Catalytic Activity For Reduction Research Articles

Compact Disc-Derived Nanocarbon-Supported Catalysts with Extreme Catalytic Activity.

Advanced carbon-metal hybrid materials with controllable electronic and optical properties, as well as chemical reactivities, have attracted significant attention for emerging applications, including energy conversion and storage, catalysis and environmental protection. However, the commercialization of these materials is hampered by several vital problems, including energy-intensive synthesis and expensive chemicals, and inefficient control of their structures and properties. Herein, we report the simple and controllable engineering of nanocarbon-metal self-assembled silver nanocatalysts (SSNs) derived from polycarbonate (PC)-based optical discs using microplasmas under ambient conditions. The plasma-engineered catalysts exhibited controlled properties including surface functionalities, hydrophilicities, Ag+/Ag0 metallic states, and Ag loading. The synthesized catalysts leverage localized surface plasmon resonance (LSPR) properties, enabling enhanced catalytic activity for the rapid reduction of carcinogenic 4-nitrophenol (4-NP) to the valuable pharmaceutical intermediate 4-aminophenol (4-AP), achieving a high reaction rate constant of 0.2 ± 0.0 s-1 and completing the reduction in just 30 s. Demonstrating robust performance, the SSNs maintained up to 90% conversion efficiency after ten recycling cycles, underscoring their stability and reusability. This work not only presents an effective approach to upcycling optical disc waste, but also highlights the potential of plasma-engineered nanocatalysts in environmental remediation, offering a low-energy solution for high-efficiency pollutant reduction.

V‐/O‐Doping to Endow Ag2S‐based Bimetal Oxysulfide with Sulfur Vacancies and Heterovalent States for Rapid Reduction of Organic and Cr(VI) Pollutants in the Dark

AbstractA novel AgVOS oxysulfide catalyst for rapid catalytic reduction of toxic organic substances and Cr(VI) under dark is synthesized by a facile method. With the V/O co‐doping, the doped Ag2S catalyst has the effectively regulated electron transfer performance, the hydrazine‐driven V5+‐to‐V4+ reduction to disturb charge equilibrium, and the formed sulfur vacancy balanced by oxygen doping to maintain charge equilibrium. The formed sulfur vacancy acts as the active site for electrophilic nucleophilic reaction, while the orbital hybridization of O2p and S3p stabilizes the valence state of S2−. A suitable ratio of n(V4+/V5+) is regulated during the hydrazine‐driven synthesis to facilitate the electron transfer and enhance the V5+‐to‐V4+ reduction reaction. V/O co‐doped AgVOS‐3 prepared by a suitable hydrazine content exhibits super catalytic reduction performance of organic 4‐NP (4‐nitrophenol), MB (methyl blue), MO (methyl orange), and RhB (Rhodamine B, 20 ppm, 100 mL) dyes, which are completely reduced within 8, 8, 10, and 8 min, respectively. In comparison, Cr6+ (50 ppm, 100 mL) is also completely reduced within 6 min by AgVOS‐3, indicating its good catalytic reduction activity for organic and inorganic mixture pollutants. Furthermore, AgVOS‐3 has good stability after cyclic tests to maintain a reduction efficiency of 96.5%. Therefore, the AgVOS catalyst shows a promising application for industrial wastewater treatment.

Paper strips loaded with Ultrathin Gold Nanowires: Catalytic Activity and Stability in the p-nitrophenol reduction.

Oleylamine-coated ultrathin gold nanowires (AuNWs) were utilized to create catalytic platforms by simply dropping the colloidal synthesis product onto filter paper strips without additional treatment. These platforms were tested for...

Antioxidant and catalytic reduction activity of green synthesized gold nanoparticles using water-soluble chitosan

Antioxidant and catalytic reduction activity of green synthesized gold nanoparticles using water-soluble chitosan

Cu3P/CoP Heterostructure for Efficient Electrosynthesis of Ammonia from Nitrate Reduction Reaction.

Electrocatalytic nitrate reduction (ENO3RR) for ammonia production is one of the potential alternatives to Haber-Bosch technology for the realization of artificial ammonia synthesis. However, efficient ammonia production remains challenging due to the complex electron transfer process in ENO3RR. In this study, we fabricated a Cu3P/CoP heterostructure on carbon cloth (CC) by electrodeposition and vapor deposition, which exhibits an exceptional ENO3RR performance in alkaline medium, and showcases a Faradaic efficiency of ammonia (FENH3) and an ammonia yield rate as high as 97.95% and 17,637.3 μg h-1 cm-2 at -0.9 V vs RHE. Moreover, Cu3P/CoP also has excellent catalytic activity for nitrite reduction to ammonia, with an FENH3 up to 98.31% at -0.7 V vs RHE. The experimental and theoretical calculations reveal and confirm that the formation of a heterogeneous interface between Cu3P and CoP effectively promotes the electron transfer, where Cu3P as an electron donor induces the decrease of electron density around Cu and results in an enhancement of NO2- adsorption, thereby accelerating the ENO3RR process while inhibiting the competitive hydrogen evolution reaction (HER). Moreover, the metal phosphide catalyst facilitates the water dissociation, which accelerates the abundant *H generation, thus enhancing the subsequent hydrogenation process toward ENO3RR.

MOF-Derived MoC/WC Heterostructure as Bidirectional Catalyst for Lithium Polysulfide Enables High-Performance Lithium-Sulfur Batteries.

Since lithium-sulfur (Li-S) batteries have high energy density and environmental friendliness, they have garnered a lot of attention as a new type of energy storage technology. However, the shuttle effect of lithium polysulfides (LiPSs) and low utilization of sulfur (S) in Li-S batteries reduce the cycle stability and energy efficiency and limit their practical application. Therefore, it is urgent to achieve simultaneous immobilization and conversion of LiPSs utilizing catalysts. Herein, a metal-organic framework (MOF)-derived MoC/WC@NC heterojunction is synthesized as a bidirectional catalyst for LiPSs in high-performance Li-S batteries. Experimental and theoretical calculations indicate that the catalyst is expected to improve the catalytic activity for reduction and oxidation reactions of LiPSs, thereby accelerating the kinetics of Li-S batteries. In conclusion, with the incorporation of the novel catalyst between the cathodes and separators in Li-S batteries, the assembled batteries demonstrate excellent rate performance, with an initial discharge capacity of 1752.1 mAh g-1 at 0.1 C, and a discharge-specific capacity of 783.2 mAh g-1 even at 2 C. More significantly, the coulombic efficiency stayed above 99% and the capacity of 589.1 mAh g-1 after 1000 cycles at 1 C with a decay rate of only 0.062% each cycle.

Promotion effect of nitrogen doping on the low-temperature NH3-SCR of NO over activated carbon: Characterization and mechanism analysis

Heteroatom nitrogen doping in carbon catalysts is recognized an effective strategy for tailoring the properties of carbon catalysts for various flue gas de-NOx applications. However, accurately discerning the active structures after nitrogen doping and elucidating the promotion effect on low-temperature selective catalytic reduction activity remains a formidable challenge under different nitrogen doping preparation conditions. In this study, a series of nitrogen-doped activated carbon catalysts was synthesized through the L16(45) orthogonal array design method, and the degree of influence of various preparation conditions on de-NOx catalytic activities was also assessed. The optimal preparation conditions determined by range analysis were employed to synthesize NOAC-17, achieving the NO conversion of 95% and N2 selectivity of 99% at 300 °C, respectively. Subsequently, various characterization results proved that nitrogen doping induced the formation of abundant basic groups. The imine, amide, amine, and N-6 groups altered the acid-base of the activated carbon surface and increased the adsorption of acidic NOx. The N-5 and N-Q groups enhanced electronic interaction in the carbon matrix and accelerated electron mobility in the catalytic reaction process. Moreover, the N-6 group played multiple roles beyond the aforementioned effect due to its special structure. It also enhanced the accumulation of oxygen vacancies, which were closely associated with further oxidation of adsorbed NO. The lone electron pair in the N-6 group within the activated carbon framework can alter the polarity of the catalyst, thereby exerting a positive influence on the adsorption and activation of NH3. The nitrogen-doped catalyst identified through range analysis of the orthogonal experiment primarily facilitated the NH3-SCR reaction via the E-R mechanism with supplementary contribution from L-H mechanism at low temperatures. The nitrogen doping conditions obtained for the activated carbon catalyst provide valuable insights for the strategic enhancement of its catalytic performance in low-temperature NH3-SCR reactions.

Built-in electric field microenvironment of nickel cobalt phosphine/carbon nitride heterojunction for the enhanced visible-light-driven photocatalytic CO2 reduction

The greenhouse effect and the shortage of fossil energy are among the major issues that need to be addressed by the international community today. And graphite phase carbon nitride (g-C3N4, CN) is widely applied in catalysis because of its advantages of simple preparation, suitable band structure, high chemical and thermal stability. While some drawbacks limits its widespread application. In this study, different ratios of nickel cobalt phosphine/carbon nitride heterojunction photocatalyst (NiCoP/CN) was prepared by loading different amount NiCoP on the surface of CN using in-situ growth technology. The characterization results of XRD, SEM, TEM and XPS indicated that the synthesized NiCoP/CN heterojunction photocatalyst presented a highly wrinkled structure, which was conducive to the contact between the heterojunction photocatalyst and CO2. The combination of NiCoP with CN generated a unique figure of merit and created a built-in electric field, which facilitates the accumulation of photogenerated electrons in the CN region, thus providing a rich source of reducing electrons for the photocatalytic process. The catalytic reduction activity was assessed by the efficiency of photocatalytic CO2 reduction to simultaneous production of CO and CH4. The results indicated that compared with the original CN, the NiCoP/CN heterojunction photocatalyst exhibited excellent photocatalytic reduction performance of CO2. Among the prepared photocatalysts, the NiCoP-3/CN heterojunction photocatalyst had the best photocatalytic performance with CO and CH4 yields of 874.00 µmol g-1 h-1 and 408.00 µmol g-1 h-1. In addition, NiCoP is a kind of superior electronic conductor, and electrons in CN can effectively move towards NiCoP, which greatly inhibits the photo-induced recombination of charges and improves reduction efficiency.

(Invited) Exploring Electrochemical Methods to Enhance Catalytic Activity and Selectivity in Photoelectrochemical CO2 Reduction

Various electrocatalysts have undergone extensive examination regarding their capacity to selectively produce desired products via the electrochemical CO2 reduction reaction (CO2RR). Nonetheless, the efficiency of a CO2RR electrocatalyst does not guarantee the effectiveness of a co-catalyst on the semiconductor surface for photoelectrochemical CO2RR. Herein, we synthesize Bi2S3 nanorods and electrochemically reduce them to Bi nanoplates that adhere to substrates for use in electrochemical and photoelectrochemical CO2RR applications. Compared with bare Bi, the Bi2S3-derived Bi (S-Bi) nanoplates on carbon paper exhibit superior electrocatalytic activity and selectivity for formate (HCOO-) in the electrochemical CO2RR, achieving a Faradaic efficiency exceeding 93%, with minimal H2 production over a wide potential range. This highly selective S-Bi catalyst is being employed on the Si photocathode to investigate the behavior of electrocatalysts during photoelectrochemical CO2RR. The strong adhesion of the S-Bi nanoplates to the Si nanowire substrate and their unique catalytic properties afford exceptional activity and selectivity for HCOO- under simulated solar irradiation. The selectivity observed in electrochemical CO2RR using the S-Bi catalyst correlates with that seen in the photoelectrochemical CO2RR system. Combined pulsed potential methods and theoretical analyses reveal stabilization of the OCHO* intermediate on the S-Bi catalyst under specific conditions, which is critical for developing efficient catalysts for CO2-to-HCOO- conversion. These results emphasize the potential of S-Bi as an effective catalyst for CO2 reduction reactions and provide valuable insights into optimizing the reaction mechanisms and enhancing the product selectivity, especially in conjunction with co-catalysts for Si photocathodes.

High-entropy perovskite (Pr1/6Nd1/6Sm1/6Ba1/6Sr1/6)6/7(Mn1/6Co)6/7O3-δ as a highly active and CO2 durable cathode for solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are environmentally friendly energy conversion devices that convert the chemical energy in fuels directly into electrical power. The development of high-catalytic activity and durability cathode materials is crucial for the commercialization of SOFCs. Herein, a novel A-site deficient high-entropy perovskite oxide (Pr1/6Nd1/6Sm1/6Ba1/6Sr1/6)6/7(Mn1/6Co)6/7O3-δ (PNSBSMC) was designed. The strong disorder effect associated with entropy increase in high-entropy perovskite oxide is anticipated to accelerate oxygen reduction reaction (ORR) kinetics. PNSBSMC demonstrates excellent catalytic activity for oxygen reduction, primarily due to the entropy-driven enhancement that promotes oxygen adsorption, dissociation, and charge transfer dynamics. The increase in entropy not only significantly mitigates the thermal expansion of PNSBSMC but also provides additional pathways for ionic/electronic transport. At 800 °C, the PNSBSMC-based single cell achieved a remarkable peak power density of 1.41 W cm−2, representing an 88.0 % improvement over the single-phase PBC. Additionally, PNSBSMC demonstrates superior performance stability and CO2 tolerance. These findings suggest that high-entropy PNSBSMC perovskite holds significant potential as an effective cathode for SOFCs. This study offers new insights for the future development of high-stability, high-activity SOFC cathode materials.

Co–doped nitrogenated carbon nanotubes encapsulating CoNi alloys as bifunctional catalysts for urea-assisted rechargeable Zn-air battery

As a desirable alternative for oxygen evolution reaction (OER), urea oxidation reaction (UOR) with the effectively reduced overpotential has attracted considerable attention in pollutant degradation and rechargeable Zn-air battery (ZAB). Herein, a bifunctional electrocatalyst with CoNi alloy and Co–N dual active sites encapsulated by nitrogen-doped carbon nanotubes have been rationally designed and successfully prepared. The as-obtained catalyst CoNi/Co–NCNT displays excellent catalytic activity for oxygen reduction (ORR) and UOR with a narrow potential difference of 0.56 V. The urea-assisted rechargeable ZABs based on CoNi/Co–NCNT provide higher energy conversion efficiency (61%), 15% higher than that of conventional ZABs. In addition to verify the UOR pathway on the CoNi/Co–NCNT, DFT calculations reveal that CoNi alloy and Co–N in CoNi/Co–NCNT synergistically function as the main active sites for ORR and UOR. The excellent ORR catalytic performance and the superior energy conversion efficiency of CoNi/Co–NCNT based urea-assisted rechargeable ZAB is expected to accelerate the practical application of ZAB technology. This work paved a new way for the development of bifunctional catalysts for higher efficiency ZABs, and also provides a potential scheme for disposing urea rich wastewater.

Catalytic reduction, antibacterial, and antioxidant activities of green synthesized silver nanoparticles using Coccinea grandies (L) Voigt leaf extract

In this study, silver nanoparticles (AgNPs) were synthesized using the aqueous extract of Coccinia grandis (L) Voigt leaf (CGL) extract using microwave irradiation method and the structure was elucidated by various techniques such as UV–Visible spectroscopy, Fourier transformation infrared spectroscopy (FT-IR), x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HR-TEM). The UV–visible spectroscopy confirmed the formation of AgNPs and SPR band appear at 420 nm. FT-IR analysis indicated the presence of –OH and –NH functional groups from secondary molecules of CGL capping the AgNPs surface. HR-TEM revealed spherical aggregates with an average size of 29.4 nm. EDX confirmed the presence of elemental silver. XRD analysis showed that the AgNPs had a face-cantered cubic (FCC) crystal structure. The CGL-AgNPs were used as a heterogeneous catalyst to reduce RhB and CR dyes from aqueous solutions in the presence of sodium borohydride (NaBH4). The results showed that greater than 95 % of catalytic reduction can be accomplished within 9 min. The biosynthesized AgNPs demonstrated notable antioxidant activity (82.89 % in the DPPH assay) and antibacterial activity with a Zone of inhibition ranging from 9 to 11 mm. These findings suggest that CGL can be used to synthesize new, cost-effective AgNPs using an environmentally friendly approach.

Revealing insights into the unexpected effects of ZnO on selective catalytic reduction (SCR) activity of the CeOx-WO3 catalyst

This study delved into the intriguing impact of zinc oxide (ZnO) on the selective catalytic reduction (SCR) performance of a CeOx-WO3 catalyst with a Ce/W molar ratio of 3:2 (denoted as CW). The introduction of ZnO, at low concentrations of 1 wt% or 3 wt%, resulted in a diminution of the catalyst’s surface acid sites, which hampered the adsorption of NH3 and negated the benefits of improved NH3 activation due to the enhanced oxidative capacity. Consequently, the proceeding of the SCR reactions was significantly impeded, with a marked decrease in NOx conversion to approximately 42 % at 200 °C, which was nearly half that of the virgin CW catalyst. In contrast, increasing ZnO loading to 5 wt% facilitated the formation of ZnWO4, which introduced additional strong acid sites and bolstered NH3 adsorption at moderate and high temperatures. This, in conjunction with the heightened reactivity of surface Ce4+, resulted in a resurgence of deNOx performance, with a NOx conversion increase of ∼ 13 % at 250 °C compared to the catalyst with 3 wt% ZnO. Conversely, escalating ZnO loading to 7 wt% disrupted the formation of ZnWO4 and the excess ZnO neutralized the catalyst’s acid sites, thereby hindering NH3 adsorption and reducing NOx conversion. These insights were instrumental for the prospective application of the CeOx-WO3 catalysts under heavy metal-rich conditions.

Atomic-scale mechanistic study of oxygen reduction mechanism for B-site doped Pr(Ba,Sr)Co2O5+δ by density functional theory calculations

Pr(Ba,Sr)Co2O5+δ is a promising cathode material for solid oxide fuel cell (SOFC) due to its high oxygen ion transport capability and oxygen reduction activity. Density functional theory (DFT) calculations were performed to elucidate the oxygen reduction mechanism of B-site doped Pr(Ba,Sr)(Co,M)2O5+δ (M = Fe, Ni, Cu, and Zn) materials. First, we investigated the formation of O vacancies. The results indicate that Cu and Zn doping facilitate O vacancy formation, resulting in lower O vacancy formation energies. Furthermore, the interaction between oxygen and the (0 0 1) surfaces of B-site doped Pr(Ba,Sr)(Co,M)2O5+δ has been comprehensively discussed, involving both perfect and defective surfaces. The results demonstrate that the presence of O vacancies enhances the catalytic activity for oxygen reduction, by reducing the energy required for O2 dissociation. Zn-doped Pr(Ba,Sr)(Co,M)2O5+δ exhibits a low O vacancy formation energy, resulting in a stable adsorption configuration upon oxygen dissociation, indicating its potential as a cathode material for SOFC.

In-situ imaging and time-resolved investigation of local pH in electrocatalytic CO2 reduction

Local pH near the catalyst surface exerts a substantial influence on both catalytic selectivity and activity in electrocatalytic CO2 reduction (CO2RR). While the investigation of local pH remains challenging in the aspect of in-situ imaging and monitoring. In this study, a novel lateral-type surface-enhanced Raman spectroscopy (L-SERS) system with a wide pH testing range from acidic to alkaline, is developed for the in-situ observation of local pH distributions with high spatial and temporal resolution during CO2RR. Excellent in-situ imaging of local pH near the catalyst surface is obtained, showing good consistency with simulation results. Besides, the gradual pH elevation and stabilization can be monitored via this time-resolved local pH investigation. This study presents a direct visualization of local pH distribution and variation at the Nernst layer during CO2RR, providing direct evidence in local pH for the feasibility of acidic electrolyte and offering theoretical guidance for optimizing CO2RR conditions.

Basic understanding of Cu‐SSZ‐13 in catalyzing low‐temperature selective catalytic reduction of NOx by ammonia

AbstractThe development of Cu‐SSZ‐13 represents a significant breakthrough in the field of NOx removal from mobile exhaust, demonstrating excellent selective catalytic reduction (SCR) activity across a broad temperature range (200–500°C). However, the limited reactivity of Cu‐SSZ‐13 at temperatures below 200°C poses a challenge for the removal of NOx emitted during vehicle cold starts. To stimulate new efforts to enhance low‐temperature SCR performance, this review provides a fundamental understanding of the nature of Cu‐SSZ‐13 in catalyzing the SCR reaction. The structures, coordination environments, and oxidation states of Cu2+ during the SCR reaction, as well as the redox cycle pathway of Cu2+ ions and the characteristics of the rate‐determining step, were discussed. Based on these insights, several strategies for improving the low‐temperature activity of Cu‐SSZ‐13 are proposed. Finally, the review offers a perspective on the future of low‐temperature SCR of NOx over Cu‐SSZ‐13.

GREEN SYNTHESIS OF CaO–PdNps FROM LAWSONIA INERMIS LEAF EXTRACT: CATALYTIC REDUCTION OF METHYLENE BLUE WITH CENTRAL COMPOSITE DESIGN-ENHANCED NEURAL NETWORK PREDICTION

In this work, small-sized CaO–PdNps nanocomposites were synthesized using Lawsonia inermis leaf extract as a reducing and capping agent. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to analyze the produced nanocomposites. Based on these investigations, the average particle size was found to be [Formula: see text][Formula: see text]nm, with a predominantly spherical morphology. The resulting nanocomposite was then tested for catalytic activity in methylene blue reduction. The mass of the catalyst and dye, the concentration of sodium borohydride ([NaBH4]), and the reaction time were all optimized using a central composite design (CCD). A significant correlation between predicted and experimental degradation percentages was shown by the CCD model ([Formula: see text]), which also proved statistically significant (p-[Formula: see text]). Furthermore, a deep learning neural network (DLNN) was used to improve the prediction accuracy over and beyond CCD. There was a good connection between the two models as a result of using the CCD output as DLNN validation data. Mean absolute error (MAE), mean squared error (MSE), root mean squared error (RMSE), mean absolute percentage error (MAPE), and [Formula: see text] were used to assess the performance of the DLNN. The results ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]) validated that all four metrics were successful in forecasting the percentage of degradation.

Green synthesis of copper oxide nanoparticles using solanum melongena seeds extract and its applications in degradation of Rose Bengal dye, antibacterial, catalytic reduction and antioxidant activity

The generation of copper oxide (CuO) nanoparticles using a biogenic extract (solanum melongena seeds) was the primary focus of this study. As prepared catalyst has been utilized for dye degradation of Rose Bengal and studies on Antibacterial and Antioxidants. The catalyst was characterized for its structural aspects by using Scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS), Powder X-ray Diffraction (PXRD), Fourier Transform - InfraRed spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), Brunauer-Emmett-Teller (BET) and UV–Visible DRS. The characterization results of XRD shows that the catalyst is in monoclinic phase. Copper Oxide is irregular in morphology and the average particle size is 47.97 nm which can be obtained using the SEM images and EDS spectra shows the Oxygen and Copper atoms presence which indicates the free from impurities of the fabricated biogenic CuO nanoparticles. FT-IR result indicated the stretching frequency of Cu–O appears at 487 cm−1. TGA data reveal that high-purity and thermally stable nanoparticles were fabricated, by the absence of significant weight losses at temperatures greater than 400 °C. Through UV–Visible DRS the calculate band gap was found to be 2.8eV. Based on the characterisation results the best catalyst was used to degrade the Rose Bengal dye within 60 min and also carried out the antibacterial and antioxidant activity which was found to be satisfactory when compared with their standard values.

Adsorption Performance and Photocatalytic Activity of La-TiO2@kaolin Composites

Abstract La-TiO2@kaolin(LTK) composites were prepared via sol-gel method with kaolin, lanthanum nitrate and tetrabutyl titanate as raw materials. The samples were characterized by XRD, SEM/EDS, and UV-Vis. The visible light photocatalytic reduction activity and adsorption performance of samples for Cr(VI) were studied. The results showed that La doping can refine TiO2 grains, stabilize phase structure of anatase TiO2, and expand its absorption spectrum, thereby enhancing its photocatalytic reduction activity. Due to the composite of kaolin, the dispersion of TiO2 is improves and it is endowed with a large specific surface area lead to enhance its adsorption ability for Cr(VI). The adsorption equilibrium process of LTK for Cr(VI) conforms to the Langmuir equation model. The coupling effect of doping and composite modification improves the adsorption and visible light catalytic reduction activity of Cr(VI) over composite material samples. The adsorption-photocatalytic removal rate of LTK for Cr(VI) under visible light irradiation for 6 hours reached the highest of 96.5%. The apparent first-order kinetic constant of its photocatalytic reduction reaction was 2.6 times that of pure TiO2.

Unraveling the NH3-SCR-DeNOx Mechanism of Cu-SSZ-13 Variants by Spectroscopic and Transient Techniques.

Commercial SSZ-13 zeolite with different n(Si)/n(Al) ratios and from different suppliers were subjected to a post-synthetic treatment in order to create mesopores of up to 15 nm. Furthermore, the materials were modified with copper ions and thoroughly physico-chemically characterized. The modified textural properties varied the nature of copper species, and thus, activity in the selective catalytic reduction of NOx with ammonia (NH3-SCR-DeNOx). Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) studies with hexane as probe liquid revealed improved intracrystalline diffusion for some Cu-containing SSZ-13 materials. The NH3-SCR-DeNOx pathways are verified via in situ DR UV-Vis, in situ FT-IR and EPR, temperature-programmed studies as well as SSITKA studies that provide a mechanistic understanding of the reaction. Kinetic modelling results demonstrate the highest NH3-SCR-DeNOx reaction rates and up to 20 % lower energy barriers with n(Si)/n(Al) ratio of 6.5 for all modified forms (i. e., (NH4)Cu-SSZ-13_6.5 and Cu-SSZ-13_6.5_NaOH/0.1) and cause only negligible parasitic ammonia oxidation. The modelling of the stop-flow experiments further demonstrates that the SCR pathway via the HONO surface intermediate is present but barely contributes to the overall NO conversion compared to the dominant path between adsorbed NH3 and NO from the gas phase.