Sol-gel Preparation Research Articles

Influences on the structure, magnetic, and magnetocaloric effect of La0.8Sr0.2MnO3 ceramics by Co ion doping with sol-gel method and first-principles calculations

This paper investigated the impact of Co ions doping on the structure, magnetic properties, and magnetocaloric effect for La0.8Sr0.2Mn1-xCoxO3 ceramics (LSMCO) by sol-gel method and first-principles calculations The use of first-principles calculations was provided for subsequent experiments. The sol-gel preparation of LSMCO ceramics and sintered at 950 °C for 10 h. It was shown that the samples' cell volume and lattice constants changed slightly with increasing Co2+ doping but remained a rhombohedral structure (No.167, R-3c space group) by statistics of TEM and XRD. The average particle size for the LSMCO ceramics ranged from 130 nm to 170 nm. LSMCO's chemical composition was verified by EDS and XPS and it was demonstrated that Co2+ was successfully doped. The oxidation state of La was found to be +3, Mn is a mixture of Mn3+ and Mn4+ valence states, and Co is a mixture of Co3+ and Co2+ valence states using XPS. In the vicinity of Tc, all samples presented the second-order magnetic phase transition from ferromagnetic to paramagnetic resorting to normalization and the Banerjee criterion. The Tc dropped from 292 K to 237 K with increasing Co2+ doping. The blocking temperature and the saturation magnetization were suppressed by the Co2+ substitution while the maximum magnetic entropy change of the LSMCO ceramics was observed to reduce as Co2+ increased. When the external magnetic field is 5 T, the La0.8Sr0.2Mn0.95Co0.05O3 ceramics has a Tc of 292 K and a maximum magnetic entropy change value of 3.47 J/(kg K).

Synthesis, morphology and dosimetric properties of Cr3+ activated Ca2Al2SiO7 nanophosphor prepared via sol-gel route

In this study, the structural, morphological, photoluminescence (PL), and dosimetric properties of Ca2-xAl2SiO7: xCr3+, at various Cr3+ concentrations (0 ≤ x ≤ 1 mol%) have been studied. The phosphor material was synthesized via sol-gel route with an octadecylamine as a catalyst. The average crystallite sizes were estimated to be in the range 21–30 nm using the modified Scherrer method which are in good agreement with data yielded by TEM micrographs. The energy-dispersive X-ray (EDX) spectra with scanning electron microscope (SEM) data confirm the homogeneous existence, and distribution of constituent elements within the structure and approved the sol-gel preparation method. PL spectra shows that Cr3+ doped Ca2Al2SiO7 structure has shoulder broadening and maximum peaks maintained at 442 ± 3.0 and 491 ± 3.02 nm upon 337 nm excitation which caused by 4F (4A2→4T2), 4F (4A2→4T1), and 4P (4A2→4T1) electronic spin-allowed transitions. Thermoluminescenc (TL) sensitivity characteristics of the obtained samples were scrutinized using Co-60 γ-radiation source. Cr0.4 sample was found to be optimum and its TL intensity increases linearly with increasing γ-doses from 0.5 up to 10 Gy. An accuracy using relative standard deviation (RSD) calculations of the homogenous study for Cr0.4 was found to be 4.02% (<10%, accepted due to ISO rules). Threshold dose of Cr0.4 sample was computed to be about 258 μGy. Acquired results of photon attenuation parameters estimations of Ca2Al2SiO7 composition using Phy-X PSD online program show that this composition is a bone equivalent dosimeter. According to this article, Cr0.4 doped Ca2Al2SiO7 sample can be considered as useful TL-material in various dosimetric applications.

Researching the electrochemical performance by Mn2+ substituted Na3+xV2-xMnx(PO4)3/rGO cathode materials for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are gaining rising popularity as potential energy storage solutions for large-scale renewable energy, attributed to their affordable pricing and inherent safety features. The reversible capacity of AZIBs, which is crucial for their cycle performance, is significantly influenced by the choice of cathode material, with Na3V2(PO4)3 standing out as promising candidates for their large 3D transport channels and rapid kinetics. However, they suffer from rapid degradation caused by low structural stability during the charge-discharge process. In this work, we researched the electrochemical performance of cathode materials by employing a sol-gel preparation for Mn-doped Na3-xV2-xMnx(PO4)3/rGO (x = 0, 0.05, 0.1), in which graphene oxides (rGO) were introduced as carbon sources. It is identified that the Mn doping exerts a beneficial influence to enhance stability of the structure. The Mn0.05-NVP/rGO material, optimized for performance, exhibits a specific capacity of 106.3 mAh·g−1 with a discharge plateau at 1.3 V at a current density of 100 mA·g−1, which corresponds to an energy density of 134.7 Wh·kg−1. Particularly, the addition of Mn enhances cycling performance, leading to a remarkable capacity retention rate of 75.3 % even after 100 cycles. This work confirms the feasibility using NASICON-type cathodes and offers valuable perceptions into the advancement of cathode materials in AZIBs.

Optimization of sol-gel preparation method for Y0.9Ce0.1Mn3+δ to improve the oxygen storage properties

Optimization of sol-gel preparation method for Y0.9Ce0.1Mn3+δ to improve the oxygen storage properties

Promotion of Different Active Phases in MnOX-CeO2 Catalysts for Simultaneous NO Reduction and o-DCB Oxidation

AbstractMnOX-CeO2 catalysts with different Mn and Ce content were prepared to evaluate the effect of metal content on catalytic properties and activity in the simultaneous NO reduction and o-DCB oxidation, in order to elucidate the most active species for the process. Catalytic properties were evaluated by ICP-AES, XRD, skeletal FTIR, STEM-HAADF, XPS, N2-physisorption, H2-TPR, NH3-TPD and pyridine-FTIR. Catalysts with 85%Mn and 15%Ce molar content have been found to be the most active. Their excellent catalytic performance is related to the coexistence of Mn in different phases, i.e., Mn species strongly interacting with Ce and segregated Mn species. The effect of the preparation methods has also been deeply investigated: Co-precipitation method (CP) leads to Mn segregation as Mn2O3, whereas sol-gel preparation method (SG) promotes the formation of an amorphous powder. The synergy between segregated Mn2O3 species and Mn species in high interaction with Ce (resulting in a mixed oxide phase) leads to the presence of Mn with different oxidation states. This effect, together with the high oxygen mobility caused by structural defects, enhances redox, acidic and oxidative properties. The improvement of catalytic properties with Mn content also favors NO reduction side-reactions, with N2O and NO2 being the most important by-products, whereas it limits the production of chlorinated organic by-products in o-DCB oxidation.

Research on ballistic performance of green shear thickening functionalized fabric based on solid waste modification

Based on the solid waste-based modification, green shear-thickening functionalized ballistic composites were prepared. Silica aerosols were obtained from solid waste diatomaceous earth through sol–gel preparation, gel aging, and supercritical drying. The modified silica aerosols acted as the dispersed phase, regulating the green shear-thickening liquid. A comparison was made between the performance of the modified shear-thickening liquid (SG@STF) and traditional shear-thickening liquids. By modifying solid waste based shear thickener (SG@STF) Combined with aramid fabric (AF) to test Ballistic performance. Characterization tests revealed that the rheological properties of SG@STF were significantly enhanced by increasing the volume fraction of the dispersed phase in STF from 50 % to 60 %. This enhancement was attributed to the addition of reactive functional groups on the surface of the silica sol. Yarn pull-out tests demonstrated that SG@STF/AF improved the tensile strength by 120 % compared to AF fabric, thanks to its superior friction properties. Ballistic tests showed that SG@STF increased the ballistic ultimate velocity of AF fabric by 105 %, elevating AF’s ballistic limiting velocity from 51 m/s to 105 m/s. Consequently, SG@STF/AF exhibited superior ballistic properties compared to AF fabric. The doping of SG enhanced the friction between yarns and increased the load-bearing area of the fabrics, thereby improving the ballistic properties of SG@STF/AF and achieving the desired modulation of their ballistic properties.

Investigating grain and grain boundary effects on charge transport and dielectrics in BaCoxAlxFe12-2xO19 nanoferrites

This investigation centres on the sol-gel preparation of M-type barium hexagonal ferrite (M-BaFe12O19) incorporating Co2+ and Al3+ as dopants. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were employed to assess the impact of dopants on the crystallographic structure and microstructure. The dielectric characteristics, electric modulus, impedance, and conductivity of the synthesized materials were evaluated at ambient temperature using an impedance analyzer. The structural analysis verified the presence of the hexagonal M-type crystal phase. Increasing dopant levels led to a reduction in lattice parameters, signifying unit cell shrinkage. FESEM imaging exposed the emergence of needle-shaped grains resulting from the doping process. Dielectric spectroscopy showed a decrease in both the dielectric constant (from 135.95 at x = 0.0 to 39.8) and the loss tangent (from 3.68 to 0.610) as dopant concentration increased. Conductivity exhibited relaxation at varying intervals, supported by the electric modulus spectra, which validated non-Debye relaxation behavior. Both relaxation time and AC conductivity diminished with higher dopant concentrations (from 0.000222 Ωm−1 to 0.000036 Ωm−1). The relaxation observed in conductivity and dielectric responses implies their contribution to the charge transport processes within BaCoxAlxFe12-2xO19. Electrochemical impedance spectroscopy (EIS) software was used to generate complex impedance plots, which aligned with the experimentally obtained impedance values for the synthesized compositions. Micrographs revealed a distribution of grains and grain boundaries that were consistent with calculated characteristics. This further substantiates the measured dielectric and electrical parameters.

Optically Active Oxygen Defects in Titanium Dioxide Doped with Inorganic Acid Ions.

Doping inorganic acid ions represents a promising pathway to improving the photocatalytic activity of TiO2, and oxygen vacancy has been regarded as the determinant factor for photocatalytic activity. A series of samples doped with Cl-, NO3-, and SO42- was prepared via a simple sol-gel method. Two different oxygen vacancies in the crystal layer of NO3-/TiO2 and Cl-/TiO2 were found, and those are [Ti3+]-V0-[Ti3+] and [Ti3+]-Cl, respectively. The photocurrent of NO3-/TiO2 with [Ti3+]-V0-[Ti3+] is significantly greater than that of Cl-/TiO2 with [Ti3+]-Cl. The least oxygen vacancy is in the gel layer of SO42-/TiO2, and the negligible photocurrent is due to difficulty in forming a stable sol. Furthermore, the process conditions for the application of TiO2 were investigated in this work. The optimal process parameters are to adjust the solution to pH = 3 during sol-gel preparation, to adopt 550 °C as the calcination temperature, and to use an alkaline electrolyte, while the rest of the preparation conditions remain unchanged. This work reveals a new avenue for designing efficient photocatalysts for air pollutant degradation.

Obtained large room-temperature TCR of La0.67Ca0.25Sr0.08MnO3 ceramics by optimizing sintering temperature

Over the past few decades, perovskite manganese oxide Lax(CaSr)1-xMnO3 has presented new opportunities for uncooled infrared bolometers due to its exceptional electrical transport performance. In this study, La0.67Ca0.25Sr0.08MnO3 (LCSMO) ceramics were prepared at different sintering temperatures (Ts, Ts = 1450, 1470, 1490, 1510, 1530 °C) by changing the previous sol-gel preparation process parameters. The research results indicated that the tolerance factor (τ) of the ceramics is τ = 0.935, and all ceramics exhibit a Pnma space group perovskite structure with excellent crystallinity. LCSMO ceramics exhibit good crystal quality and higher room-temperature TCR (14.58 % K−1) at Ts = 1510 °C. As Ts increases, the grain size, Mn–O bond length (dMn-O), Mn–O–Mn bond angle (θMn-O-Mn) and cell volume (V) of ceramics have a slight affected. The decrease of grain boundary scattering, electron-electron scattering, and strong coupling between electrons, so the peak resistivity value of all sintered samples firstly decreases and then increases with the increase in Ts, which effectively yields ceramics with high TCR. The peak TCR value (TCRmax) increased from 8.38 % K−1 (Ts = 1450 °C) at 296.91 K to 14.58 % K−1 (Ts = 1510 °C) at 298.18 K. On the same component, the TCRmax was increased by 42 % from 8.38 % K−1 to 14.58 % K−1 at Ts = 1450 °C–1510 °C. The high room-temperature TCR of LCSMO is expected to be used in advanced uncooled infrared bolometers, providing a basis for studying the influence of Ts on the electrical transport performance of ceramics.

Trivalent Gd incorporated Zn2SiO4 phosphor material for EPR and luminescence investigations

Abstract Zn2SiO4:Gd3+ powder was obtained by the sol–gel preparation technique and then characterized by using Fourier-transform infrared spectroscopy and X-ray diffraction techniques. The sample exhibited photoluminescence in the ultraviolet spectral zone with a maximum emission wavelength of 314 nm. Ultraviolet emission in the range of 305–320 nm is also called ultraviolet-B emission. This UV range emission is used in lamps for skin treatment and phototherapy. The electron paramagnetic resonance spectrum recorded for the Zn2SiO4:0.015Gd3+ phosphor revealed g values of 3.46, 2.64, and 2.20, confirming the presence of Gd3+ ions in the small ligand field. Furthermore, Gd3+ ions attain tetrahedral symmetry in the prepared host compound.

Modifier-free sol–gel preparation of cotton fiber@SiO2 superhydrophobic fabric for oil/water separation

The oil/water separation material is beneficial to the respective detection of organic and inorganic impurities in samples by retaining the water-soluble impurities in water and the liposoluble impurities in the oil phase. Cotton fiber@SiO2 superhydrophobic fabric was prepared by a facile modifier-free sol–gel method for oil/water separation. By adjusting the hydrolysis and condensation of TEOS, the preparation of superhydrophobic and superhydrophilic fabrics can be achieved. The hydrolysis and condensation of TEOS are simply controlled by changing the content of ammonia water (as a catalyst). When the content of ammonia water is 3–6 %, cotton fiber@SiO2 superhydrophobic fabric was obtained with the water and oil contact angle of ∼ 156° and 0°, respectively. When the content of ammonia water is 7–10 %, cotton fiber@SiO2 superhydrophilic fabric was realized. In addition, the as-prepared cotton fiber@SiO2 superhydrophobic fabric can be used for the separation of oil/water mixtures with a separation efficiency of 98 %. Finally, the mechanism for the modifier-free sol–gel preparation of cotton fiber@SiO2 superhydrophobic and superhydrophilic fabric was discussed.

Assessment of superconducting and structural stability of advanced Y-123 and Y-358 ceramics with Tb/Y substitution in main matrices

In this study, the performances of Y1-x(Tb)xBa2Cu3O7-δ (Y-123) and Y3-x(Tb)xBa5Cu8O18-δ (Y-358) advanced ceramics prepared by sol-gel preparation route are investigated by the advanced characterization methods including X-ray diffraction (XRD), temperature dependent resistivity (ρ-T), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and energy distribution spectroscopy (EDS) measurements and theoretical approaches. The EDS results illustrated that the Tb impurities were replaced successfully by the yttrium sites in the YBa2Cu3O7-y main matrix. Similarly, it was noted that the presence of excess impurities in the crystal structure led to the oxygenation problems. Electrical properties were determined by temperature dependent resistivity (ρ-T) measurements. ρ-T results indicated that Tb doping reduced the critical transition temperature (Tc) values for the transition to superconductivity for all samples in two YBCO phases. Although it appears to have negative effects of Tb ions on the number of mobile charge carrier concentrations in the σ antibonding in-plane Cu-O bonds, bipolaron formations in the polarizable lattices, oxidation states, and amplitude of the pair wave function of both phases, the other valuable properties (morphology, crystallinity quality, interaction between adjacent layers, critical current density, and flux pinning ability) were noted to improve remarkably in the case of the optimum amount in the Y-123 superconducting phase. In this context, the Y-358 superconducting phase was harshly affected by the substitution due to the change of the ortorombicity, localization problem, impurity phases, structure stabilization, crystal structure quality, crystallization system, homogeneities of oxidation states, oxygen ordering degree, and impurity scatterings. Besides, the analysis of the fluctuation induced conductivity indicated that the Y-123 ceramics with longer c-axis coherence length and less anisotropic nature exhibited well superconducting properties. Additionally, the doping ratio of x=0.01 led to the formation and distribution of more nucleation centers for the thermal fluxon motions of 2D pancake vortices. Similarly, the optimum Tb doped Y-123 system exhibited much durable to applied field strengths due to the best interaction quality between grains. Accordingly, this study recommended that the Y1-x(Tb)xBa2Cu3O7-δ advanced ceramic structure with new functionalities can find much more application areas in innovative, heavy-industrial technologies, and advanced engineering-related sectors.

Dosimetric properties of Cr–La, Cr–Cu, and Cu–La ions codoped Ca9 Al (PO4)7 nanostructure

In the present work, Cr–La, Cr–Cu, and Cu–La ions codoped Ca9Al (PO4)7 nanostructures (symbolized as Cr–La, Cr–Cu, and Cu–La) were prepared using the sol-gel method for their dosimetric properties. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results reflected the existence of the nanoparticle structure. This confirmed the successful sol-gel preparation method used. The surface morphological properties of the prepared samples were scrutinized by scanning electron microscopy (SEM). The presence and distribution of the constituent elements of the samples were determined using energy-dispersive X-ray (EDX) spectroscopy. The thermoluminescence (TL) sensitivity enhancement and homogenous properties of the prepared samples were assessed using a γ-radiation dose of 5 Gy. TL sensitivity of the Cr–Cu sample was found to be optimum. The relative standard deviations (RSD) of the homogenous study were found to be 6.5, 5.7, and 3.9% for Cr–La, Cr–Cu, and Cu–La, respectively, which were acceptable according to the ISO requirements (<10%). The dose-linearity response was investigated in 0.5 up to 20 Gy γ-dose ranges. The sample Cr–Cu had a good dose-linearity of up to 20 Gy while the others (Cr–La and Cu–La samples) had a dose-linearity of up to 13 Gy. The threshold doses (MDD) of the Cr–La, Cr–Cu, and Cu–La samples were computed and found to be approximately 110, 32, and 134 μGy, respectively. The photon attenuation parameters of the prepared samples were computed using the Phy-X PSD program, and the acquired data showed that the Ca9Al (PO4)7 composition had bone-equivalent material characteristics. Results of the dosimetric properties of Cr–La, Cr–Cu, and Cu–La co-doped Ca9Al (PO4)7 samples suggested that these compositions had potentially excellent TL characteristics to be used in various dosimetric applications across a broad range of gamma doses.

Combustion-mediated sol–gel preparation of cobalt-doped ZnO nanohybrids for the degradation of acid red and antibacterial performance

Abstract The present study explores the combustion-mediated sol–gel preparation of the cobalt-doped ZnO (Co/ZnO) nanohybrids. The characterization results of as-prepared samples were investigated using analytical instruments like FTIR, XRD, XPS, SEM, UV-Vis DRS, BET, and TGA. The doping of cobalt into ZnO was achieved at a lower particle size (21.3 nm) than the pure ZnO (29.6 nm). We observed that the Co-doped ZnO grain size seems to be in abundance and diversity than that of the undoped ZnO. Further examination was carried out with photocatalytic degradation of acid red (AR) dye under visible light illumination and antibacterial performance over Spingomonous pausimobilis and Streptococcus pyrogenes to assess the catalytic performance of the prepared Co/ZnO nanohybrid. The photocatalytic degradation results from the optimum reaction conditions are 150 mg of catalyst loading, pH 2, and 10 ppm of initial AR dye concentration, and the complete degradation of AR dye in 120 min. The antibacterial performance of the Co/ZnO nanohybrid was measured and was found to be 25 and 16 mm for S. pausimobilis and S. pyrogenes, respectively, with respect to the control chloramphenicol.

Flexible, Thermally Stable, and Ultralightweight Polyimide-CNT Aerogel Composite Films for Energy Storage Applications.

Polyimide (PI) aerogels are promising in various fields of application, ranging from thermal insulators to aerospace. However, they are typically in the form of a bulk monolith, which suffers from a lack of conformability and drapability. Moreover, their electrical conductivity is limited, and they mainly display an insulative behavior. These shortcomings can limit the applications of PI aerogels in energy storage systems, which require ultralightweight flexible conductive films, which at the same time offer high thermal stability, ultralow density, and high surface area. To overcome these obstacles, the present study reports the fabrication of PI-carbon nanotube (PI-CNT) aerogel composite films with varying CNT content prepared through a sol-gel preparation method, followed by a supercritical drying procedure. Compared to pristine PI aerogels, which displayed a large shrinkage and density of 18.3% and 0.12 g cm-3, respectively, the incorporation of only 5 wt % CNTs resulted in a significant reduction of both shrinkage and density to only 11.5% and 0.10 g cm-3, respectively. This suggests the importance of CNTs in improving the dimensional stability of aerogels and creating a robust network. Further characterizations showed that incorporation of 5 wt % CNTs also resulted in the highest pore volume (1.25 cm3 g-1), highest surface area (324 m2 g-1), highest real permittivity (80), highest electrical conductivity (3 × 10-1 S m-1), and ultrahigh service temperature (575 °C). It was also shown that the aerogel films can withstand a large degree of bending, can be twisted, and can be fully rolled with no obvious cracks propagated in the structure. The combined outstanding properties of the developed aerogel composite films make them promising potential candidates for supercapacitor electrodes. Therefore, the electrochemical performance of the devices based on aerogel electrodes was further studied. The device demonstrated a high energy density of 2.6 Wh kg-1 at a power density of 303.8 W kg-1. The total capacitance after 5000 cycles was 91.8% of the initial capacitance, which indicated excellent stability and durability of the device. Overall, this work provides a facile yet effective methodology for the development of high-performance aerogel materials for energy storage applications.

Synthesis and characterization of TiO2-carbon filter materials for water decontamination by adsorption-degradation processes

Wastewater treatment is becoming ever more challenging due to the increasing levels of molecular pollutants that are challenging for existing approaches. Innovative materials are required to help produce potable water from heavily contaminated water sources. One such material is titanium dioxide-activated carbon (TiO2/AC) heterostructures, which combine the photocatalytic properties of TiO2 with the adsorption properties of the ACs. To date, studies on TiO2/AC heterostructures for real-world water purification have yet to be performed. This study aimed to address this gap by comparing the effectiveness of titanium isopropoxide (Ti(OiPr)4) and titanium butoxide (Ti(OBu)4) for synthesizing TiO2/AC heterostructures using four different methods (sol-gel, solvothermal, and microwave-assisted hydrothermal methods [x2]). The elaborated heterostructures were compared with commercial TiO2 materials for their ability to degrade five emerging contaminants (caffeine, hydrochlorothiazide, saccharin, sulfamethoxazole, and sucralose). Hydrochlorothiazide and sulfamethoxazole were demonstrated to be rapidly degraded by UV-C irradiation within 15 min. Caffeine, saccharin, and sucralose were less susceptible to UV degradation. All the elaborated TiO2/AC heterostructures consisted of pure anatase phase, with Ti(OBu)4 syntheses generating larger average crystal sizes and lower surface areas. Sol-gel preparations produced the most effective TiO2/AC heterostructures due to their high surface area. Compared with the commercial TiO2, the heterostructures enhanced the photocatalytic activity of TiO2 by up to 10.0 times. Also, the heterostructures remained effective at environmentally relevant conditions (i.e., concentration of the contaminant and water matrices). The reuse of the materials was tested and showed no reduction in efficiency after four removal/regeneration cycles. Overall, this study presents novel TiO2/AC heterostructures with increased photocatalytic efficiency that can serve as an efficient material for removing contaminants at large scales (e.g., water treatment plants).

Silica Gels Doped with Gold Nanoparticles: Preparation, Structure and Optical Properties.

A novel, one-pot sol-gel preparation scheme leading to reproducible incorporation of 20-40 nm sized gold nanoparticles (AuNPs) in SiO2 gels is developed based on in situ reduction during gelation using chloroauric acid and ascorbic acid. Variation in the preparation conditions affects the chemical composition, optical properties and size distribution of the AuNPs incorporated in the silica gels. Different organic dopants, i.e., oleic acid, acetic acid or dodecanethiol, are applied to modify the final composite material and to control the rate of reduction and growth of the AuNPs in the gels. The synthesized samples are characterized by UV/Vis/NIR spectroscopy, X-ray diffraction, transmission electron microscopy, thermal conductivity measurements and DTA/TG measurements. The optical properties of the obtained composites are explained using Mie theory. The incorporation of AuNPs leads to an increase in the thermal conductivity of the silica gels. The best process method in this contribution is the use of NaOH as a gelation catalyst and oleic acid as an organic modifier, leading to 20 nm AuNPs dispersed in the silica matrix.

CO2 methanation with high-loading mesoporous Ni/SiO2 catalysts: Toward high specific activity and new mechanistic insights

In the power-to-gas scenario, surplus renewable electricity is stored in the form of methane, by reacting green hydrogen with waste CO2 through the Sabatier reaction. Low-cost catalysts that feature a high activity at low temperature are needed. We disclose the sol–gel preparation of high-loading mesoporous Ni/SiO2 catalysts. (HR)-TEM, XRD, N2 physisorption, and H2 chemisorption show that small Ni particles (<5 nm) are obtained, even at loading up to 38 wt%. The best catalyst reached a specific activity of 10.2 µmolCH4.g−1.s−1 at 250 °C (TOF = 0.0155 s−1; almost 3 times higher than a reference catalyst prepared by impregnation). Being based on inert silica, these catalysts are ideal model materials to elucidate the reaction mechanism on nickel. Combining CO2-TPD, in-situ CO2-DRIFTS, and TPSR with DFT calculations, we show that CO2 methanation follows mostly the RWGS + CO-hydrogenation and the formate pathways, the former being dominant at low temperature.

Sol-gel method preparation and high-rate energy storage of high-entropy ceramic (FeCoCrMnNi)C porous powder

Among the existing electrochemical capacitive energy storage electrode materials, the (TiNbTaZrHf)C, (VCrNbMoZr)2N, (CoCrFeMnNi)3O4, (FeCoCrMnMg)3O4 and (FeCoCrMnCuZn)3O4 all have excellent capacitive performance, but the energy density is limited due to the narrow potential window. In order to solve the problem of low energy density of electrochemical supercapacitor, a kind of high-entropy carbides (HEMCs) with broad potential window is designed from generalized analysis of electrochemical window of active elements. This high-entropy carbide contains five active elements of Fe, Co, Cr, Mn and Ni. The prepared HEMC-3 has abundant pores and a specific surface area of 417.8 m2 g−1. The large specific surface area makes the HEMCs have high-rate energy storage performance. Electrochemical tests show that the HEMC-3 presents a potential window of [-1.0, 0.6] versus Hg/HgO, and can obtain a specific capacitance of 169.7 F g−1 at a current density of 0.5 A g−1. Due to the designed wide potential window of the prepared HEMCs, the energy density has been greatly improved, which shows a new strategy for developing of electrochemical supercapacitor electrode materials.

Sol-Gel preparation and wetting behaviour analysis of hydrophobic Zirconium based nano-coating: Implications for solar panel coating

Hydrophobic coatings basically decrease the wettability of surface due to the presence of nanostructures on it. In this research work, nanozirconia sol was prepared by the sol-gel method and further hydrophobically modified using the hexamethyldisilazane (HMDS). Prepared sol was coated on the glass substrate and then analysed for its wetting behaviour. Three samples with different HMDS ratios mixed to Zirconia sol were coated, and analysed for surface morphological parameters through the atomic force microscopy and field emission scanning electron microscopy techniques. The wetting behaviour was analysed by studying the water contact angle and surface free energy of the samples. Here the transmittance was measured by transmittance metre at regular intervals for 30 days. Functional group determination was done by Fourier transform infrared spectrometer that confirmed the formation of Zirconium nanoparticles. Maximum contact angle of 101.2° was observed that showcased the hydrophobic properties. Hydrophobic coating was then successfully prepared, and sample with 2:1 ratio of Zirconium nanoparticles and HMDS showed the best hydrophobic nature amongst all the coatings prepared in this investigation.