Continuous flow hydrothermal synthesis of rutile SnO2 nanoparticles: Exploration of pH and temperature effects

New Insights for High-Throughput CO2 Hydrogenation to High-Quality Fuel

In the case of CO2 thermal-catalytic hydrogenation, highly selective olefin generation and subsequent olefin secondary reactions to fuel hydrocarbons in an ultra-short residence time is a huge challenge, especially under industrially feasible conditions. Here, we report a pioneering synthetic process that achieves selective production of high-volume commercial gasoline with the assistance of fast response mechanism. In situ experiments and DFT calculations demonstrate that the designed NaFeGaZr presents exceptional carbiding prowess, and swiftly forms carbides even at extremely brief gas residence times, facilitating olefin production. The created successive hollow zeolite HZSM-5 further reinforces aromatization of olefin diffused from NaFeGaZr via optimized mass transfer in the hollow channel of zeolite. Benefiting from its rapid response mechanism within the multifunctional catalytic system, this catalyst effectively prevents the excessive hydrogenation of intermediates and controls the swift conversion of intermediates into aromatics, even in high-throughput settings. This enables a rapid one-step synthesis of high-quality gasoline-range hydrocarbons without any post-treatment, with high commercial product compatibility and space-time yield up to 0.9 kggasoline ⋅ kgcat -1 ⋅ h-1. These findings from the current work can provide a shed for the preparation of efficient catalysts and in-depth understanding of C1 catalysis in industrial level.

Nanostructured electroless Ni deposited SnO2 for solar hydrogen production

Herein, Ni-decorated SnO2 (Ni@SnO2) nanostructures have been synthesized using SnO2 as a matrix via a simple electroless deposition method for the generation of hydrogen, a potent near-future fuel. XRD analysis confirmed the generation of rutile SnO2 in Ni@SnO2. FESEM and FETEM imaging exhibited the formation of SnO2 nanoparticles with a size of 10-50 nm, which are deposited with Ni nanoparticles (5-7 nm) and intermittent films (thickness 1-2 nm). The associated EDS elemental mapping validated Ni deposition on the surface of the SnO2 nanoparticles, further supplemented by FTIR, Raman and XPS analysis. Slight red shifts in the band gaps of the Ni@SnO2 nanostructures (in the range of 3.53-3.65 eV) compared to the pristine SnO2 nanoparticles (3.72 eV) were observed. Also, intensity quenching of the band gap and associated defect peaks were observed in PL analysis. The Ni@SnO2 nanostructures were used as photocatalysts and exhibited proficient hydrogen evolution. Among the samples, the 0.3 wt% Ni@SnO2 nanostructures showed the greatest hydrogen evolution, i.e., ∼50 μmol g-1 h-1 under visible light irradiation versus pristine SnO2 (8.5 μmol g-1 h-1) owing to the enhanced density of active sites and effective charge separation. It is noteworthy that the hydrogen evolution is much better as compared to earlier reports of Pt-doped-SnO2 based materials.

Continuous-Flow Synthesis of Zn1-xMnxS Nanoparticles at Ambient Conditions

With its large direct band gap and good chemical stability, ZnS is suitable for many applications, including light-emitting diodes, panel displays, and photodetection. Here, nanoparticles of ZnS are synthesized phase pure under ambient conditions by precipitation in a simple and scalable continuous-flow reactor. Furthermore, different degrees of Zn substitution with Mn have been investigated, Zn1-xMnxS, with x = 0.05, 0.19, and 0.25 according to X-ray fluorescence measurements. The products are analyzed with multitemperature synchrotron powder X-ray diffraction (PXRD) and X-ray total scattering. The analysis reveals phase-pure synthesis products with the sphalerite structure and crystallite sizes in the range of 3.8-4.7 nm in agreement with scanning transmission electron microscopy. Only Zn0.75Mn0.25S shows traces of Mn3O4, indicating that x = 0.25 is above the substitution limit as the impurity appears. Substitution of Zn with Mn in the nanoparticles is confirmed by energy-dispersive X-ray spectroscopy, as well as an observed decrease in the band gap, decrease in the sphalerite-to-wurtzite phase transition temperature, and increase in the unit cell dimensions with increasing Mn content. Based on the modeling of the PXRD Rietveld refined atomic displacement parameters, the Debye temperature for ZnS and Zn0.95Mn0.05S is determined to be 322 ± 13 and 394 ± 22 K, respectively.

The Impact of Co Doping and Annealing Temperature on the Electrochemical Performance and Structural Characteristics of SnO2 Nanoparticulate Photoanodes

Obtaining H₂ energy from H₂O using the most abundant solar radiation is an outstanding approach to zero pollution. This work focuses on studying the effect of Co doping and calcination on the structure, morphology, and optical properties of spin-coated SnO₂ films as well as their photoelectrochemical (PEC) efficiency. The structures and morphologies of the films were investigated by XRD, AFM, and Raman spectra. The results confirmed the preparation of SnO₂ of the rutile phase, with crystallite sizes in the range of 18.4-29.2 nm. AFM showed the granular structure and smooth surfaces having limited roughness. UV-Vis spectroscopy showed that the absorption spectra depend on the calcination temperature and the Co content, and the films have optical bandgap (E_g) in the range of 3.67-3.93 eV. The prepared samples were applied for the PEC hydrogen generation after optimizing the sample doping ratio, using electrolyte (HCl, Na₂SO₄, NaOH), electrode reusability, applied temperature, and monochromatic illumination. Additionally, the electrode stability, thermodynamic parameters, conversion efficiency, number of hydrogen moles, and PEC impedance were evaluated and discussed, while the SnO₂ films were used as working electrodes and platinum sheet as an auxiliary or counter electrode (2-electrode system) and both were dipped in the electrolyte. The highest photocurrent (21.25 mA/cm²), number of hydrogen moles (20.4 mmol/h.cm²), incident photon-to-current change efficiency (6.892%@307 nm and +1 V), and the absorbed photon-to-current conversion efficiency (4.61% at ~500 nm and +1 V) were recorded for the 2.5% Co-doped SnO₂ photoanode that annealed at 673 K.

Microwave-assisted continuous flow phytosynthesis of silver nanoparticle/reduced graphene oxide composites and related visible light catalytic performance

The creation of an environmentally friendly synthesis method for silver nanomaterials (AgNPs) is an urgent concern for sustainable nanotechnology development. In the present study, a novel straightforward and green method for the preparation of silver nanoparticle/reduced graphene oxide (AgNP/rGO) composites was successfully developed through the combination of phytosynthesis, continuous flow synthesis and microwave-assistance. Oriental persimmon (Diospyros kaki Thunb.) extracts were used as both plant reducing and capping agents for fast online synthesis of AgNP/rGO composites. The experimental parameters were optimized and the morphologies of the prepared materials were investigated. The characterization results reveal that spherical AgNPs were quickly synthesized and uniformly dispersed on rGO sheets using the proposed online system. Fourier transform infrared spectroscopy analysis confirmed that phenols, flavonoids, and other substances in the plant extracts played a decisive role in the synthesis of AgNP/rGO composites. Using sodium borohydride (NaBH₄) degradation of p-nitrophenol (4-NP) as a model, the catalytic activity of the prepared AgNP/rGO materials was evaluated. The complete degradation of 4-NP was achieved within 12 min through the use of AgNP/rGO materials, and the composite had a much better catalytic activity than the bare AgNPs and rGO had. Compared with the conventional chemical method, our online method is facile, fast, cost-efficient, and environmentally friendly.

Kasmani R, Kasim H, Al-Ghaili AM, Saleh MA, Banoqitah EM, Alhawsawi AM, Baqer AA, Liu J, Xu S, Li Q, Noorazlan AM, Ahmed AAA, Flaifel MH, Paiman S, Nazrin N, Ali Al-Asbahi B, Wang J. The Effect of Precursor Concentration on the Particle Size, Crystal Size, and Optical Energy Gap of CexSn1-xO2 Nanofabrication

In the present work, a thermal treatment technique is applied for the synthesis of Ce_xSn_1-xO₂ nanoparticles. Using this method has developed understanding of how lower and higher precursor values affect the morphology, structure, and optical properties of Ce_xSn_1-xO₂ nanoparticles. Ce_xSn_1-xO₂ nanoparticle synthesis involves a reaction between cerium and tin sources, namely, cerium nitrate hexahydrate and tin (II) chloride dihydrate, respectively, and the capping agent, polyvinylpyrrolidone (PVP). The findings indicate that lower x values yield smaller particle size with a higher energy band gap, while higher x values yield a larger particle size with a smaller energy band gap. Thus, products with lower x values may be suitable for antibacterial activity applications as smaller particles can diffuse through the cell wall faster, while products with higher x values may be suitable for solar cell energy applications as more electrons can be generated at larger particle sizes. The synthesized samples were profiled via a number of methods, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). As revealed by the XRD pattern analysis, the Ce_xSn_1-xO₂ nanoparticles formed after calcination reflect the cubic fluorite structure and cassiterite-type tetragonal structure of Ce_xSn_1-xO₂ nanoparticles. Meanwhile, using FT-IR analysis, Ce-O and Sn-O were confirmed as the primary bonds of ready Ce_xSn_1-xO₂ nanoparticle samples, whilst TEM analysis highlighted that the average particle size was in the range 6-21 nm as the precursor concentration (Ce(NO₃)₃·6H₂O) increased from 0.00 to 1.00. Moreover, the diffuse UV-visible reflectance spectra used to determine the optical band gap based on the Kubelka-Munk equation showed that an increase in x value has caused a decrease in the energy band gap and vice versa.