 and a high Faradaic efficiency of 10.6%. After that, the optimized FePP molecules can be encapsulated into ZIF‐8, which remarkably promoted the N2─to─NO3− transformation with a NO3− production rate of 1767.74 µmol h−1 gFePP−1, achieving the highest catalytic effect among metalloporphyrin‐based molecular catalysts under mild conditions. This work develops an available biomimetic approach to modulate the electron distribution of active metal sites and confine catalytic species into porous crystalline materials for constructing high‐performance NOR electrocatalysts.

Resolving the Nanostructure of Carbon Nitride-Supported Single-Atom Catalysts.

Single-atom catalysts (SACs) are gathering significant attention in chemistry due to their unique properties, offering uniform active site distribution and enhanced selectivity. However, their precise structure often remains unclear, with multiple models proposed in the literature. Understanding the coordination environment of the active site at the atomic level is crucial for explaining catalytic activity. Here, a comprehensive study of SACs made of carbon nitride (CNx) containing isolated nickel atoms is presented. Using a combination of synthesis techniques and characterization methods including Fourier-transform infrared spectroscopy, X-ray absorption spectroscopy (XAS), and density functional theory (DFT) calculations, the local environment of nickel active centers in CNx-supported SACs is investigated. These results challenge conventional structural models and propose a new architecture that better aligns with current experimental evidence. This new structure serves as a foundational step toward a rational approach to catalyst development and can facilitate more precise design and application of these innovative catalysts.

The effect of carbon supports on the electrocatalytic performance of Ni-N-C catalysts for CO2 reduction to CO

Carbon-supported nickel and nitrogen co-doped (Ni-N-C) catalysts have been extensively studied as selective and active catalysts for CO2 electroreduction to CO. Most studies have focused on adjusting the coordination structure of Ni-Nx active sites, while the impact of the carbon supports has often been overlooked. In this study, a series of Ni-N-C catalysts on different carbon supports, including carbon black (CB), multi-walled carbon nanotubes (CNT), and activated nitrogen-doped biochar (ANBC), were synthesized using a ligand-mediated method. The effect of the carbon support on the electrocatalytic performance for CO2 reduction was investigated at both low current densities, in a H-cell, and high current densities, in a MEA electrolyzer. All of the prepared Ni-N-C catalysts show good faradaic efficiencies (FE) toward CO production (up to ~90%), however, the onset potentials and partial current densities for CO production vary greatly. The textural properties of the carbon support and the distribution of Ni-Nx active sites on the carbon support are demonstrated as the main factors behind the performance differences. In particular, hierarchical porous structures with large specific surface area are helpful to facilitate mass transport and improve the dispersion of active sites, which allows for a better CO2 reduction performance of Ni-N-ANBC compared to Ni-N-CB and Ni-N-CNT. This study demonstrates the importance of the carbon support for Ni-N-C catalysts and provides new insights into the design of efficient Ni-N-C catalysts for the CO2RR.

Atomic-Level Engineering of Single Ag1+ Sites Distribution on Titanium-Oxo Cluster Surface to Boost CO2 Electroreduction

Precise control over the distribution of active metal sites on catalyst surfaces is essential for maximizing catalytic efficiency. Addressing the limitations of traditional cluster catalysts with core-embedded catalytic sites, this...

The Synthesis, Characteristics, and Application of Hierarchical Porous Materials in Carbon Dioxide Reduction Reactions

The reduction of carbon dioxide to valuable chemical products could favor the establishment of a sustainable carbon cycle, which has attracted much attention in recent years. Developing efficient catalysts plays a vital role in the carbon dioxide reduction reaction (CO2RR) process, but with great challenges in achieving a uniform distribution of catalytic active sites and rapid mass transfer properties. Hierarchical porous materials with a porous hierarchy show great promise for application in CO2RRs owing to the high specific surface area and superior porous connection. Plenty of breakthroughs in recent CO2RR studies have been recently achieved regarding hierarchical porous materials, indicating that a summary of hierarchical porous materials for carbon dioxide reduction reactions is highly desired and significant. In this paper, we summarize the recent breakthroughs of hierarchical porous materials in CO2RRs, including classical synthesis methods, advanced characterization technologies, and novel CO2RR strategies. Moreover, by highlighting several significant works, the advantages of hierarchical porous materials for CO2RRs are analyzed and revealed. Additionally, a perspective on hierarchical porous materials for CO2RRs (e.g., challenges, potential catalysts, promising strategies, etc.) for future study is also presented. It can be anticipated that this comprehensive review will provide valuable insights for further developing efficient alternative hierarchical porous catalysts for CO2 reduction reactions.

The CoNi@C/Mo1.33C i-MXene Derived from Novel (Mo2/3R1/3)2GaC (R = Dy, Ho, Er, Tm, and Lu) Nanolaminations for Electrochemical Application in Electrocatalytic Hydrogen Evolution and Supercapacitance.

2D Mo1.33C i-MXene is highly promising for electrochemical applications. Here, a synthetic strategy is reported, enabling the uniform distribution of carbon-coated CoNi (CoNi@C) nanoparticles on the vacancy-ordered Mo1.33C i-MXene nanosheets, thereby fully exposing the active sites of CoNi@C. First, five novel Ga-containing (Mo2/3R1/3)2GaC (R = Dy, Ho, Er, Tm, and Lu) i-MAX phases are synthesized as the precursor and found to be crystallized into Cmcm structure, followed by hydrothermal etching and delamination. Subsequently, CoNi- MOF is in situ grown on derived Mo1.33C i-MXene nanosheets. By modifying the loading mass and annealing condition, CoNi-MOF is transformed into the CoNi@C and the CoNi@C/Mo1.33C displayed outstanding hydrogen evolution reaction activity with low overpotential (73mV at 10 mA cm-2) and small Tafel slope (84 mV dec-1). Moreover, the gravimetric capacitance is also increased from 68 F g-1 in CoNi@C to 575.1 F g-1 in CoNi@C/Mo1.33C-50 at 0.5 A g-1. After ≈5000 cycles, activation is complete, and the specific capacitance reaches its maximum value. Additionally, the specific capacitance remains stable at 95% after additional 10000 cycles. This work improves the catalytic and supercapacitor performance of composite nanomaterials by optimizing the distribution of active sites on Mo1.33C i-MXene, and also extends the application of Mo1.33C i-MXene.

Room Temperature Synthesis of Gradient-Distributed Ni/Fe Sites in Layered Double Hydroxides for Enhanced Oxygen Evolution Reaction.

NiFe-based materials, especially NiFe layered double hydroxides (LDHs), are recognized as the most promising non-precious metal electrocatalysts for alkaline oxygen evolution reaction (OER). However, the precisely designed distribution of active sites for enhancing activities is still significantly restricted due to the lack of reasonable modulation strategies. Herein, sulfur doped Ni/Fe gradient-distributed LDH (GD-NiFe LDH/S) is fabricated by facile air-induced strategy at room temperature. This strategy accelerates the growth process with abundant CO2 and O2 in air, which promotes the inward migration of Fe species, resulting in gradient distribution with Ni/Fe-rich edge/planar. This allows significant enhancement of Ni/Fe synergistic effect, which plays a vital role in OER. Moreover, the sharp pine-like morphology of GD-NiFe LDH/S endows superhydrophilicity/aerophobicity characteristics, facilitating electrolyte penetrating and oxygen releasing. The optimized GD-NiFe LDH/S delivers superior OER performance with low overpotentials of 234 and 270mV at 10 and 100mA cm-2. The assembled anion exchange membrane water electrolyzer only requires 1.90V at 1.0 A cm-2 and 2.10V at 1.5 A cm-2 with robust stability for at least 130 h. This work introduces a facile air-induced strategy under room temperature to controllably design active site distributions of LDH for enhanced OER performance.

Enhancing NH3-SCR denitrification performance through synergistic A- and B-site effects via CeFe modification of LaMnO3

ABO3 type perovskite catalysts are widely used in NH3-SCR to remove NOx due to excellent low-temperature reduction performance. To study the synergistic effect of A and B sites on the structure, morphology and redox performance of modified perovskite catalysts (La1-xCexMn1-yFeyO3), LaMnO3 perovskite catalysts were co-doped with CeFe by sol-gel method, and the crystal structure, surface chemical environment, optimal metal co-doping ratio and surface adsorption of the modified perovskite catalysts were clarified through various characterizations. In addition, through first-principles calculations, the differential charge density and binding energy of each doping system were analyzed, the relationship between the difficulty of Ce doping and the electronic population of Mn atoms and the redox ability of the catalyst was discussed, and the key bond types and their changing rules in perovskite catalytic reduction were clarified. The results showed that co-doping Ce and Fe could improve the denitrification efficiency and sulfur resistance of the catalyst. When the Fe doping ratio is 0.1, the denitrification activity is the highest. Among them, the La0.9Ce0.1Mn0.9Fe0.1O3 catalyst showed the most favorable active acid site distribution and the best reduction performance, which was conducive to the adsorption and redox of gas molecules on the catalyst surface. At the same time, when the A and B sites were co-doped, the electron transferred mainly occurs between Ce ions and Fe ions, forming a synergistic effect and changing the covalent components between Mn-O and Fe-O bonds. This made the valence states of Mn and Fe ions more, enhanced the catalytic activity of perovskite, and promoted the redox of NO on the catalyst surface, thus providing a new idea for the redox reaction pathway of modified perovskite catalysts.

Novel mercury adsorption mechanism with bimetallic synergistic Se site: CuInSe2 for mercury fixation with wide temperature range from coal-fired flue gas

Mercury emissions from coal-fired power plants pose a significant threat to both the environment and human health. In this work, a novel CuInSe2 adsorbent with active selenium sites was synthesized for the removal of gaseous Hg0 during deep flue gas purification. This adsorbent serves as a bridge to establish the intrinsic connection between the new adsorption mechanism and mercury removal via bimetallic synergistic catalytic sites. By innovatively calculating the adsorption kinetics of the bimetallic selenide, along with XPS analysis and thermodynamic calculations, the reaction pathway of Hg0 on the surface of CuInSe2 and the proposed adsorption mechanism were validated. Additionally, the stable formation of HgSe on the lattice surface was confirmed. Characterization techniques such as SEM, TEM, and BET revealed the microscopic flower-like structure of CuInSe2 and confirmed the uniform distribution of active selenium sites. Experimental results demonstrate that CuInSe2 achieves nearly 100 % removal efficiency in the temperature range of 80–200 °C, and even after 6 hours of continuous operation, it maintains a removal rate of 96.49 %, showcasing excellent stability. Furthermore, due to its unique structural features, CuInSe2 exhibits strong resistance to interference from SO2 and NO, with an equilibrium adsorption capacity of 18.855 mg/g, surpassing most currently studied demercuration adsorbents. This makes CuInSe2 a highly promising material for mercury removal and provides an important reference for the development of selenium-rich site adsorbents.

Surface-Limited Electrochemical Reactions for the Characterization of Mass Transport in Nanoporous Electrodes

Minimizing transport losses in (nano)porous electrodes is essential to many electrochemical applications such as electrolyzers, fuel cells, high-power density batteries. Often diffusion is the dominating mechanism that limits mass transport in these electrodes with very large surface areas. Electrochemical methods that characterize diffusion in porous electrodes, such as electrochemical impedance spectroscopy and scanning electrochemical microscopy, are limited in their use due to complex data interpretation and/or stringent infrastructure requirements. We have developed a novel method that utilizes a surface-limited reaction in a rotating disk setup that allows for the fast and straightforward characterization of effective diffusion coefficients in nanoporous electrodes, as well as estimation of their roughness.Surface-limited electrochemical reactions, such as underpotential deposition (UPD), are commonly used to characterize the electrochemical surface area of porous electrodes. However, it has been shown that in nanoporous electrodes these processes can run into mass transport limitations, taking minutes to reach completion1,2. We utilize this effect in a rotating disk electrode setup, where it results in a characteristic current transient (Fig. 1a). An analytical model was developed to describe these current transients and extract performance parameters. Different sections of the current transient can be utilized to gain information on the porous electrode as illustrated in Fig. 1a. Besides the effective diffusion coefficient, determining the roughness of the porous electrode, the uniformity of the external mass transport resistance, and the bulk diffusion coefficient are possible. The tortuosity can then be determined from the bulk diffusion coefficient, porosity, and the effective diffusion coefficient. Further analysis of the analytical model also shows the possibility of electrochemically mapping the distribution of active sites in porous electrodes.The methodology was tested experimentally on a platinum nanomesh electrode3 utilizing Cu UPD. An SEM image of a cross-section of the electrode is given in Fig. 1b. The nanomesh electrode's intrinsic high volumetric surface area (~ 30 m²/cm³) leads for certain to mass transport limitations for the Cu UPD process even for Cu2+ concentrations up to 0.8 mol/L. This combined with the uniformity of the electrode thickness allows it to be the ideal model system to verify the analytical model. The methodology was validated for different reaction conditions by comparing the tortuosity which was found to remain constant. The applicability of our method to porous electrodes in general will be discussed. References Y. Liu, S. Bliznakov, and N. Dimitrov, J. Phys. Chem. C, 113, 12362–12372 (2009).E. E. Levin et al., Nanomaterials, 13 (2023).S. P. Zankowski and P. M. Vereecken, ACS applied materials & interfaces, 10, 44634–44644 (2018). Figure 1

Catalyst pellets with Gaussian activity distribution under forced periodic operation for reactions with Langmuir-Hinshelwood kinetics

This research investigates how combining forced periodic operation with spatially distributed catalyst activity can enhance heterogeneous catalytic processes. It focuses on analyzing reaction-diffusion phenomena within porous catalyst pellets. These pellets exhibit a Gaussian distribution of active sites, and the study investigates how externally forced periodic variations in bulk reactant concentration and temperature affect the reaction process. The paper establishes a mathematical model for a non-isothermal reaction based on Langmuir-Hinshelwood kinetics. This model is then transformed into its dimensionless form for numerical analysis. Numerical simulations are employed to investigate the impact of various parameters on the concentration and temperature profiles within the pellet, as well as on the pellet productivity. These parameters include the position and width of the Gaussian distribution of active sites, the Thiele modulus, the mass and heat Biot numbers, the Arrhenius number for reaction, the energy generation function, the ratio of characteristic times for diffusion and heat conductivity, and frequencies and amplitudes of periodic variations. The simulations reveal complex relationships between the spatial and temporal profiles of concentration and temperature within the pellets. Using porous granules with a non-uniform catalyst activity profile alongside forced periodic operations for reaction-diffusion processes enables higher productivity compared to granules with a uniform activity profile and subject to the steady-state operation. This study demonstrates the potential for optimizing catalytic processes in porous pellets with non-uniform activity profiles under forced periodic operation, offering valuable insights into enhancing process efficiency.

Transition Metals Doped into g-C3N4 via N,O Coordination as Efficient Electrocatalysts for the Carbon Dioxide Reduction Reaction.

The electrochemical carbon dioxide reduction reaction (CO2RR) is a potential and efficient method that can directly convert CO2 into high-value-added chemicals under mild conditions. Owing to the exceptionally high activation barriers of CO2, catalysts play a pivotal role in CO2RR. In this study, the transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) is doped into g-C3N4 with a unique N,O-coordination environment, namely, TM-N1O2/g-C3N4. Herein, the catalytic performance and reaction mechanism for the CO2RR on TM-N1O2/g-C3N4 are systematically investigated by density functional theory methods. Especially, through the calculation of ΔG*H and ΔG*COOH/ΔG*OCHO, the catalysts with preference for the CO2RR over the hydrogen evolution reaction (HER) are selected for further study. Furthermore, Gibbs free energy computation results of each elementary step for the CO2RR on these catalysts indicate that Ti-N1O2/g-C3N4 has significant catalytic activity and selectivity for reducing CO2 to methanol (CH3OH) with the limiting potential (UL) of -0.55 V. Finally, through frontier molecular orbital theory and charge transfer analyses, the introduction of the O atoms illustrates that it is instrumental in regulating the electron distribution of the catalytic active site, thereby improving the catalytic performance. This work provides insight into the design of single-atom catalysts with unique coordination structures for the CO2RR.

Novel application of Ru-based catalysts on MgAl oxides alkaline adsorbents for cyclic CO2 methanation

This study explores the performances of Ru-based catalysts with a low metal content (2 wt%) supported on MgO and Mg-Al Oxides (MgAl) for cyclic CO2 adsorption and methanation at atmospheric pressure. Adsorption and desorption tests demonstrated that MgAl-based catalysts are more promising for CO2 capture due to their larger surface area and better distribution of active sites (Mg2+–O2-). Moreover, doping the MgAl support with K2CO3 further improves surface alkalinity and, consequently, capture performance. During cyclic operations, all the catalysts proved effective and selective for methane production. To simulate realistic conditions, both dry and wet CO2 adsorptions were conducted before the methanation stage. The presence of moisture positively influenced gas carbonation for all catalysts, increasing the overall amount of CO2 captured. Specifically, Ru/MgAl exhibited the best performance in terms of adsorption and conversion to methane (approximately 85 % after dry adsorption and 79 % after wet adsorption), with a maximum methane production of 183 and 220 μmolCH4 g−1, respectively. The reaction yield was further enhanced with Ru-K/MgAl, achieving 327 μmolCH4 g−1 after dry adsorption and 333 μmolCH4 g−1 after wet adsorption. However, this catalyst displays different conversion kinetics, attributed to slowed carbonate migration, low Ru dispersion, limited specific surface area, and excessive carbonation strength. Operando FTIR tests revealed differences in reaction intermediates between Ru/MgAl and Ru-K/MgAl, by going deeper into the kinetic differences observed. The study concludes that Ru/MgAl materials are highly promising catalysts for CO2 adsorption and methane production, supporting the development of technologies for CO2 abatement and renewable energy utilisation.

Boosting hydroisomerization of n-hexadecane by designing core-shell bifunctional catalysts with partially blocked micropores

Hydroisomerization of long-chain n-alkanes is an indispensable route for upgrading fossil fuels and lubricant oils to meet the state of art regulations. Precisely regulate the distribution of acidic and metal active sites to suppress unwanted cracking reaction is hitherto a difficult task. In this work, we develop a simple coating-carbonation strategy for constructing novel core-shell bifunctional catalysts, comprising ZSM-22 zeolite core with the partially blocked channels and Pt nanoparticles loaded on the mesoporous SiO2 shell. The unique treatment not only adjusted the distribution of acid sites located within the micropore channels and external surface, but also alter the locations and dispersion of Pt nanoparticles. Owing to the short diffusion lengths, nanoscale distance between acid sites and Pt species, and high metal dispersions, the core-shell bifunctional catalyst exhibits outperformed performance in n-hexadecane hydroisomerization, i.e., the yield of isomerized hexadecane can reach 87.9 %, which is among the relatively high level compared with the previous reported Pt/zeolite counterparts. Moreover, the catalyst also displays excellent stability (no deactivation within 100 h). The disclosed structure-catalysis relationship provides rational reference for designing the synergistic meta-acid active sites in the hydroisomerization of long-chain n-alkanes.

In-situ grown α-MoO3 hollow microspheres achieve high-sensitivity detection of trimethylamine

The direct in-situ growth synthesis method not only ensures a uniform thin layer and an optimized distribution of active sites but also significantly enhances gas adsorption and electron transfer efficiency. In this research, α-MoO3 hollow microspheres were successfully grown in-situ on a ceramic tube using a solvothermal method and applied to the highly sensitive detection of triethylamine (TEA). The α-MoO3 hollow microspheres, due to their unique nanostructure and optimized morphological characteristics, exhibited a high response of 90.965–50 ppm TEA at the optimal operating temperature of 217 °C, along with an ultra-low detection limit of 0.1 ppm. The sensitivity mechanism of α-MoO3 to TEA was deeply revealed through characterization techniques such as X-ray photoelectron spectroscopy (XPS), confirming its high selectivity in gas detection. Moreover, the sensor demonstrated excellent reliability in a long-term stability test over 180 days, providing a high-performance detection method for environmental monitoring and industrial safety fields. This research not only contributes a new perspective to the development of TEA detection technology but also provides important experimental evidence and theoretical support for the design and preparation of high-sensitivity gas sensors based on α-MoO3.

Modular hydrogel selectively adsorbs phosphates and hexavalent chromium while enabling phosphate recovery

Electroplating wastewater containing high concentrations of phosphates and hexavalent chromium Cr(VI) poses serious environmental pollution. Moreover, phosphorus, as a non-renewable resource, necessitates its recovery to meet sustainable development goals. To address this issue, this study used sodium alginate as the scaffold module, synthesized lanthanum carbonate in situ within a chitosan module to serve as the phosphate adsorption module, and employed polyethyleneimine (PEI) modules to enhance the adsorption capacity for Cr(VI), successfully fabricating a modular hydrogel (LC-CSP). LC-CSP exhibits a complex porous structure and surface morphology, forming an ultra-low-density fiber network with good strength and elasticity, ensuring uniform distribution and exposure of active sites. Under optimal conditions for single-component adsorption, LC-CSP achieved adsorption capacities of 232.02 mg/g for phosphates and 474.61 mg/g for Cr(VI). Additionally, LC-CSP demonstrated excellent reusability, retaining over 83 % of its performance after five cycles. In simulated electroplating wastewater experiments with various interfering substances, LC-CSP maintained high removal efficiencies (>90.72 %) for phosphates and Cr(VI). Post-experiment, enriched water after phosphate desorption was further treated to recover phosphorus resources in complex water environments. Multiple characterization techniques elucidated the adsorption mechanisms of LC-CSP: phosphate adsorption primarily involved ligand exchange, electrostatic interactions, and hydrogen bonding, while Cr(VI) adsorption included electrostatic interactions, hydrogen bonding, and reduction reactions. Finally, fixed-bed simulated wastewater adsorption experiments validated the technical potential of LC-CSP for practical electroplating wastewater management.

Optimization of Sol-Gel Catalysts with Zirconium and Tungsten Additives for Enhanced CF4 Decomposition Performance.

This study investigated the development and optimization of sol-gel synthesized Ni/ZrO2-Al2O3 catalysts, aiming to enhance the decomposition efficiency of CF4, a potent greenhouse gas. The research focused on improving catalytic performance at temperatures below 700 °C by incorporating zirconium and tungsten as co-catalysts. Comprehensive characterization techniques including XRD, BET, FTIR, and XPS were employed to elucidate the structural and chemical properties contributing to the catalyst's activity and durability. Various synthesis ratios, heat treatment temperatures, and co-catalyst addition positions were explored to identify the optimal conditions for CF4 decomposition. The catalyst composition with 7.5 wt% ZrO2 and 3 wt% WO3 on Al2O3 (3W-S3) achieved over 99% CF4 decomposition efficiency at 550 °C. The study revealed that the appropriate incorporation of ZrO2 enhanced the specific surface area and prevented sintering, while the addition of tungsten further improved the distribution of active sites. These findings offer valuable insights into the design of more efficient catalysts for environmental applications, particularly in mitigating emissions from semiconductor manufacturing processes.

Synergistic effect as a function of preparation method in CeO2-ZrO2-SnO2 catalysts for CO oxidation and soot combustion

The development of catalysts based on environmentally desirable components is a topical challenge. In the present work, we consider the effects of the preparation method on phase composition, porous structure, nature and distribution of active sites as well as synergistic behavior of components in two series of CeO2-ZrO2-SnO2 catalysts for soot combustion and CO oxidation. The catalysts prepared by the citrate method feature rather large SnO2 aggregates distributed on CeO2 and/or ZrO2 oxides. On the contrary, the catalysts prepared by the CTAB-templated approach feature a uniform distribution of oxide species and usually show higher activity in both CO oxidation and soot combustion. In both series, the activity and characteristics of catalysts are enhanced due to the synergistic effects arising when two or more oxide components coexist in their composition, and the degree of synergy is a function of the preparation method. The features of the most active catalysts combine (1) high specific surface area and pore volume, (2) high microstrain values, (3) coexisting oxygen vacancies of different nature, (4) high H2 consumption at low temperatures, and (5) high fraction of adsorbed active oxygen species.

Favorable formation of needle-shaped NiAl2O4 phase over macroporous Ni/CexZr1-xO2–Al2O3 catalysts in one-pot preparation and coke-resistant catalytic performance in dry reforming of methane

In this study, we report the formation of needle-shaped NiAl2O4 via favorable interactions between Ni and Al species over macroporous Ni/CexZr1-xO2–Al2O3 catalysts for dry reforming of methane (DRM) and its remarkable improvement in the catalytic performance. The macroporous catalysts prepared by a one-pot (OP) method promote a favorable interaction between Ni and Al species that results in the formation of unique needle-shaped NiAl2O4 due to easy access to each other compared with that by incipient wetness impregnation. The NiAl2O4 phase in the calcined catalysts transforms into highly dispersed Ni and defective Al2O3 via the Ni exsolution in the reduction step. The presence of oxygen vacancies near Ni0 species facilitates the CO2 activation and enhances the catalyst stability over DRM. The optimized distribution of active sites with abundant defects over macroporous Ni/CexZr1-xO2-Al2O3 catalysts (OP) result in high conversions of CH4 and CO2 and a low coking rate in DRM.