SnO2 Catalysts Research Articles

Characteristics of textile waste water of Bhilwara (Rajasthan) and its photocatalytic bleaching with SnO2 catalyst

During the last decade, Bhilwara has developed into a leading place in the textile industry in India. The water used in textile industry is almost entirely discharged as waste. The effluents are very complex, containing salt, surfactants, ionic metals and their metal complexes, toxic organic chemicals, biocides, and toxic anions, which are harmful to both flora and fauna existing on our planet. Degradation of these non-biodegradable organic compounds is not possible by conventional treatment processes. The analysis of waste water with different quality parameters and photocatalytic bleaching was examined by using UV light in photochemical reactor with SnO2 catalyst.

Controllably Engineering Mesoporous Surface and Dimensionality of SnO2 toward High‐Performance CO2 Electroreduction

AbstractCurrently, the precise control of the architecture and surface of functional materials for high‐performance still remains a great challenge. Here, a feasible approach is presented to synchronously manipulate mesoporous surface and dimensionality of SnO2 catalysts into hierarchically mesoporous nanosheets and nanospheres within one simple reaction system. By adjustment of the hydrophobic chain length of different fluorinated surfactants, 0D SnO2 nanospheres with average size of 165 nm, and 2D SnO2 ulthrathin nanosheets with thickness of 22.5 nm with the distinct dimensionalities are separately obtained (one stone, two birds), both of which are well decorated with ordered mesopore arrays on their surfaces (pore size of 16 nm). The following calcination gave rise to the formation of hierarchically mesopores (5 and 16 nm, respectively) with high crystallization and improved surface area (96.8 m2 g−1). The resultant mesoporous SnO2 nanosheets as catalyst for CO2 electroreduction reaction (CO2 RR) exhibit excellent selectivity, with a high Faraday efficiency (FE) of HCOOH reaching up to 90.0% at −1.3 V and C1 FE of 97.4% at −1.2 V versus reversible hydrogen electrode, as well as long‐term stability, which is among the best performance compared to reported SnO2 materials, thanks to the collective contributions of the unique architecture and mesoporous structure.

Recent Advances in Nanoarchitectonics of SnO₂ Clusters and Their Applications in Catalysis.

Tin dioxide nanoclusters are very effective as catalysts for various reactions including CO₂ conversion and Friedel-Crafts acylation for pharmaceuticals. The nanoarchitectonics of SnO₂ could be controlled by different synthetic strategies. In the current article, we have presented synthesis of SnO₂ nanoclusters and their applications in catalysis. We have also reviewed computational studies on SnO₂ nanoclusters for using them in nanoarchitectonics and catalytic conversion of CO₂ to useful chemicals. Optimized structures of various cluster sizes are presented. The present and future perspectives of SnO₂ catalysts in biomass conversions are also given.

SnO2 particles as efficient photocatalysts for organic dye degradation grown in-situ on g-C3N4 nanosheets by microwave-assisted hydrothermal method

In this work, SnO2 nanoparticles (NPs) were grown in-situ on g-C3N4 nanosheets using a microwave-assisted hydrothermal method. The resulting nanocomposite formed heterojunctions with useful photocatalytic properties. The morphology and chemical structure of the g-C3N4/SnO2 were thoroughly characterized. UV–vis and photoluminescence results revealed g-C3N4/SnO2 heterojunction with strong light adsorption and enhanced efficient separation of electron-hole pairs, respectively. These properties provided an excellent photocatalytic efficiency of the g-C3N4/SnO2 catalysts towards Rhodamine B degradation under UV and visible light irradiation, which were 100% and 98.5%, respectively, after 4 h of exposure to light. Such efficient materials could be used for future degradation of organic dyes under solar light. In addition, these composite materials could be applied to environmentally friendly photocatalysis reaction.

It Is Time to Think about Scale

While the electrochemical reduction of carbon dioxide (CO2) to valuable products has been studied for over three decades, the dream of scaling up the process remains. Recently in ACS Energy Letters, Neyerlin and co-workers take a large step forward in establishing a platform to synthesize formate from CO2 at scale.

Solvent-Free Production of Glycerol Carbonate from Bioglycerol with Urea Over Nanostructured Promoted SnO2 Catalysts

In this study nanostructured MoO3 and WO3 promoted SnO2 solid acid catalysts were explored for the production of glycerol carbonate via carbonylation of bioglycerol with urea. The investigated reference SnO2 and promoted catalysts were synthesized by fusion and wet-impregnation methods, respectively. The physicochemical properties of the prepared catalysts were thoroughly analyzed by XRD, Raman, BET surface area, TEM, FTIR, pyridine adsorbed FTIR, NH3-TPD, and XPS techniques. It was found from the characterization studies that integration of SnO2 with MoO3 and WO3 promoters leads to remarkable structural, textural, and acidic properties. Especially, a high quantity of acidic sites were observed over the MoO3/SnO2 catalyst (~ 81.45 μmol g−1) followed by WO3/SnO2 (61.81 μmol g−1) and pure SnO2 (46.47 μmol g−1), which played a key role in the carbonylation of bioglycerol with urea. The BET specific surface area and oxygen vacancies of SnO2 were significantly enhanced after the addition of MoO3 and WO3 promoters. TEM images revealed the formation of nanosized particles with a diameter of around 5–25 nm for the synthesized catalysts. The MoO3/SnO2 catalyst exhibited a high conversion and selectivity towards glycerol carbonate in comparison to other catalysts. The observed better performance is attributed to unique properties of MoO3/SnO2 catalyst including smaller crystallite size, high specific surface area, abundant oxygen vacancies, and more number of acidic sites. This catalyst also exhibited remarkable stability with no significant loss of activity in the recycling experiments. Nanostructured MoO3/SnO2 solid acid catalyst exhibited an excellent catalytic activity and a high selectivity to glycerol carbonate in the carbonylation of bioglycerol with urea under solvent-free and mild conditions.

Catalytic Conversion of Glucose to 5-Hydroxymethylfurfural and Furfural by a Phosphate-Doped SnO2 Catalyst in γ-Valerolactone-Water System

5-Hydroxymethylfurfural (5-HMF) and furfural are produced from glucose by using a novel phosphate-doped SnO2 catalyst in GVL/water system. Comparing with the low yield (19.3% 5-HMF, 7.2% furfural) of SnO2 as catalyst, the loading of 15 wt% phosphate on the SnO2 can enhance the yield of 5-HMF (39.2%) and furfural (12.5%) from glucose under same reaction conditions. Furthermore, under the optimal conditions, the results indicate that the phosphated SnO2 catalyst, which contains 5 wt% phosphate, can result in 46.4% yield of 5-HMF and 18.9% yield of furfural at 180 °C for 90 min. The phosphated SnO2 catalysts are characterized by using XRD, TEM, Py-IR, XPS and TPD to reveal their structural, surface, and acid properties. And the enhanced 5-HMF and furfural yield could be attributed to the higher acidity, and the incorporation of phosphate into the framework of SnO2.

Improved photocatalytic performance of nanostructured SnO2 via addition of alkaline earth metals (Ba2+, Ca2+ and Mg2+) under visible light irradiation

Pure and alkaline earth metal (Ba2+, Ca2+ and Mg2+)-doped tin oxide nanoparticles were synthesized by simple co-precipitation, and their structural, optical, functional, morphological and compositional properties were analyzed in detail using powder X-ray diffraction, UV–visible spectroscopy, photoluminescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and energy-dispersive analysis of X-ray (EDAX). XRD revealed the formation of rutile tetragonal structure, and the crystallite size has decreased from 28 to 24 nm by the addition of alkaline metal dopants. FTIR spectra confirmed the presence of fundamental vibration modes of SnO2. The optical band gap energy was decreased to 3.05, 3.19 and 2.98 eV by introducing Ba2+, Ca2+ and Mg2+ ions, respectively. Photoluminescence spectra showed defect-related emission peaks, and their intensities were found to increase in doped SnO2 samples. EDAX spectra confirmed the presence of Sn, O, Ba, Ca and Mg elements. The photocatalytic activity of pure and alkaline metal-doped SnO2 catalyst has been investigated under visible light irradiation by using methylene blue dye. The results showed that the Mg-doped SnO2 catalyst has a higher photodegradation efficiency (~ 95.7%) compared with other investigated samples.

Surface chemistry of 2-propanol and O2 mixtures on SnO2(110) studied with ambient-pressure x-ray photoelectron spectroscopy.

Tin dioxide (SnO2) has various applications due to its unique surface and electronic properties. These properties are strongly influenced by Sn oxidation states and associated defect chemistries. Recently, the oxidation of volatile organic compounds (VOCs) into less harmful molecules has been demonstrated using SnO2 catalysts. A common VOC, 2-propanol (isopropyl alcohol, IPA), has been used as a model compound to better understand SnO2 reaction kinetics. We have used ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) to characterize the surface chemistry of IPA and O2 mixtures on stoichiometric, unreconstructed SnO2(110)-(1 × 1) surfaces. AP-XPS experiments were performed for IPA pressures ≤3 mbar, various IPA/O2 ratios, and several reaction temperatures. These measurements allowed us to determine the chemical states of adsorbed species on SnO2(110)-(1 × 1) under numerous experimental conditions. We found that both the IPA/O2 ratio and sample temperature strongly influence reaction chemistries. AP-XPS valence-band spectra indicate that the surface was partially reduced from Sn4+ to Sn2+ during reactions with IPA. In situ mass spectrometry and gas-phase AP-XPS results indicate that the main reaction product was acetone under these conditions. For O2 and IPA mixtures, the reaction kinetics substantially increased and the surface remained solely Sn4+. We believe that O2 replenished surface oxygen vacancies and that SnO2 bridging and in-plane oxygen are likely the active oxygen species. Moreover, addition of O2 to the reaction results in a reduction in formation of acetone and an increase in formation of CO2 and H2O. Based on these studies, we have developed a reaction model that describes the catalytic oxidation of IPA on stoichiometric SnO2(110)-(1 × 1) surfaces.

Surface plasmon resonance effect of Ag metallized SnO2 particles: Exploration of metal induced gap states and characteristic properties of Ohmic junction

Ag metallization on the surface of SnO2 catalyst was performed by the photoreduction method, and its presence was confirmed by the (111), (200), (220), and (311) hkl planes of Ag metal by powder X‐ray diffraction technique. Further lattice parameters “a” and “c” of the SnO2 tetragonal unit cell show prominent changes on metallization. Ultraiolet‐visible absorption spectrum of Ag‐SnO2 shows the extended adsorption in the visible region up to almost ~565 nm due to the surface plasmon resonance (SPR) effect. Percentage composition of the elements present in the SnO2 and Ag‐SnO2 samples were confirmed by the energy‐dispersive X‐ray analysis and the inductively coupled plasma‐atomic emission spectroscopic analysis techniques, and the spherical morphology of these samples were confirmed by the scanning electron microscopy. The photoluminescence technique confirms the reduction of recombination of photogenerated charge carriers by 44% in the case of Ag‐SnO2. The metal‐metal oxide contact was found to be Ohmic rather than Schottky. The higher activity of the Ag‐SnO2 nanoparticles are correlated to the SPR effect, metal‐induced gap states, inherently created structural defects, the ability of Sn to show multiple oxidation states, variation in the surface oxygen concentration, and also to the Ohmic junction. Synergistic effect between electronic/intrinsic defect energy levels of Ag‐SnO2 photocatalyst with the redox potential of the fast red dye leads to the higher quantum efficiency.

Growth of Carbon Nanocoils by Porous \u03b1-Fe2O3/SnO2 Catalyst and Its Buckypaper for High Efficient Adsorption

HighlightsHigh-purity (~ 99%) carbon nanocoils (CNCs) without the amorphous carbon layer were synthesized by using porous α-Fe2O3/SnO2 catalyst.The highest yield of the CNCs can reach ~ 9098% after a 6 h growth, which is much higher than those mentioned in previous reports.A CNC Buckypaper was successfully prepared and utilized as an efficient adsorbent for the removal of methylene blue dye with the adsorption efficiency of 90.9%.

Surface structure-dependent electrocatalytic reduction of CO2 to C1 products on SnO2 catalysts

Surface structure-dependent electrocatalytic reduction of CO2 to C1 products on SnO2 catalysts was attributed to the in situ formation of different Sn/SnO2 catalytic layers on their surfaces.

Preparation and characterization of SiO2 nanowires using a SnO2 catalyst

SiO2 nanowires have been successfully synthesized on the surface of the silicon substrate via a thermal evaporation method using SnO2 powders as the catalysts. The final synthesized product was systematically studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), and electron energy dispersive X-ray (EDX), UV-Visible absorption and photoluminescence (PL) spectroscopy. The results reveal that in the reaction and growth process, the real catalytic effect is Sn and SnOx, and the growth of SiO2 nanowire is most likely controlled by VLS mechanism. The PL spectral results indicate the obtained products have a stable yellow-green emission range. The products have improved performance and can be used in optoelectronic semiconductor devices.

Sulfated Tin Oxide as Highly Selective Catalyst for the Chlorination of Methane to Methyl Chloride

The chlorination of methane (CH4) is an attractive route to convert CH4 into more valuable chemicals. The selective formation of methyl chloride (CH3Cl) is a key process, but it is rather difficult to achieve with high selectivity due to a radical reaction. Catalytic ionic processes can be a solution. Herein, sulfated tin oxide (STO) was employed in the gas-phase catalytic chlorination of CH4. The STO catalyst exhibited high selectivity to CH3Cl (>96%) even at high CH4 conversion. By applying a suite of physicochemical characterizations, it is shown that the strong Lewis acid sites on STO generated by the interaction of Sn and surface sulfate groups are mainly responsible for the highly selective CH4 conversion. DFT calculations further revealed that STO surface can activate more Cl2 molecules in a heterolytic manner, leading to better catalytic performances as compared to SnO2 and sulfated zirconia catalysts.

Function promotion of SO42−/Al2O3–SnO2 catalyst for biodiesel production from sewage sludge

Catalysts are critical materials for biodiesel production using sewage sludge feedstock. In this research, different SO42−/Al2O3–SnO2 catalysts were prepared and characterized. The catalysts prepared at different conditions were characterized through Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), NH3-temperature-programmed desorption (NH3-TPD), NH3 adsorption FT-IR, and TGA. Then, esterification/transesterification reaction was performed with the lipid extracted from sewage sludge to verify the activity of these catalysts. Results showed that the catalysts with n(Al):n(Sn) = 1:10 prepared by 79 wt% H2SO4 possessed the best physical properties with a large number of active catalytic sites, which led to the biodiesel yield of 73.3% (based on dried extracted crude fat) under the optimized reaction conditions at 130 °C as reaction temperature, 0.8 g as catalyst loading for lipids extracted from 10 g freeze-dried sludge, 4 h as reaction time. Catalysts characterization results showed that acidity, acid sites and Al/Sn molar ratio play an important role in the activity of catalysts. The thermal properties showed that 450 °C was the suitable calcination temperature for catalyst preparation. The optimized SO42−/Al2O3–SnO2 catalyst in this research will have a bright future in the field of sludge production of biodiesel.

Deactivation mechanism and anti-deactivation modification of SnO2-based catalysts for methane gas sensors

Hexamethyldisiloxane (HMDSO) is one of the most serious poisons in the field of catalysts. In this research, the deactivation of SnO2 and Pd/SnO2 catalysts by HMDSO was studied. Surface modification with Ag/Al2O3 was used to improve the resistance of the catalyst to HMDSO deactivation. To intrinsically investigate the deactivation mechanism of the catalyst, the morphology, structure and surface state of the catalyst were characterized by SEM, EDS, HRTEM, XPS, Raman, and PL. HMDSO decomposed on the SnO2 catalyst surface, yielding organosilicon and silicates (SixOy, y/x<2). On the surface of the Pd/SnO2, in addition to the organosilicon and silicates, the decomposition products of HMDSO also contained SiO2. SixOy can be further oxidized at highly active sites associated with bridging OVs on the Pd/SnO2 surface, forming SiO2. With the decomposition of HMDSO on the surfaces of the SnO2 and Pd/SnO2 catalysts, the reduction in OVs and clogging of the pores led to irreversible deactivation of the catalysts for CH4 detection. However, for the Pd/SnO2 catalyst surface-modified by Ag/Al2O3, deactivation by HMDSO exposure was reversible. HMDSO decomposed on the surface of the Ag and Al2O3 support. In addition, Al2O3 acts as a filter layer which prevent the penetration of HMDSO and its decomposition products. Therefore, the inner sensing layer was protected by the surface-modification layer from HMDSO deactivation.

A novel high-performance SnO2 catalyst for oxidative desulfurization under mild conditions

The catalyst SnO2 was prepared by a precipitation method, and then aged and calcined at the optimal temperature of 673 K. The reaction conditions were optimized and the oxidation desulfurization efficiency of the obtained catalyst were evaluated. The sulfur removal rate was 99.8% at the optimum reaction conditions of 0.08 g catalyst, 333 K, O/S = 10, 2 h. The catalytic site in the ODS process of the SnO2 catalyst may be Sn4+/Sn2+ Lewis acids. Furthermore, no significant catalytic performance decrease was observed over 14 reuse cycles. The excellent activity and reusability of the catalyst was attributed to the beneficial effects upon specific surface area and acidic-site strength of the appropriate heat treatment temperature.

Theory assisted design of N-doped tin oxides for enhanced electrochemical CO2 activation and reduction

Clearly understanding the structure-function relationship and rational design of efficient CO2 electrocatalysts are still the challenges. This article describes the molecular origin of high selectivity of formic acid on N-doped SnO2 nanoparticles, which obtained via thermal treatment of g-C3N4 and SnCl2·2H2O precursor. Combined with density functional theory (DFT) calculations, we discover that N-doping effectively introduces oxygen vacancies and increases the charge density of Sn sites, which plays a positive role in CO2 activation. In addition, N-doping further regulates the adsorption energy of *OCHO, *COOH, *H and promotes HCOOH generation. Benefited from above modulation, the obtained N-doped SnO2 catalysts with oxygen vacancies (Ov-N-SnO2) exhibit faradaic efficiency of 93% for C1 formation, 88% for HCOOH production and well-suppression of H2 evolution over a wide range of potentials.

A Rational Design of Cu2O−SnO2 Core‐Shell Catalyst for Highly Selective CO2‐to‐CO Conversion

AbstractThe electrochemical reduction of CO2 (CO2RR) is a versatile method that is capable of simultaneously reduce CO2 emission and produce valuable fuels and chemicals. However, its application is hindered by the lack of cost‐effective catalysts and significant overpotential requirement. In this work, we report a low‐cost and surfactant/capping agent free method to synthesize cubic Cu2O−SnO2 core‐shell electrocatalyst, whose thickness can be easily controlled by the content of tin precursor. The optimized Cu2O−SnO2 catalyst with a 5 nm‐thick shell achieved over 90 % faradaic efficiency towards CO at a low overpotential of 390 mV, which is comparable to some of the noble metal catalysts. The catalyst also exhibited good stability over 18 hours of test at −0.6 V vs. RHE in 0.5 M KHCO3 electrolyte. This work provides a widely applicable strategy for developing a low‐cost electrocatalyst for CO2 conversion.

TiO2, SnO2 and ZnO catalysts supported on mesoporous SBA-15 versus unsupported nanopowders in photocatalytic degradation of methylene blue

Abstract Semiconductor metal oxides (TiO2, ZnO or SnO2) deposited on a highly ordered mesoporous silica material (called SBA-15 in the literature) were compared for the first time as photocatalysts in the elimination of cationic methylene blue (MB) dye from neutral aqueous solutions by adsorption and/or photodegradation under ultraviolet (UV) irradiation. Prepared catalysts were characterized by N2 physisorption, X-ray diffraction, UV–visible diffuse reflectance spectroscopy, ammonia temperature-programmed desorption, isoelectric point determination, scanning and transmission electron microscopy. Characterization results showed that the mesoporous structure of the SBA-15 was preserved in the catalysts. However, the dispersion of metal oxides in the catalysts was very different. Zinc oxide was well-dispersed in the ZnO/SBA-15 catalyst, whereas TiO2 and SnO2 crystalline phases were detected in the TiO2/SBA-15 and SnO2/SBA-15 samples, being SnO2 oxide the worst-dispersed. All SBA-15-supported catalysts showed high capacity for MB adsorption, especially the ZnO/SBA-15 one, and had a significantly higher (2–5 times) photocatalytic activity than the corresponding commercial TiO2, ZnO and SnO2 nanopowders. The TiO2/SBA-15 and ZnO/SBA-15 catalysts resulted in a higher degree of mineralization of MB dye (63%) than titania Degussa P25 (39%) in the photocatalytic degradation of MB after the adsorption step. This was attributed to the higher specific surface area of the SBA-15-supported catalysts, their higher adsorption capacity and better dispersion of the supported metal oxides in comparison with titania P25. In addition, deposition of ZnO on the SBA-15 surface prevented the photocorrosion of ZnO that is an important advantage compared to pure ZnO nanoparticles.