UV Vis Diffuse Reflectance Spectroscopy Research Articles

Mapping the Methanol-to-Gasoline Process Over Zeolite Beta.

Decarbonizing the transportation sector is among the biggest challenges in the fight against climate change. CO2 -neutral fuels, such as those obtained from renewable methanol, have the potential to account for a large share of the solution, since these could be directly compatible with existing power trains. Although discovered in 1977, the zeolite-catalyzed methanol-to-gasoline (MTG) process has hardly reached industrial maturity, among other reasons, because maximizing the production of gasoline range hydrocarbons from methanol has proved complicated. In this work, we apply multimodal operando UV/Vis diffuse reflectance spectroscopy coupled with an online mass spectrometer and "mobility-dependent" solid-state NMR spectroscopy to better understand the reaction mechanism over zeolites H-Beta and Zn-Beta. Significantly, the influential co-catalytic role of oxymethylene species is linked to gasoline formation, which impacts the MTG process more than carbonylated species.

Enhanced photocatalytic activity of cubic ZnSn(OH)6 by in-situ partial phase transformation via rapid thermal annealing

In this study, a mixed phase ZnSn(OH)6/ZnSnO3 photocatalyst was synthesized by calcining ZHS nanostructures via rapid thermal annealing (RTA) process. The composition ratio of ZnSn(OH)6/ZnSnO3 was controlled by changing the duration of the RTA process. The obtained mixed-phase photocatalyst was characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, ultraviolet photoelectron spectroscopy, photoluminescence, and physisorption analysis. Results showed that ZnSn(OH)6/ZnSnO3 photocatalyst obtained by calcining ZHS at 300 °C for 20 sec displayed the best photocatalytic performance under UVC light illumination. Under optimized reaction conditions, ZHS-20 (0.125 g) demonstrated nearly complete removal (>99%) of MO dye in 150 min. Scavenger study revealed the predominant role of OH• in photocatalysis. The enhanced photocatalytic activity of the ZnSn(OH)6/ZnSnO3 composites was mainly ascribed to the photosensitization of ZHS by ZTO and effective electron-hole separation at the ZnSn(OH)6/ZnSnO3 heterojunction interface. It is expected that this study will provide new research input for the development of photocatalyst through thermal annealing-induced partial phase transformation.

Studies on High-Temperature Evolution of Low-Loaded Pd Three-Way Catalysts Prepared by Laser Electrodispersion.

Pd/Al2O3 catalyst of the "crust" type with Pd loading of 0.03 wt.% was prepared by the deposition of 2 nm Pd particles on the outer surface of the alumina support using laser electrodispersion (LED). This technique differs from a standard laser ablation into a liquid in that the formation of monodisperse nanoparticles occurs in the laser torch plasma in a vacuum. As is found, the LED-prepared catalyst surpasses Pd-containing three-way catalysts, obtained by conventional chemical synthesis, in activity and stability in CO oxidation under prompt thermal aging conditions. Thus, the LED-prepared Pd/Al2O3 catalyst showed the best thermal stability up to 1000 °C. The present research is focused on the study of the high-temperature evolution of the Pd/Al2O3 catalyst in two reaction mixtures by a set of physicochemical methods (transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance UV-vis spectroscopy). In order to follow the dispersion of the Pd nanoparticles during the thermal aging procedure, the testing reaction of ethane hydrogenolysis was also applied. The possible reasons for the high stability of LED-prepared catalysts are suggested.

Preparation of Two-Dimensional Layered CeO2/Bi2O3 Composites for Efficient Photocatalytic Desulfurization

A two-dimensional layered CeO2/Bi2O3 composite was synthesized by microwave solvothermal method. X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), UV-Vis diffuse reflection spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) were used to studied crystal structure, morphology, optical performance, elemental composition and the surface electronic state of the samples. The photocatalytic properties of the prepared samples were evaluated by photocatalytic desulfurization under visible light. When the molar ratio of Ce and Bi was 1:2, CeO2/Bi2O3 composite presented the highest photocatalytic desulfurization rate. Transient Photocurrent measurement, electrochemical impedance spectroscopy (EIS) and photoluminescence spectroscopy (PL) showed that CeO2 and Bi2O3 formed a heterojunction, which could promote the separation of photogenerated electrons and holes, improving the photocatalytic activity. Furthermore, it was found that the active species of hydroxyl radical (·OH) played an important role in the photocatalytic degradation of dibenzothiophene (DBT) based on the active species capture experiment. Finally, a plausible mechanism for the photocatalytic oxidative desulfurization of this nanocomposite was proposed.

Photodegradation of Oxytetracycline Using Fluorescent Light Driven ZnO Quantum Dots Synthesised Via Microwave Method

In this study, Li+ ions capped zinc oxide quantum dots (ZnO QDs) was synthesised using the microwave method. The X-ray diffraction (XRD), transmission electron microscopy (TEM), high-transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), UV–Visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) techniques were used to characterise the structural, morphological, optical properties of the ZnO QDs. The XRD analysis reveals that ZnO QDs have a hexagonal wurtzite structure with an average crystallite size of 9.9 nm. The morphology of ZnO QDs was observed to be quasi-spherically shaped with an average particle size of 10 nm. The PL analysis detected the presence of various defects. All these factors enhanced the photodegradation of oxytetracycline (OTC) under fluorescent light irradiation. Within 40 min, 88.3% of OTC was removed, which was higher compared to the bulk ZnO reported in the literature. This technology is aimed at small animal husbandries due to the photocatalyst synthesis method’s simplicity and the photocatalysis process’s requirements.

Facile synthesis of anatase TiO2 nanoparticles using titanium metal and its enhanced photocatalytic activity under visible light

A green sol-gel method was employed to synthesize TiO2 nanoparticles (NPs) using titanium metal. The syn-thesized TiO2 NPs underwent comprehensive characterization using techniques including X-ray diffraction (XRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), and UV–Vis diffuse reflectance spectroscopy (UV-Vis DRS) to evaluate their structure, morphology, and spectral properties. By adjusting the amount of oxalic acid, tailored physico-chemical properties of anatase TiO2 catalysts were achieved. The obtained TiO2 catalysts demonstrated a high surface area, excellent absorption, and remarkable photocatalytic degradation of methylene blue under visible light irradiation. This enhancement is primarily contributed by the large surface area and oxygen vacancies.

Enhancement of ZnO@RuO2 bifunctional photo-electro catalytic activity toward water splitting.

Catalytic materials are the greatest challenge for the commercial application of water electrolysis (WEs) and fuel cells (FCs) as clean energy technologies. There is a need to find an alternative to expensive and unavailable platinum group metal (PGM) catalysts. This study aimed to reduce the cost of PGM materials by replacing Ru with RuO2 and lowering the amount of RuO2 by adding abundant and multifunctional ZnO. A ZnO@RuO2 composite in a 10:1 molar ratio was synthesized by microwave processing of a precipitate as a green, low-cost, and fast method, and then annealed at 300°C and 600°C to improve the catalytic properties. The physicochemical properties of the ZnO@RuO2 composites were investigated by X-ray powder diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The electrochemical activity of the samples was investigated by linear sweep voltammetry in acidic and alkaline electrolytes. We observed good bifunctional catalytic activity of the ZnO@RuO2 composites toward HER and OER in both electrolytes. The improved bifunctional catalytic activity of the ZnO@RuO2 composite by annealing was discussed and attributed to the reduced number of bulk oxygen vacancies and the increased number of established heterojunctions.

Synthesis, characterization and investigation of hydrophobic and self-cleaning properties of modified Zn–Mn and Cu–Mn nano spinels

Nano spinels of zinc-manganite and copper-manganite were synthesized by the co-precipitation method. Characterization of synthesized nanoparticles has been carried out using X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV–vis diffuse reflectance spectroscopy (DRS), Field emission scanning electron microscopy (FESEM) and Atomic force microscopy (AFM) methods resulting in confirmation of the target phase formation performance of synthesized nanoparticles evaluated in photodegradation methyl red organic dye. In addition, synthesized nanoparticles were coated on sand-blasted glass and modified using palmitic acid to reach the hydrophobic surface. The contact angles of water droplets were measured for both surfaces which were 159° and 152° for zinc-manganite and copper manganite, respectively. The hydrophobicity of both coatings was available after 360 days making them a good candidate for the production of hydrophobic coating with photocatalytic activity in a blend with cement-like materials.

Sunlight-driven photocatalytic degradation of ciprofloxacin and organic dyes by biosynthesized rGO–ZrO2 nanocomposites

Aquatic ecology has been greatly threatened by the discharge of effluents of textile and antibiotic industries into natural waters. Herein, an efficient and easily recycled reduced graphene oxide/zirconium oxide nanocomposite has been synthesized using banana peel extract (abbreviated as rGO-ZrO2 in this work). The X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy were used to analyze the synthesized material. The as-prepared rGO-ZrO2 nanocomposite was employed as a photocatalyst for the decomposition of rhodamine blue (RhB) and crystal violet (CV) dyes, and ciprofloxacin (CIP) antibiotic by illumination with direct sunlight. The RhB and CV were degraded to maximum extent of around 86 and 90%, respectively, over the rGO-ZrO2 nanocomposite after exposure to direct sunlight for 120min. On the other hand, the degradation of CIP was approximately 93.1% over the rGO-ZrO2 nanocomposite in 240min under same experimental conditions. Further studies were performed regarding the role of parameters like pH, catalyst dose, and scavengers, in order to understand the superiority of rGO-ZrO2 nanocomposite in degrading organic pollutants. Moreover, the intermediate products and plausible CIP degradation mechanisms were examined using liquid chromatography-mass spectrometry (LC-MS). Moreover, the catalyst was easily separated from the solution and demonstrated good stability and reusability. The RhB, CV, and CIP removal efficiency were 80%, 83%, and 88%, respectively, after five cycles.

Growth of TiO2–CdO coated films: A brief study for optoelectronic applications

Current work reports the deposition of pure and TiO2 doped CdO printed films on glass substrate via cost-effective screen-printing method and then sintered at 550 °C for 10 min. The pure TiO2, CdO and TiO2–CdO coated films were used to investigate the structural, morphological and opto-electrical properties by different analytical techniques. X-ray diffraction pattern of polycrystalline doped analogue confirms the existence of TiO2 anatase phase and cubic phase of CdO with a maximum diffraction of (101) plane. Surface morphology is derived from scanning electron microscopy finding out porous images along with EDS results to confirm the desired composition. The spectra of UV–Vis diffused reflectance spectroscopy and photoluminescence absorbance peaks show a red shift due to change in reflectance. IR transmittance spectra recorded in 4000-400 cm−1 region exhibits the stretching modes of O–Ti–O and Cd–O groups present in these samples. The current vs. voltage (IV) characteristics and direct current conductivity measurement shows p-n junction diode behaviour. All the parameters were calculated and described in-depth, including structural, optical and electrical properties. The obtained results suggest that TiO2–CdO thick film could be used in optoelectronic applications due to the shift in optical radiation absorption to visible region, reduction in recombination rate of charge carriers and increase in electrical conductivity.

Heteropolyacid-loaded MOF-derived mesoporous zirconia catalyst for chemical degradation of rhodamine B

Abstract In this article, silicotungstic acid (STA)-loaded metal–organic framework (MOF)-derived composites (C-STA@ZrO2) were successfully synthesized by simple strategies. X-ray diffraction, Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray, N2 physisorption, UV-vis diffuse reflection spectroscopy, and X-ray photoelectron spectroscopy techniques were used to characterize the as-obtained composites. Intriguingly, C-STA@ZrO2 exhibits excellent photocatalytic performance, and rhodamine B (RhB) (40 mg·L−1) in water can be degraded to 93.9% after 120 min of irradiation. Moreover, various catalysts, catalyst dosage, and dye concentrations on RhB degradation were evaluated. Besides, the reusability of C-STA@ZrO2 was also investigated. This work may provide a new and significant guideline for exploring excellent performance of MOF-derived hybrid material for wastewater purification.

Structural modification of nano titania by doping with Barium and Copper – Impact on photocatalysis: Applications in degradation of dye and pathogens

Ba/Cu co-doped TiO2 nanoparticles with visible light activity were fabricated by the sol-gel method with different weight percentages for the decontamination of toxic organic azo dye pollutants. The characterizations of fabricated samples were evaluated by using UV–Vis Diffuse Reflectance Spectroscopy, X-ray Diffraction Spectroscopy, Brunauer-Emmett-Teller, Transmission Electron Microscopy, Scanning Electron Microscopy-Energy Dispersive X-ray, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, and X-ray Fluorescence techniques. The results of co-doping revealed a lower band gap of 2.59 ​eV (UV–Vis DRS), a high surface area of 138 ​m2/g (BET), and anatase phase formation (XRD), which are the major contributing factors for efficient photocatalytic activity. SEM-EDX and TEM analyses showed the rough morphology, uniform distribution of dopants with spherical shape. XPES and XRF confirmed the incorporation of Ba and Cu into TiO2 lattice. Owing to the results of Ba/Cu co-doped samples, BCT3 (Ba-0.25% and Cu-0.75%) has shown the best photocatalytic activity by degrading carcinogenic food/textile dye Amaranth, within 50 ​min with optimum reaction parameters of pH ​= ​3, catalyst dosage of 0.1 ​g/L, and dye concentration of 10 ​mg/L under visible light irradiation. BCT3 showed efficient antibacterial activity when tested for Bacillus subtilis (gram ​+ ​ve) and Klebsiella pneumoniae (gram -ve).

Silver oxide-zeolite for removal of an emerging contaminant by simultaneous adsorption-photocatalytic degradation under simulated sunlight irradiation

The existence of contaminants of emerging concern such as pharmaceuticals in the water sources become a growing concern matter because of their increased consumption, incomplete disposal, and potential impacts on living organisms. Accordingly, the removal of these bioactive compounds from the aqueous environment also becomes a vital issue and different treatment techniques have been investigated. The novelty of this work lies in the synthesis and implementation of silver oxide anchored on Y zeolite (Ag2O@Y Zeo) as an untried effective photocatalyst for the removal of emerging contaminants. Ranitidine (RANI) removal from aqueous solutions was investigated in this study by simultaneous adsorption-photodegradation induced via simulated sunlight irradiation in the presence of Ag2O@Y Zeo. Ag2O@Y Zeo was prepared by thermal treatment at 400 °C of Ag-form Y zeolite which was prepared by ion-exchange. The produced catalyst was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive analysis by X-ray, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, UV–Vis diffuse reflection spectroscopy and photoluminescence spectroscopy. The simultaneous adsorption-photodegradation of RANI using Ag2O@Y Zeo was investigated at various conditions including a catalyst dose (5, 10, 30, 50, and 70 mg/ 100 mL), an initial RANI concentration (10, 20, 30, 40, and 50 mg/L), and a solution pH (3, 5, 9, and 11). According to the results, the RANI removal percentage was 97.51% obtained at Ag2O@Y Zeo dosage of 30 mg/100 mL, an initial RANI concentration of 40 mg/L, a solution pH of 7.4 and a time of 75 min. These results were attributed to the important role of the photogenerated holes and photogenerated electrons over the synthesized catalyst and their generation can be induced only in the presence of simulated sunlight. The photodegradation process of RANI by Ag2O@Y Zeo followed the pseudo-first-order kinetic model and O2°- was the main reactive species.

A porphyrin derivative with highly red shifted and intensified absorption bands immobilized into the mesopores of nanostructured amberlite: Synthesis, characterization and photocatalytic activity

The BF3 complex of meso-tetra(4-sulfonatophenyl)porphyrin (H2TPPS4), immobilized into the pores of a new nano-structured mesoporous anion exchange polymer, nanoAmbN(Me)3Cl (Amb = Amberlite IRA-410(Cl)) was used as the photosensitizer for aerobic oxidation of organic compounds. NanoAmbN(Me)3Cl, nanoAmbN(Me)3@H2TPPS4 and nanoAmbN(Me)3@H2TPPS4(BF3)2, were characterized by IR and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) methods, TGA, FESEM, elemental mapping (SEM-EDX) and BET. The nanocomposite was used as photosensitizer in the aerobic oxidation of 1,5-dihydroxynaphthalene (DHN) and cyclohexene in acetonitrile. The results were compared with those obtained in the presence of the BF3 complex of meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (H2TMPyP) immobilized on nanostructured amberlyst 15. The observed red shifts in the UV–vis DRS UV–vis spectrum upon the formation of nanoAmbN(Me)3@H2TPPS4(BF3)2 were much larger than those of nanoAmbSO3@H2TMPyP(BF3)2. The singlet quatum yield of nanoAmbN(Me)3@H2TPPS4 and nanoAmbN(Me)3@H2TPPS4(BF3)2 was determined by using 1,3-diphenylisobenzofuran (DPBF) and DHN as the quenchers of singlet oxygen, for the excitation of the photosensitizers in the Q and Soret band regions, respectively.

Characterisation and application of bismuth ferrite - bismuth vanadate p-n heterojunction in the photoelectrocatalytic degradation of ciprofloxacin in water

Towards the photoelectrocatalytic degradation of ciprofloxacin, BFO/BVO heterojunction was constructed to improve the performance of the individual semiconductors. The enhanced performance of the heterojunction photoanode was attributed to increase in visible light harvesting, greater current mobility leading to higher current density, low charge transfer resistance, and low recombination rate of photogenerated electron and hole. The BFO, BVO and BFO/BVO photoanodes prepared were immobilized on fluorine doped tin oxide coated glass and characterised using x-ray diffractometry, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy (EIS), UV–vis diffusive reflectance spectroscopy, photocurrent measurement, ultra performance liquid chromatography- mass spectrometry (UPLC-MS). The percentage removal of ciprofloxacin using BFO, BVO and BFO/BVO photoanodes were 56%, 49% and 80.3% respectively. The current density of the heterojunction photoanode were markedly improved when compared to the individual performances of the photoanodes. Also, the BFO/BVO heterojunction photoanode showed stability after repeated usages. Data from UPLC-MS studies was used to propose the degradation pathway, products, and mechanism of the degradation process. .

Palladium-modified TiO2 Photocatalysts: Synthesis, Characterization, and Environmental Application

Sol-gel method was used to prepare palladium-modified TiO2 powder photocatalysts (Pd atomic percentage range of 0–1.00). The materials were characterized by X-ray diffraction, N2 physisorption, UV–Vis diffuse reflectance spectroscopy and transmission electron microscopy. Photocatalytic activity was tested for phenol degradation, with UV and visible lamps. The optimum palladium content was determined (0.10% atomic Pd), showing phenol degradation of 100% under UV irradiation (2 h) and 68% under visible irradiation (5 h). The presence of PdO particles was revealed on this material. Furthermore, the immobilization of this material on glass slides was studied by dip-coating method to overcome the limitations of the slurry mode. This film presented photocatalytic activity under UV and visible irradiation (5 h), reaching 80% and 23% of phenol degradation, respectively. This film is a promising alternative to degradation of pollutant using solar irradiation effectively.

Enhancement of the photocatalytic performance of Y2O3–ZnO nanocomposites under visible light: Towards multifunctional materials for electronic and environmental applications

ZnO doping with different yttrium rare earth element concentrations was synthesized using a simple, effective, and inexpensive combustion technique. The structural morphologies of the proposed Y2O3-doped nanostructures were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transformation Infrared spectroscopy (FT-IR) techniques. The obtained results encouraged the ZnO growth to a satisfactory nanoparticle structure. As varying the yttrium ratios, the crystallinity of the host ZnO material was modified, which supports the growth efficiency and the doping effects. The linear optical, energy bandgap, dielectric and electrical parameters for the studied Y2O3–ZnO nanomaterials were characterized using UV–Vis diffuse reflectance spectroscopy, current-voltage, and AC electrical conductivity characteristics. The efficiency of photocatalytic degradation for different dyes, including Methylene Blue, Phenol, and Rhodamine B, was considered applying all Y2O3–ZnO nanostructures. Increasing the yttrium in the ZnO matrix improved the photocatalytic efficiency. For Y2O3–ZnO (S5), the optimal photocatalyst was a 100% degradation for Phenol, Methylene Blue, and Rhodamine B solutions compared to 80% photocatalysis using pure ZnO. The proposed Y2O3-doped ZnO nanocomposites are promising applicants for numerous biomedical, optical, environmental, varistors, and photocatalytic nanodevices.

Hydrothermal synthesis of Ce2Sn2O7 nanoparticles for effective sonocatalytic performance

The Ce2Sn2O7 nanoparticles were successfully synthesized using a simple hydrothermal method. The crystal structure, morphology, and optical property of Ce2Sn2O7 nanoparticles were analyzed by X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy and UV–visible diffuse reflectance spectroscopy. The nanomaterial was first applied to ultrasonic catalytic degradation. The sonocatalytic activity of Ce2Sn2O7 nanoparticles was evaluated at room temperature and in the dark by using the Methyl Orange (MO) as the simulated contaminant. The effects of ultrasonic output power, Ce2Sn2O7 addition amount, initial concentration of pollutants, pH of solution, types of organic dyes and other factors on the catalytic degradation efficiency were investigated. The experiment results show that the ultrasonic catalytic degradation reaction of MO by the Ce2Sn2O7 nanoparticles basically follows the pseudo first-order kinetic model. Under the best conditions, the ultrasonic catalytic degradation rate of Methyl Orange reaches 97.8%, and the degradation rate can still reach 82.6% after four cycles of experiments. These results indicate that Ce2Sn2O7 nanoparticles can be used as acoustic catalyst for the purification of organic wastewater, which has a good application prospect.

Controllable Doping of Mn into Ni0.075-xMnxAl0.025(OH)2(CO3)0.0125·yH2O for Efficient Adsorption of Fluoride Ions.

Here, the structural, optical, and adsorptive behaviors of Ni0.075-xMnxAl0.025(OH)2(CO3)0.0125·yH2O (Ni-Mn/Al) layered double hydroxides (LDHs) are investigated to capture fluoride from aqueous media. The 2D mesoporous plate-like Ni-Mn/Al LDHs are successfully prepared via a co-precipitation method. The molar ratio of divalent to trivalent cations is maintained at 3:1 and the pH at 10. The X-ray diffraction (XRD) results confirm that the samples consist of pure LDH phases with a basal spacing of 7.66 to 7.72Å, corresponding to the (003) planes at 2θ of 11.47o and the average crystallite sizes of 4.13 to 8.67nm. The plate-like Mn-doped Ni-Al LDH consists of many superimposed nanosheets with a size of 9.99nm. Energy-dispersive X-ray and X-ray photoelectron spectroscopies confirm the incorporation of Mn2+ into the Ni-Al LDH. UV-vis diffuse reflectance spectroscopy results indicate that incorporating Mn2+ into LDH enhances its interaction with light. The experimental data from the batch fluoride adsorption studies are subjected to kinetic models such as pseudo-first order and pseudo-second order. The kinetics of fluoride retention on Ni-Mn/Al LDH obey the pseudo-second-order model. The Temkin equation well describes the equilibrium adsorption of fluoride. The results from the thermodynamic studies also indicate that fluoride adsorption is exothermic and spontaneous.

Defects Tune the Strong Metal-Support Interactions in Copper Supported on Defected Titanium Dioxide Catalysts for CO2 Reduction.

A highly active and stable Cu-based catalyst for CO2 to CO conversion was demonstrated by creating a strong metal-support interaction (SMSI) between Cu active sites and the TiO2-coated dendritic fibrous nano-silica (DFNS/TiO2) support. The DFNS/TiO2-Cu10 catalyst showed excellent catalytic performance with a CO productivity of 5350 mmol g-1 h-1 (i.e., 53,506 mmol gCu-1 h-1), surpassing that of almost all copper-based thermal catalysts, with 99.8% selectivity toward CO. Even after 200 h of reaction, the catalyst remained active. Moderate initial agglomeration and high dispersion of nanoparticles (NPs) due to SMSI made the catalysts stable. Electron energy loss spectroscopy confirmed the strong interactions between copper NPs and the TiO2 surface, supported by in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy. The H2-temperature programmed reduction (TPR) study showed α, β, and γ H2-TPR signals, further confirming the presence of SMSI between Cu and TiO2. In situ Raman and UV-vis diffuse reflectance spectroscopy studies provided insights into the role of oxygen vacancies and Ti3+ centers, which were produced by hydrogen, then consumed by CO2, and then again regenerated by hydrogen. These continuous defect generation-regeneration processes during the progress of the reaction allowed long-term high catalytic activity and stability. The in situ studies and oxygen storage complete capacity indicated the key role of oxygen vacancies during catalysis. The in situ time-resolved Fourier transform infrared study provided an understanding of the formation of various reaction intermediates and their conversion to products with reaction time. Based on these observations, we have proposed a CO2 reduction mechanism, which follows a redox pathway assisted by hydrogen.