Nitrogen Adsorption-desorption Measurements Research Articles

Influence of Rapid Heat Treatment on the Photocatalytic Activity and Stability of Barium Titanates Against a Broad Range of Pollutants.

Barium titanate photocatalysts were synthesized via a sol-gel method involving a unique, cost-effective calcination technique that includes rapid heating and short exposure. The samples were characterized by X-ray diffractometry, scanning electron microscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, infrared spectroscopy, and nitrogen adsorption-desorption measurements. The photooxidation activity and stability of the samples were evaluated by the degradation of phenol, oxalic acid, and chlorophenol. Their photoreduction activity was also investigated by the photocatalytic conversion of CO2 to CO. In both cases, UV irradiation was applied to activate the catalysts. As references, commercially available cubic and tetragonal barium titanates were used, with the addition of benchmark P25 TiO2 in some cases. Increasing the calcination temperature resulted in increased primary crystallite sizes, decreased specific surface areas, and slightly redshifted band gaps. On the one hand, the overall photooxidation activity of the samples for pollutant degradation was rather low, possibly due to their unfavorable valence band maximum position. On the other hand, our samples displayed significantly superior photoreduction activity, surpassing that of all the references, including P25 TiO2. The high photoactivity was mainly attributed to the specific surface areas that changed per the efficiency of the samples. Last, the cost comparison calculations showed that applying our calcination technique is 29.5% more cost-efficient than conventional calcination, and the same amount of energy is sufficient for preparing even a 1.4 times higher amount of barium titanite.

Impact of early-age vibration on the permeability and microstructure of mature-age concrete

Dynamic excitation in early-age significantly impacts the performances of mature concrete in underground structures, such as tunnels beneath railways supported by cast-in-place concrete. This study explores the impact of early dynamic excitation on properties of mature concrete. Vibration tests at a fundamental frequency of 114 Hz, with peak acceleration levels ranging from 0.1 g to 0.4 g, were conducted using shaking table. Specimens underwent 33 seconds of dynamic excitation every 15 minutes over the initial 48 hours, excluding a night break from 0 to 6am, totaling 114 vibration cycles. Various lab tests were employed to assess the properties and microstructure of mature concrete post-vibration, including water penetration resistance, capillary water absorption, Coulomb electric flux, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and Nitrogen adsorption-desorption measurement (NAM). The results proves that vibration causes water secretion and air bubbles discharge before the initial setting of concrete, thereby enhancing the hydration reaction. The relationship between vibration loads with varying peak accelerations and the cohesion resulting from hydration reaction influences the microstructural evolution of concrete, leading to the weakening and strengthening of permeability of mature concrete. Under the vibration spectrum and test conditions described in this paper, vibration loads with peak values less than 0.234 g decrease the total volume of large and middle pores (>20 nm) by up to 50 % and increase the total volume of small pores (<20 nm) by up to 200 %. Due to these changes in pore structure, the permeability coefficient (Sk), cumulative capillary water height (i) and Coulomb electric flux decrease by up to 47.84 %, 39.5 % and 31.6 %, respectively. However, when the amplitudes of vibration loads exceed 0.234 g, the total volume of large and medium pores (>20 nm) increases, and that of small pores (<20 nm) decreases, leading to a reduction of the impermeability of mature concrete. Additionally, the SEM analysis corroborates these microstructural variations.

Boosting Suzuki coupling reaction via pore expanding and palladium–zinc alloying

A palladium–zinc alloy nanoparticles decorated nitrogen-doped porous carbon catalyst (PdZn30–NC) was synthesized and utilized for Suzuki coupling reaction. The alloying palladium (Pd) with zinc (Zn) and pore expanding are realized simultaneously. Density functional theory (DFT) calculations and experimental studies reveal that the alloying Pd with Zn can lower the energy barrier in Suzuki coupling reaction. Nitrogen adsorption–desorption measurements uncover that pore expansion caused by the zinc nitrate hexahydrate assisted calcination gives rise to the multiplication of mesopore with a pore diameter of 6 nm, which facilitates mass transfer during the reaction. As a result, the alloying Pd with Zn and pore expanding together endow PdZn30–NC with excellent catalytic activity. PdZn30–NC demonstrates exceptional catalytic activity and stability in Suzuki coupling reaction. A high biphenyl yield of 97.7 % within 40 min and stable reusability of 93.3 % yield after five reuse cycles can be achieved. This work not only offers a viable method for Suzuki coupling reaction, but also provides insights for designing new catalysts toward Suzuki coupling reaction.

Effect of Ce-doping on the structural, morphological, and electrochemical features of Co3O4 nanoparticles synthesized by solution combustion method for battery-type supercapacitors

This study investigates the potential of cerium (Ce) doping to improve the performance of cobalt oxide (Co₃O₄) nanoparticles as battery-type supercapacitor electrodes. Pure Co₃O₄ nanoparticles were synthesized via a solution combustion method and then doped with 2.5 % (Ce-Co3O4) and 5 % Ce (CeO2-Co3O4). Comprehensive characterization, including X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM), was used to analyze the impact of Ce doping on the material properties. XRD analysis confirmed the successful incorporation of Ce into the Co₃O₄ structure, with distinct CeO2 phases forming at higher doping levels. Ce doping resulted in decreased crystallite size and peak intensity, indicating reduced crystallinity and increased defect concentration. Raman spectroscopy corroborated these findings, showing a redshift that suggests weakened metal-oxygen bonds and smaller grain sizes due to Ce³⁺ incorporation. FESEM images demonstrated that Ce doping effectively reduced nanoparticle agglomeration, with 2.5 % doping leading to smaller particles and 5 % doping promoting a 2D flake-like morphology with increased porosity. Nitrogen adsorption-desorption measurements revealed a significant increase in surface area and pore volume for CeO2-Co₃O₄, facilitating improved electrolyte diffusion and reduced resistance, thereby enhancing electrochemical performance. Evaluation of the electrochemical properties of undoped and Ce-doped Co₃O₄ materials revealed a battery-like response in a three-electrode configuration. Notably, the CeO2-Co3O4 exhibited a superior specific capacity of 603.3 C g−1 at a current density of 1 A g−1, significantly exceeding the values of 368.5 C g−1 and 127.1 C g−1 achieved by Ce-Co3O4 and undoped Co3O4, respectively. Furthermore, the CeO2-doped Co3O4 demonstrated exceptional cyclic stability, retaining 87 % of its initial capacity after undergoing 5000 charge-discharge cycles at a high current density of 10 A g−1. These results suggest that Ce doping is a promising strategy for optimizing Co₃O₄-based battery-type electrode materials, potentially leading to the development of high-performance and cost-effective energy storage systems.

Assessment of the physiochemical properties and sustainability of locally produced ceramic G-filter in a long term experiment

In India, Ceramic Water Filters (CWF) named G-filters are becoming a point-of-use household water treatment solution. The filter's reliability may be primarily characterized by the filtrate turbidity and microbial removal efficiency. The temperature and moisture gradients of the location affect its performance. This paper describes a 19-week laboratory investigation of G-filters simulating field conditions. The basic objective during the study was to ascertain the effective useable life of the filter. The discharge rate and turbidity reduction ability of the filters are studied in depth. The G-filters were prepared using locally available salty clay and sawdust taken in equal volume fractions. A total of 30 filters with a 9-liter capacity each were used for the experiments. The results showed that CWFs can reduce turbidity effectively. The influent water used for the study had a mean turbidity of 7.65 NTU, which reduced in the range of 0.03 NTU to 1.03 NTU. Over the course of four months, the average flow rate decreased from 1.94 Lh-1 to 0.93 Lh-1. Although a soft brushing of filters improved the filtration rate but that too failed in the long run. Brunauer–Emmett–Teller (BET) nitrogen adsorption–desorption measurements were used to determine the variation in pore size of filters with time. An average pore radius of 2.91 nm was found in the original filter that has not been used for filtration experiments. Moreover, an average pore radius of 1.77 nm, 1.21 nm, and 1.22 nm were reported in G-filters through which 427.5 L, 807.5 L, and 1035.5 L, respectively, of water were passed. This reduction in pore size is attributed to the clogging of pores over a period of time. This study aims to collect performance data to establish a scientific model using statistical analysis for implementing CWF technology in developing nations.

Preparation of bulk micro–mesoporous silica-supported ZnO via silicic acid as a desulfurizer

Silicic acid solution, which is prepared from water glass followed by extraction with tetrahydrofuran (THF), is focused on an environmentally friendly and inexpensive source of silica. In this study, we aimed the preparation of bulk porous silica with low environmental impact and cost, and desulfurization of its supported ZnO was investigated. Bulk porous silica was prepared by the condensation of silicic acid/THF in the presence of Pluronic P123. Suitable condition was investigated for the formation of crack-free bulk body with high surface area and reproducibility under the molar ratio of H2O/Si and Si/Pluronic P123 on 121 and 100, respectively. From nitrogen adsorption–desorption measurements, this bulk porous silica was categorized into micro–mesoporous silica. Moreover, Pluronic P123 was extracted and recycled. Bulk porous silica-supported 15 wt% ZnO was prepared by the impregnation of ZnCl2 followed by calcination in air. The desulfurization ability was 8.7 mg/g.Graphical

One-Pot Preparation of Mixed-Mode Reversed-Phase Anion-Exchange Silica Sorbent and its Application in the Detection of Cyclopiazonic Acid in Feeds and Agricultural Products.

A novel co-bonded octyl and pyridine silica (OPS) sorbent was prepared and applied for the solid phase extraction (SPE) of cyclopiazonic acid (CPA, a type of mycotoxin) in feed and agricultural products for the first time. A simple mixed-ligand one-pot reaction strategy was employed for OPS sorbent preparation. Nitrogen adsorption-desorption measurements, elemental analysis (EI), thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR) analysis demonstrated the successful immobilization of octyl and quaternary ammonium groups onto the surface of silica gel. The large specific surface area, high-density functional groups, and mixed-mode anion-exchange characteristics of these silica particles made them the ideal material for the efficient extraction of CPA. Additionally, the OPS sorbents displayed excellent batch-to-batch reproducibility, satisfactory reusability, and low cost. The SPE parameters were optimized to explore the ionic and hydrophobic interactions between CPA and the functional groups, and the ultra-high performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UPLC-MS/MS) parameters were optimized to obtain a desirable extraction efficiency and high sensitivity to CPA. Meanwhile, the OPS sorbent presented a satisfactory extraction selectivity and low matrix effect. Under the optimized conditions, our developed CPA detection method was used to determine CPA level in rice, wheat flour, corn flour, peanut, and feed samples, exhibiting a lower detection limit, better linearity, higher sensitivity, and satisfactory extraction recovery rate than previously reported methods. Therefore, our method can be preferentially used as a method for the detection of CPA in agricultural products and feeds.

Studies on the Process of Basic Dyes Adsorption on Uniform Spherical Carbons.

The influence of carbon pore structure on the sorption process of selected cationic dyes has been investigated. The structure and surface of carbonaceous materials have been characterized basing on various techniques: scanning electron microscopy, low temperature nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy and thermal analysis combined with identification of gaseous products. The kinetic and equilibrium adsorption measurements of Basic Violet 3, Basic Red 1 and Basic Blue 9 from aqueous media were performed. The studied carbons seem to be promising adsorbents towards dyes, taking into account the easy-to-use uniform spherical form of the granules and a complex type of porosity with micro-, meso- and macropores appropriate for large molecule adsorption.

Ionic Liquid Modified Polymer Gel for Arsenic Speciation.

A new ionic liquid modified polymer gel containing methylimidazolium groups (poly(MIA)) is proposed as a sorbent for the separation and enrichment of trace inorganic and organic arsenic species in surface waters. The poly(MIA) was synthesized by chemical modification of polymeric precursor using post-polymerization modification of poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate). The composition, structure, morphology, and surface properties of the prepared particles were characterized using elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption measurements. Optimization experiments showed that at pH 8, monomethylarsonic acid (MMAs), dimethylarsinic acid (DMAs), and As(V) were completely retained on the poly(MIA), while the sorption of As(III) was insignificant. The desorption experiments revealed that due to the weaker binding of organic arsenic species, selective elution with 1 mol/L acetic acid for MMAs + DMAs, followed by elution with 2 mol/L hydrochloric acid for As(V), ensured their quantitative separation. The adsorption kinetic and mechanism were defined. The analytical procedure for As(III), As(V), MMAs, and DMAs determination in surface waters was developed and validated through the analysis of certified reference material.

Feroxyhyte - from synthesis and characterization to application.

Feroxyhyte (δ-FeOOH) was synthesized and characterized using X-ray diffractometry (XRD), simultaneous thermal analysis (STA), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), and low-temperature nitrogen adsorption-desorption measurements. Its potential application as adsorbent of an anionic and cationic dyes such as C.I. Acid Violet 1 (AV1) and C.I. Basic Blue 3 (BB3) was investigated by determining the adsorption capacities based on the Langmuir (36.6 mg/g for AV1 and 187 mg/g for BB3), Freundlich and Dubinin-Radushkevich isotherm models. Adsorption of AV1 and BB3 by δ-FeOOH drops with the presence of additives such as cationic and anionic surfactants (CTAB, SDS) and ionic polymers (PAA, PEI). The surface and electrokinetic properties of examined suspensions were also described. They include determination of the solid surface charge density and the zeta potential, as well as values of point of zero charge and isoelectric point of feroxyhyte particles without and with adsorbed layers of organic substances. Their analysis made possible to propose the most probable structure of electrical double layer formed at the iron mineral/aqueous solution interface.

Dendritic bifunctional nanotraps inside SBA‐15 for highly efficient removal of selected nonsteroidal anti‐inflammatory drugs from wastewater

AbstractLarge‐pore mesoporous SBA‐15 materials were functionalized with dendritic bifunctional ligands to achieve efficient adsorption of nonsteroidal anti‐inflammatory drugs (NSAIDs) in aqueous solution mainly through a combination of anion‐exchange ability of quaternary ammonium cations and π‐π interaction capability of oxygen activated phenyls. The synthesis of such a dendritic ligand starts from propylamine on SBA‐15 followed by consecutive amine‐epoxy reactions with resorcinol diglycidyl ether (RDGE) and methylamine, and then amination of terminal epoxy with trimethylamine. The results from Fourier‐transform infrared spectroscopy, nitrogen adsorption–desorption measurements and elemental analysis reveal that the bifunctional dendritic nanotraps have been created successfully inside the mesochannels of SBA‐15 (DNT@SBA‐15). Adsorption kinetics for NSAIDs was very rapid following a pseudo‐second‐order kinetic model, and adsorption isotherms were fitted well by the Langmuir isotherm model. Notably, DNT@SBA‐15 demonstrated remarkably high adsorption capacities for NSAIDs, with maximum values of 1037.3 mg g−1 for ibuprofen, 821.3 mg g−1 for naproxen and 781.3 mg g−1 for diclofenac at pH 7.0. The adsorption was presumed to be governed by a dual‐interaction mechanism including electrostatic and van der Waal's interactions. This study demonstrates that the developed dendritic anion‐exchanger can be a promising material for removing NSAIDs adsorption from environmental water.

Highly stable hybrid porous polymers containing polyhedral oligomeric silsesquioxane (POSS)/Dibenzo[g,p]chrysene and Dibenzo[b,d]thiophene units for efficient Rhodamine B dye removal

In this study, we employed the Heck reaction method to synthesize three types of hybrid porous organic/inorganic polymers (HPPs) incorporating octavinylsilsesquioxane (OVS) units. Specifically, we synthesized OVS-TBN-DBTH, OVS-TBN-THS, and OVS-TBN-THSO2 HPPs by reacting OVS with different brominated organic compounds, namely, 2,7,10,15-tetrabromodibenzo[g,p]chrysene (TBN-Br4)/2,8-dibromodibenzo[b,d]thiophene (DBTH-Br2), TBN-Br4/2,3,7,8-tetrabromothianthrene (THS-Br4), and TBN-Br4/2,3,7,8-tetrabromothianthrene-5,5,10,10-tetraoxide (THSO2-Br4). Based on thermal analysis (TGA), the onset decomposition temperatures (Td10) for these HPPs were as follows: OVS-TBN-DBTH at 575 °C, OVS-TBN-THS at 313 °C, and OVS-TBN-THSO2 at 490 °C. Additionally, these HPPs exhibited high char yields, with values of 83, 53, and 67 wt% for OVS-TBN-DBTH, OVS-TBN-THS, and OVS-TBN-THSO2 HPPs, respectively. Furthermore, when analyzed using nitrogen adsorption–desorption measurements, both OVS-TBN-DBTH and OVS-TBN-THSO2 HPPs demonstrated impressive specific surface areas (SBET) of up to 380 m2/g. In addition, the OVS-TBN-DBTH and OVS-TBN-THSO2 HPPs provide an adsorption capacity of 70.62 and 77.1 mg g−1 (qmax from Langmuir isothermal Mode) toward RhB dyestuff at room temperature. In this adsorption system, after calculation, the OVS-TBN-THS HPP could be inferred that the adsorption is a pseudo-first order adsorption model. The OVS-TBN-THS HPP and OVS-TBN-THSO2 HPP in the pseudo-secondary order model have a better representation of the adsorption system for rhodamine B. This study introduces an innovative method for developing HPPs as adsorbents for water treatment and purification.

Toward clima-resilient ultra-high performance concrete (UHPC): A survey on high-strength mortars engineered with extra-low dosage graphene-based materials (GBMs)

Latest advances showed that ultra-high performance concrete (UHPC) holds the potential to meet the criteria of future civil infrastructures. Several nanofillers (NFs) proved to enhance the performance of UHPC in terms of economic and environmental sustainability and even assigning novel features. Presently, this promising approach is still in its early stage. In this perspective, mortars based on Portland cement CEM I 52.5 N were engineered with extra-low dosage (0.01% by weight of cement) graphene nanoplatelets (GNPs) or nanographite (nG). An acrylic superplasticizer for high-strength concrete was used as additive. Fresh properties of the cementitious admixtures were characterized by viscosity measurements, flow table and bleeding tests. Prismatic specimens were hardened in water at room temperature for 28 days. Microstructure was observed by Scanning Electron Microscopy, the pore structure and specific surface area (SSA) investigated by Mercury Intrusion Porosimetry (MIP) and nitrogen adsorption-desorption measurements, thermal behavior studied by thermogravimetry, and mechanical strength evaluated by compression and bending tests. Electrical resistivity was determined by Electrochemical Impedance Spectroscopy (EIS). Both 2D-NFs induced a slight lubricant effect that did not significantly affect neither workability nor bleeding. GNPs do not appreciably impact on the mechanical properties of the hardened nano-engineered materials, a decay of bending strength was observed only for nG-loaded samples. The positive impact of the extra-low dosage GNPs on the hardened mortars was clearly detected by MIP and EIS in terms of reduced porosity (−31%), improved bulk density (+5.7%), pore refining (median and average pore diameter −35% and −9%, respectively), increased resistivity (+97%) and lowered predicted intrinsic permeability (−52%). In the same experimental condition, nG-engineered mortars suffered from uneven dispersion that led to increased porosity and pore coarsening.

Influence of thermal and acidic treatments on the morphology of a natural kaolinitic clay mineral

In this work, a natural kaolinitic clay mineral from Kribi in Cameroon is modified by thermal and acidic treatments. The influence of these treatments on the physicochemical properties of the clays is studied using X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption measurements, scanning electron microscopy, inductively coupled plasma–atomic emission spectroscopy and thermal analysis. Three calcination temperatures are explored: 600, 700 and 800 °C. The XRD pattern of the untreated clay showed that the natural clay mineral was mostly composed of kaolinite. Calcination at high temperatures allowed the amorphization of the natural kaolinitic clay mineral to obtain metakaolinite. This heat treatment of the natural clay mineral produced disintegration by rupture of the strong hydrogen bonds between the layers of the clay mineral. Heat treatment did not increase the specific surface area of the clay, which stayed around 20-30 m2/g. The acid treatment produced a high material texture modification giving microporous materials with a large surface area up to 315 m2/g with the sample previously calcined at 800 °C. The microporosity and mesoporosity increase is greater when the clay is calcined at high temperature. The morphology of the samples observed by SEM are modified by the acidic treatment. The initial two-dimensional stacking of particles evolves towards a narrower three-dimensional porous structure. These treatments open the way to produce highly porous clay materials that could be used as adsorbent materials for pollutant removal from water.

Effect of nano-silica extracted from two different plant sources on survival and development of Phthorimaea opercullela (Zeller) larvae

Summary The study examined the effect of nano-silica extracted from two different plant sources on the survival and development of the potato tuber moth, Phthorimaea opercullela. The silica powder was derived from two different agricultural byproducts, olive stones and corncobs. Characterization by X-ray diffraction revealed that the extracted powder has an amorphous silica phase. The nitrogen adsorption-desorption measurements revealed that both extracted and treated silica have mesoporous structure, with a specific surface area of around 300 m2/g and 270 m2/g for the silica derived from olive stones and corncobs, respectively. The silica nanoparticles (SiO2 NPs) prepared from the silica derived from olive stοnes showed higher larvae mortality, pupae weight, and larval and pupal developmental time, compared to the silica derived from corncombs. The results show that the nano-silica derived from agriculture byproducts can be as effective as the synthetic insecticide (deltamethrin) utilized in control of the potato tuber moth, with lower environmental impact in terms of preventing pesticide residue accumulation. In addition, the efficiency of SiO2 NPs applications depends on the source of the silica nanoparticles and the applied concentration to achieve the optimum results for the pest control.

Construction of polydopamine-polyethyleneimine composite coating on the surface of poly (styrene–divinylbenzene) microspheres followed by quaternization for preparation of anion exchangers

As a mussel-inspired material, dopamine (DA) is widely applied for the surface modification of various bulk materials based on its self-polymerization properties. Whereas, polydopamine (PDA) modified poly (styrene–divinylbenzene) (PS-DVB) microsphere is still hard to be quaternized under mild conditions. In this work, polyethyleneimine (PEI) is selected as the comonomer to participate in the crosslinking with PDA to form PDA-PEI composite coating on the surface of PS-DVB microsphere. Then, PS-DVB@PDA-PEI microsphere is further quaternized utilizing PDA-PEI coating as the secondary functionalized platform to prepare anion exchanger. The anion exchanger is characterized by scanning electron microscope, fourier transform infrared spectroscopy, nitrogen adsorption–desorption measurement, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis. The chromatographic performance is evaluated by separating seven conventional anions, organic weak acids, et. al. The results indicate that PDA-PEI shows higher reactivity than PDA due to the present of abundant amine groups. The introduce of PDA-PEI coating makes PS-DVB microspheres can be quaternized under mild conditions. The strategy presented here is very suitable for the preparation of anion exchangers.

Catalytic Ozonation of Pesticide Wastewater by Using MCM-41 and ZSM-5/MCM-41 as Catalysts

In the present study, two catalysts, MCM-41 and ZSM-5/MCM-41, were prepared by the hydrothermal synthesis method and their catalytic ozonation performances on pesticide wastewater were investigated. MCM-41 and ZSM-5/MCM-41 were proved to be a mesoporous structure and a micro-mesoporous structure, respectively, by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption measurements. The experimental results indicated that the chemical oxygen demand (COD) removal rate increased from 57.46% without catalysts to 79.35% and 87.56%, respectively, in the presence of MCM-41 and ZSM-5/MCM-41 after 100 min of catalytic ozonation. The catalytic activity of ZSM-5/MCM-41 was found to be greater than that of MCM-41. OH· played an important role in the catalytic ozonation, which was verified by the tert-butanol test. The catalysts had highest activity at pH of 7, and both higher and lower pH values reduced the catalytic ozonation. The optimal ozone dosage was found to be 22.0 mg L−1 min−1 for the COD removal of the pesticide wastewater. The catalysts could be reused five times without significant loss of the catalytic activity, suggesting that the catalysts could be promising catalysts for the catalytic ozonation of the pesticide wastewater.

Hydroformylation of Alkenes over Phosphorous-Free Rhodium Supported on N-Doped Silica

A new phosphorous-free rhodium supported on a nitrogen-doped silica was successfully used as a catalyst for the hydroformylation of alkenes. The obtained material and the catalyst were characterized by XRD, XPS, FTIR, SEM, TEM, ICP AES, and low-temperature nitrogen adsorption–desorption measurements. The catalytic performance was studied by the example of the hydroformylation of octene-1 at temperatures of 80–140 °C and a pressure of 5.0 MPa. The catalyst provided a 99% conversion of 1-octene with a 98% yield of aldehydes and showed a good conversion of styrene and cyclohexene. The catalyst can be repeatedly used in ten consecutive cycles, with its activity remaining constant.

Porous activated carbon materials from Triphala seed stones for high-performance supercapacitor applications

Porous activated carbon materials derived from biomass could be the suitable materials for high-rate performance electrochemical supercapacitors as it exhibits high surface area due to well-defined pore structure. Here, we report the novel porous activated carbon from Triphala seed stones by chemical activation with zinc chloride at different carbonization temperature (400-700 °C) under the nitrogen gas atmosphere. The activated carbon was characterized by Fourier transform-infrared (FTIR) spectroscopy, Raman scattering and scanning electron microscopy (SEM). Nitrogen adsorption-desorption measurements was used to study the surface properties (effective surface areas, pore volumes and pore size distributions). The electrochemical measurements were performed in an aqueous 1 M sulphuric acid (H2SO4) solution in a three-electrode cell set up. Triphala seed stones-derived porous carbon materials with well-defined micro- and mesopores exhibit high specific surface area ranges from 878.7 to 1233.3 m2 g-1 and total pore volume ranges from 0.439 to 0.626 cm3 g-1. The specific capacitance obtained by electrochemical measurement experiment was 208.7 F g-1 at 1 A g-1. These results indicate that the prepared nanoporous activated carbon material from Triphala seed stones would have significant possibility as supercapacitor electrode material for high-energy-storage supercapacitor applications.

Nanostructured films formed on Zn during anodic oxidation in different carbonate-based electrolytes

Electrochemical generation of nanowire arrays by one-step anodic oxidation of Zn in carbonate-based electrolytes of different pH values is described. Zn foil was anodized in a mixture containing 5 mM Na2CO3 and 5 mM NaHCO3, as well as in pure Na2CO3 and NaHCO3 (both 10 mM). The morphology of anodic films was verified by FE-SEM. A special emphasis was put on the analysis of the composition of as-received nanomaterials by various techniques including XRD, XPS, UV–Vis, and Raman spectroscopy. Contrary to previous reports, we confirmed that the unknown phase of zinc carbonate with a formula of ZnCO3·H2O or Zn(HCO3)(OH) is formed at the Zn surface during anodization. The formation of ZnO resulting in more evident electrode passivation was also observed in the electrolytes containing sodium carbonates. The changes occurring during the thermal treatment of as-received materials were described based on TG, XPS, XRD, Raman, and nitrogen adsorption-desorption measurements. It was verified that, except for a several-fold increase in the active surface area, no significant changes in the wire-like morphology of the anodically generated product occur during its thermal conversion to ZnO. Finally, no noticeable differences in the photoelectrochemical performance of ZnO nanostructures formed in different electrolytes were observed.