Vanadia as an electron-hole recombination inhibitor on fibrous silica-titania for selective hole oxidation of ciprofloxacin and Congo red photodegradation

Vanadia (V2O5)-incorporated fibrous silica-titania (V/FST) catalysts, which were successfully synthesized using a hydrothermal method followed by the impregnation of V2O5. The catalysts were then characterized using numerous techniques, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption analyses, ultraviolet-visible diffuse reflectance spectroscopy, Fourier-transform infrared, X-ray photoelectron spectroscopy, and photoluminescence (PL) analyses. The study found that varying the amount of V2O5 (1-10 wt%) had a significant impact on the physicochemical properties of the FST, which in turn improved the photodegradation efficiency of two organic compounds, ciprofloxacin (CIP) and congo red (CR). 5V/FST demonstrated the best performance in degrading 10 mg L-1 of CIP (83%) and CR (100%) at pH 3 using 0.375 g L-1 catalyst under visible light irradiation within 180 min. The highest photoactivity of 5V/FST is mainly due to higher crystallinity and the highest number of V2O5-FST interactions. Furthermore, as demonstrated by PL analysis, the 5V/FST catalyst has the most significant impact on interfacial charge transfer and reduces electron-hole recombination. The photodegradation of both contaminants follows the Langmuir-Hinshelwood pseudo-first-order model, according to the kinetic study. The scavenger investigation demonstrated that hydroxyl radicals and holes dominated species in the system, indicating that the catalyst effectively generated reactive species for pollutant degradation. A possible mechanism was also identified for FST and 5V/FST. Interestingly, V2O5 acts as an electron-hole recombination inhibitor on FST for selective hole oxidation of ciprofloxacin and congo red photodegradation. Finally, the degradation efficiency of the catalyst remained relatively stable even after five cyclic experiments, indicating its potential for long-term use in environmental remediation.

Co-production of hydrogen and carbon nanotubes by catalytic cracking of waste cooking oil model compound over Ni-Cu/Al-KCC-1

Ni-Cu/Al-KCC-1 catalysts with different metal contents were prepared using fibrous nano-silica (Al-KCC-1) as a support. Field emission scanning electron microscopy observations showed that the spherical particle morphology and fibrous structure of the Al-KCC-1 were not changed after metal loading. Transmission electron microscopy images demonstrated that the introduction of copper improved the dispersion of the nickel, while X-ray diffraction and hydrogen temperature-programmed reduction confirmed the formation of a Ni-Cu alloy. The N₂-Brunauer-Emmett-Teller specific surface areas of the catalysts were in the range of 269-378 m²/g and the average pore diameters were 7.988-12.078 nm. These Ni-Cu/Al-KCC-1 catalysts were used to promote the cracking of waste cooking oil model compound (WCOMC) to produce H₂ and carbon nanotubes (CNTs), and the 10 wt% Ni-5 wt% Cu/Al-KCC-1 exhibited the highest catalytic activity. At a WCOMC flow rate of 0.04 mL/min and 750 °C, the instantaneous volume fraction of H₂ reached 49.8 vol% and the content of H₂ in the gaseous product was close to 71.4 vol%.

Effect of Ultrasonication Parameters on the Structural, Morphological, and Electrical Properties of Polypyrrole Nanoparticles and Optimization by Response Surface Methodology

Polypyrrole (PPy) nanoparticles are reliable conducting polymers with many industrial applications. Nevertheless, owing to disadvantages in structure and morphology, producing PPy with high electrical conductivity is challenging. In this study, a chemical oxidative polymerization-assisted ultra-sonication method was used to synthesize PPy with high conductivity. The influence of critical sonication parameters such as time and power on the structure, morphology, and electrical properties was examined using response surface methodology. Various analyses such as SEM, FTIR, DSC, and TGA were performed on the PPy. An R² value of 0.8699 from the regression analysis suggested a fine correlation between the observed and predicted values of PPy conductivity. Using response surface plots and contour line diagrams, the optimum sonication time and sonication power were found to be 17 min and 24 W, respectively, generating a maximum conductivity of 2.334 S/cm. Meanwhile, the model predicted 2.249 S/cm conductivity, indicating successful alignment with the experimental data and incurring marginal error. SEM results demonstrated that the morphology of the particles was almost spherical, whereas the FTIR spectra indicated the presence of certain functional groups in the PPy. The obtained PPy with high conductivity can be a promising conducting material with various applications, such as in supercapacitors, sensors, and other smart electronic devices.

Promoting a well-dispersion of MoO3 nanoparticles on fibrous silica catalyst via one-pot synthesis for enhanced photoredox environmental pollutants efficiency

The coexistence of pharmaceutical compounds and heavy metals in the aquatic environment has resulted in complications in the treatment process and thus, causing uproar among the citizens. The radical-based photocatalysis technology has aroused as an excellent method to eliminate both heavy metal and pharmaceutical compounds in the water. Herein, reported the utilization of the microemulsion technique for the preparation of nanoporous fibrous silica-molybdenum oxide (FSMo) towards simultaneous photocatalytic abatement of hexavalent chromium (Cr(VI)) and tetracycline (TC). The FESEM analysis showed the spherical morphology of the FSMo catalyst with dendrimeric silica fiber. The synthesized FSMo catalyst exhibited narrowed bandgap, high crystallinity, and well Mo element dispersion for enhanced photo-redox of Cr(VI) and TC. Remarkably, simultaneous remediation of the Cr(VI) and TC over FSMo demonstrated superior photocatalytic efficiency, 69% and 75%, respectively, than in the individual system, possibly due to the effective separation of photoinduced charges. The introduction of the Mo element to the silica framework via microemulsion technique demonstrated better dispersion of Mo compared to the incipient wetness impregnation method and thus, yielded higher photocatalytic activity towards simultaneous removal of TC and Cr(VI). Besides, quenching experiments revealed the electrons and holes as the active species that play a dominant role in the simultaneous photo-redox of Cr(VI) and TC. Lastly, the FSMo catalyst demonstrated high stability after four continuous cycles of simultaneous photocatalysis reactions, implying its potential as a suitable material for practical wastewater treatments.

Ni-Based Catalyst for Carbon Dioxide Methanation: A Review on Performance and Progress

Catalytic conversion of CO2 into methane is an attractive method because it can alleviate global warming and provide a solution for the energy depletion crisis. Nickel-based catalysts were commonly employed in such conversions due to their high performance over cost ratio. However, the major challenges are that Ni tends to agglomerate and cause carbon deposition during the high-temperature reaction. In the past decades, extensive works have been carried out to design and synthesize more active nickel-based catalysts to achieve high CO2 conversion and CH4 selectivity. This review critically discusses the recent application of Ni-based catalyst for CO2 methanation, including the progress on the effect of supporting material, promoters, and catalyst composition. The thermodynamics, kinetics, and mechanism of CO2 methanation are also briefly addressed.

Co-Precipitated Ni-Mg-Al Hydrotalcite-Derived Catalyst Promoted with Vanadium for CO2 Methanation

Co-precipitated Ni-Mg-Al hydrotalcite-derived catalyst promoted with vanadium were synthesized with different V loadings (0–4 wt%) and studied in CO₂ methanation. The promotion with V significantly changes textural properties (specific surface area and mesoporosity) and improves the dispersion of nickel. Moreover, the vanadium promotion strongly influences the surface basicity by increasing the total number of basic sites. An optimal loading of 2 wt% leads to the highest activity in CO₂ methanation, which is directly correlated with specific surface area, as well as the basic properties of the studied catalysts.

Enhanced CO2 methanation at mild temperature on Ni/zeolite from kaolin: effect of metal-support interface

Catalytic CO₂ hydrogenation to CH₄ offers a viable route for CO₂ conversion into carbon feedstock. The research aimed to enhance CO₂ conversion at low temperature and to increase the stability of Ni catalysts using zeolite as a support. NaZSM-5 (MFI), NaA (LTA), NaY (FAU), and NaBEA (BEA) synthesized from kaolin were impregnated with 15% Ni nanoparticles in order to elucidate the effect of surface area, porosity and basicity of the zeolite in increasing Ni activity at mild temperature of ∼200 °C. A highly dispersed Ni catalyst was produced on high surface area NaY meanwhile the mesoporosity of ZSM-5 has no significant effect in improving Ni dispersion. However, the important role of zeolite mesoporosity was observed on the stability of the catalyst. Premature deactivation of Ni/NaA within 10 h was due to the relatively small micropore size that restricted the CO₂ diffusion, meanwhile Ni/NaZSM-5 with a large mesopore size exhibited catalytic stability for 40 h of reaction. Zeolite NaY enhanced Ni activity at 200 °C to give 21% conversion with 100% CH₄ selectivity. In situ FTIR analysis showed the formation of hydrogen carbonate species and formate intermediates at low temperatures on Ni/NaY, which implied the efficiency of electron transfer from the basic sites of NaY during CO₂ reduction. The combination of Ni/NaY interfacial interaction and NaY surface basicity promoted CO₂ methanation reaction at low temperature.

Different Na-zeolites as supports of Ni metal were successfully synthesized from kaolin-based material. Combination of interfacial interaction Ni-support and surface basicity promoted CO₂ methanation reaction at a low temperature of ∼200 °C.

CO2 Hydrogenation to Methane over Ni-Catalysts: The Effect of Support and Vanadia Promoting

Within the Waste2Fuel project, innovative, high-performance, and cost-effective fuel production methods are developed to target the “closed carbon cycle”. The catalysts supported on different metal oxides were characterized by XRD, XPS, Raman, UV-Vis, temperature-programmed techniques; then, they were tested in CO2 hydrogenation at 1 bar. Moreover, the V2O5 promotion was studied for Ni/Al2O3 catalyst. The precisely designed hydrotalcite-derived catalyst and vanadia-promoted Ni-catalysts deliver exceptional conversions for the studied processes, presenting high durability and selectivity, outperforming the best-known catalysts. The equilibrium conversion was reached at temperatures around 623 K, with the primary product of reaction CH4 (>97% CH4 yield). Although the Ni loading in hydrotalcite-derived NiWP is lower by more than 40%, compared to reference NiR catalyst and available commercial samples, the activity increases for this sample, reaching almost equilibrium values (GHSV = 1.2 × 104 h–1, 1 atm, and 293 K).