Desirable Surface Area Research Articles

Fabrication of Fe3O4-incorporated MnO2 nanoflowers as electrodes for enhanced asymmetric supercapacitor performance.

Manganese dioxide (MnO2) is considered a promising aspirant for energy storage materials on account of its higher theoretical capacitance along with low capital cost. However, its performance is generally limited by its poor lifespan and intrinsic conductivity. In this study, MnO2-incorporated iron oxide (Fe3O4) nanoflowers were synthesized through a facile hydrothermal route and their electrochemical performance was probed. The surface composition and morphology of the as-synthesized samples were confirmed using X-ray diffraction, X-ray photoemission spectroscopy, and field emission scanning microscopy. The nanoflower-like structure and synergistic effect between the two oxides of the as-prepared MnO2@Fe3O4 nanocomposite electrode result in desirable surface area and intrinsic conductivity. Owing to its higher surface area and electrical conductivity, the MnO2@Fe3O4 nanoflower-like nanocomposite exhibits an enhanced specific capacitance (Cs) of 1651 F g-1 (1 A g-1) in a three-electrode test cell, which is two-fold higher than those of pristine Fe3O4 and MnO2. In addition, an asymmetric supercapacitor (ASC) was readily constructed by sandwiching a cellulose membrane (separator) between MnO2@Fe3O4 (cathode) and activated carbon (anode). Significantly, the ASC displayed a high Cs of 131 F g-1 (1 A g-1) along with a pretty high cycling stability of 96% over 5000 cycles at 15 A g-1 and a high energy density of 46.6 Wh kg-1 at 0.8 kW kg-1. These results demonstrate the significant potential of the MnO2@Fe3O4 nanoflower ASC device for state-of-the-art futuristic advanced energy storage applications.

In situ preparation of an anatase/rutile-TiO2/Ti3C2T x hybrid electrode for durable sodium ion batteries.

Herein, a facile one-step method is developed to in situ prepare crystalline anatase and rutile TiO2 nanocrystals on Ti3C2Tx by regulating the metastable Ti ions. The combination of TiO2 nanocrystals and Ti3C2Tx not only introduces extensive accessible sites for Na+ storage, but also promotes the charge transport by efficiently relieving the collapse of Ti3C2Tx. Compared with pristine Ti3C2Tx, the optimized TiO2/Ti3C2Tx hybrid electrode (anatase/rutile-TiO2/Ti3C2Tx, A/R-TiO2/Ti3C2Tx) exhibits a desirable specific surface area (22.5 m2 g−1), an ultralow charge transfer resistance (42.46 Ω) and excellent ion diffusion (4.01 × 10−14). Remarkably, rich oxygen vacancies are produced on TiO2/Ti3C2Tx which is beneficial to enhance the insertion/de-insertion of Na+ during the charge/discharge process. As a result, the A/R-TiO2/Ti3C2Tx delivers a high average capacity of 205.4 mA h g−1 at 100 mA g−1 and a desirable capacitance retention rate of 84.7% can be achieved after 600 cycles at 500 mA g−1.

Modification of mesoporous structure of silver-doped bioactive glass with antibacterial properties for bone tissue applications

Silver-containing mesoporous bioglasses powders with SiO2–CaO–P2O5–Ag2O composition have been successfully synthesized by sol-gel and evaporation-induced self-assembly (EISA) methods in presence of various amounts of surfactant (Pluronic-F127). The morphology and crystal structure of the powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD). Also, the textural properties of samples have been evaluated by adsorption-desorption, Langmuir and BET methods. Accordingly, powders had a smooth surface morphology with cubic mesoporous structure and a desired surface area and pore volume. The in vitro bioactivity was assessed by SEM, XRD and Fourier transform infrared spectroscopy (FTIR) analyses. All samples enhance the formation of HA after soaking the material in simulated body fluid (SBF) solution. The antibacterial property of samples was evaluated to investigate the effect of silver content in chemical composition. The results showed an adequate antibacterial activity of the samples against Escherichia coli, Salmonella and Listeria monocytogenes.

Enhanced catalysis through structurally modified hybrid 2-D boron nitride nanosheets comprising of complexed 2-hydroxy-4-methoxybenzophenone motif

Tuning the structural architecture of the pristine two dimensional hexagonal boron nitride (h-BN) nanosheets through rational surface engineering have proven advantageous in the fabrication of competent catalytic materials. Inspired by the performance of h-BN based nanomaterials in expediting key organic transformations, we channelized our research efforts towards engineering the inherent surface properties of the exclusively stacked h-BN nanosheets through the incorporation of a novel competent copper complex of a bidentate chelating ligand 2-hydroxy-4-methoxybenzophenone (BP). Delightfully, this hybrid nanomaterial worked exceptionally well in boosting the [3 + 2] cycloaddition reaction of azide and nitriles, providing a facile access to a diverse variety of highly bioactive tetrazole motifs. A deep insight into the morphology of the covalently crafted h-BN signified the structural integrity of the exfoliated h-BN@OH nanosheets that exhibited lamellar like structures possessing smooth edges and flat surface. This interesting morphology could also be envisioned to augment the catalysis by allowing the desired surface area for the reactants and thus tailoring their activity. The work paves the way towards rational design of h-BN based nanomaterials and adjusting their catalytic potential by the use of suitable complexes for promoting sustainable catalysis, especially in view of the fact that till date only a very few h-BN nanosheets based catalysts have been devised.

Honeycombed activated carbon with greatly increased specific surface by direct activation of glucose for supercapacitors

In the production of activated carbons (ACs), glucose as a precursor is prone to producing the graphitic char intermediates after carbonization, which are difficult to be activated in the subsequent activation. In order to obtain a desirable specific surface area, either twice activation after carbonization or hydrothermal treatments of glucose before activation is applied. In this research, the direct activation of glucose has been executed to produce honeycombed ACs via deoxygenation of the glucose precursor in the KOH aqueous solution for appropriate time at room temperature. It is found that when glucose is subjected to the alkaline circumstance, dehydration and polymerization reactions increase the C/O ratio while the degradation and oxidation decrease the C/O ratio. The AC from the deoxygenated product with the highest C/O ratio has a superior specific surface area of 1912 m2 g−1 which is much higher than 130 m2 g−1 for the AC by the conventional two-step method. The Honeycombed morphology and the specific surface increased by one order of magnitude lead to good performance of 268 F g−1 in the KOH and 24.5 Wh kg−1 in the KBr electrolyte.

Statistical modeling and mechanistic pathway for methylene blue dye removal by high surface area and mesoporous grass-based activated carbon using K2CO3 activator

In this study, biomass of grass waste (GW) was utilized as sustainable precursor to produce highly porous activated carbon (GWAC) with mesoporosity using a K2CO3-assisted pyrolysis approach and tested for its methylene blue (MB) dye adsorption properties. The prepared GWAC was characterized using the various techniques of specific surface area (SSA), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), X-ray diffractometer (XRD), thermogravimetric analysis (TGA), and Fourier Transform Infrared (FT-IR) spectrophotometer. The characterization results indicate the successful conversion of GW into mesoporous GWAC with high and desirable surface area of 1245.6 m2/g. The adsorptive performance of GWAC towards MB uptake was evaluated. To attain higher performance of the activated carbon for MB adsorption, the adsorption key parameters such as GWAC dosage (A: 0.04–0.06 g/L), pH (B: 4–10), temperature (C: 30–60 °C), and time (D: 5–15 min) were optimized using the Box–Behnken design (BBD) method. The adsorption equilibrium data were accurately described by the Langmuir model, where the adsorption capacity (qm; 364.2 mg/g) was recorded at the optimized process temperature of 45 °C. The present research also examined the mechanisms associated with the removal of MB using GWAC and observed the contribution of various MB-GWAC surface interactions (e.g., electrostatic, π-π, and H-bonding interactions). The present investigation shows the utility and effectiveness of GW biomass based activated carbon due to its favorable mesoporosity and cationic dye uptake in aqueous media.

Highly active solid oxide acid catalyst for the synthesis of benzaldehyde glycol acetal

A series of composite metal oxide catalysts, namely CeMnTiO, CeCoTiO, and CeFeTiO, were prepared by sol-gel method, and their physicochemical properties were characterized by various techniques, viz. SEM, XRD, XPS, and NH3-TPD. Their desirable acidity and surface area were suitable for the acid-catalyzed acetalization reaction of benzaldehyde (BzH) with ethylene glycol (EG). In particular, CeFeTiO catalyst exhibited superior activity and excellent durability, leading to an acetal yield of 96.8 %, which was in close agreement with the optimal yield (96.95 %) predicted by the response surface methodology (RSM) based on a Box-Behnken design (BBD). Moreover, a kinetic study under the optimal reaction conditions showed that the acetalization reaction was second-order with an active energy (Ea) of 46.65 kJ/mol. Results revealed that CeFeTiO catalyst had high efficiency to surpass conventional Amberlyst catalysts for acetalization reactions.

Control of surface area and conductivity of niobium-added titanium oxides as durable supports for cathode of polymer electrolyte fuel cells

Niobium-added titanium oxide is a promising candidate as a substitute carbon support for cathodes of PEFCs. Nb-added TiO2 can act as a support for platinum nanoparticles to enhance the oxygen reduction reaction (ORR) activity and durability under acidic conditions. Nb-added TiO2 supports with the desired surface area (10–130 m2 g−1) and conductivity (10−7–10−2 S cm−1) were prepared by changing the amount of Nb and the heat treatment conditions. First, we conducted a systematic investigation with changes in the amount of niobium addition, heat-treatment temperature, and time under a pure hydrogen atmosphere to reveal the physicochemical factors that govern the surface area and conductivity. Finally, we successfully proposed a procedure to prepare highly durable Nb-added TiO2 supports with the desired surface area and conductivity by controlling the amount of niobium addition, heat-treatment temperature, and time under hydrogen. The charges of the double layer were almost unchanged after 5000 cycles of an accelerated durability test (ADT).

Spirulina-templated porous hollow carbon@magnetite core-shell microswimmers

Magnetic helical micro/nanoswimmers, one swimming micro/nanorobots inspired by the E. coli bacterium, have attracted much attention of the community. Using low-strength rotating magnetic fields, they can be effectively actuated and perform controlled locomotion in various fluids, and are therefore envisioned for advanced biomedicine, precise micromanipulation and efficient environmental purification. In this study, we demonstrate a core-shell-structured hollow helical microswimmer that possesses an inner core of porous carbon and an outer shell aggregated by mesoporous spindle-like magnetite nanoparticles (NPs). The fabrication of it is achieved via a straightforward Spirulina-based biotemplating process, featuring high yield and low cost. The obtained microswimmers integrate desirable photothermal attributes and specific surface areas (SSA) from their magnetite-carbon composition and porous hollow architectures. Here these two functions are harnessed for bacterial killing and heavy metal ion collection (or cargo loading). Furthermore, such swimmers exhibit high magnetic saturation, advantageous superparamagnetic characteristics and robust swimming performance. The results of this study suggest a multifunctional helical microswimmer suitable for photothermal antibacterial therapy, biological detoxification and targeted delivery in the gastrointestinal (GI) tract.

Simultaneous Multication Exchange Pathway to High-Entropy Metal Sulfide Nanoparticles.

High entropy materials, which contain a large number of randomly distributed elements, have unique catalytic, electrochemical, and mechanical properties. The high configurational entropy of the randomized elements drives the formation of high entropy materials; therefore, high temperatures and quenching are typically required to stabilize them. Because of this, colloidal nanoparticles of high entropy materials are difficult to synthesize and remain rare, despite their desirable high surface areas and solution dispersibilities. Here, we introduce simultaneous multication exchange as an alternative low-temperature pathway to colloidal nanoparticles of high entropy materials. Roxbyite Cu1.8S nanoparticles react with a substoichiometric mixture of Zn2+, Co2+, In3+, and Ga3+ to produce nanoparticles of the high entropy metal sulfide Zn0.25Co0.22Cu0.28In0.16Ga0.11S. The Zn0.25Co0.22Cu0.28In0.16Ga0.11S nanoparticles are thermally stable, and exchange reactions using fewer cations do not produce the high entropy phase. The use of colloidal nanoparticle cation exchange as a synthetic platform provides both entropic and enthalpic driving forces that, in addition to configurational entropy, enable the formation of high entropy phases at solution-accessible temperatures.

Statistical Modeling and Kinetic Studies on the Adsorption of Reactive Red 2 by a Low-Cost Adsorbent: Grape Waste-Based Activated Carbon Using Sulfuric Acid Activator-Assisted Thermal Activation

The efficiency of activated carbon produced from grape waste as a low-cost, nontoxic, and available adsorbent to remove Reactive Red 2 from aqueous solution has been investigated. The prepared activated carbon has been characterized by FTIR, SEM, and BET. The results of characterization indicate the successful conversion of grape waste into mesoporous AC with desirable surface area consist of different functional groups. The results of statistical modeling displayed high [Formula: see text] value of 0.97% for dye removal that shows the developed model has acceptable accuracy. The effect of independent variables indicated that the highest adsorption (96.83%) obtained at pH 3, adsorbent dosage of 12.25 g/L, and initial dye concentration of 100 mg/L when the adsorption time was 90 min. The results of isotherms modeling showed that the data fit well with the Langmuir (type II). The kinetic studies using pseudofirst-order and pseudosecond-order models pointed out that the type (I) of pseudosecond-order kinetic model provided the best fit to the adsorption data. Parameters of thermodynamics including Gibbs energy ([Formula: see text]) and [Formula: see text] were calculated. The values of [Formula: see text] indicated that the dye adsorption of RR2 is spontaneous. The agricultural wastes due to special points such as low-cost, availability, and high ability to produce an adsorbent with high efficiency to remove dye can be proposed for water and wastewater treatment.

Trace-Level Fluorination of Mesoporous TiO2 Improves Photocatalytic and Pb(II) Adsorbent Performances.

Fluorination is an effective way of tuning the physicochemical property and activity of TiO2 nanocrystallites, which usually requires a considerable amount of hydrofluoric acid (or NH4F) for a typical F/Ti molar ratio, RF, of 0.5-69.0 during synthesis. This has consequential environmental issues due to the high toxicity and hazard of the reactants. In the present work, an environmentally benign fluorination approach is demonstrated that uses only a trace amount of sodium fluoride with an RF of 10-6 during synthesis. While it maintained the desirable high surface area (102.4 m2/g), the trace-level fluorination enabled significant enhancements on photocatalytic activities (e.g., a 56% increase on hydrogen evolution rate) and heavy metal Pb(II) removal (31%) of the mesoporous TiO2. This can be attributed to enriched Ti3+ and localized spatial charge separation due to fluorination as proved by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR), and density functional theory (DFT) analyses.

A review on carbon and non-precious metal based cathode catalysts in microbial fuel cells

Microbial fuel cells, an emerging technology has been paid a great attention in recent years, due to its unique advantages in treating wastewater to portable water, together with the generation of useful electricity, with the help of bio-active anodes and electrochemical cathodes, simultaneously. When applying this technology in a practical scale, the indigenous bacteria present in the wastewater catalyze the breakdown of organic matter in the anode compartment, with generation of electrons and in the cathode compartment an oxidant, usually the oxygen present in the air, take the electron and reduce to water (oxygen reduction reaction, ORR). An ideal ORR catalyst should be highly active, durable, scalable, and most importantly it should be cost effective. Generally, platinum-based catalyst is utilized, however, due to the high cost of Pt based catalysts, many cheap, cost effective catalyst have been identified as efficient ORR catalyst. Carbon based catalysts known to possess good electronic conductivity, desirable surface area, high stability, together when doped with heteroatoms and cheap metals is found to remarkably enhance the ORR activity. Although a lot of research has been done in view of developing carbon based cheap, cost-effective catalysts, still their collective information has not been reviewed. In this article we anticipate reviewing various non-precious metal and metal-free catalysts that are synthesized and investigated for MFCs, factors that affect the ORR activity, catalyst designing strategies, membranes utilized for MFCs, together with the cost comparison of non-precious and metal-free catalysts with respect to Pt based catalysts have been summarized. We anticipate that this review could offer researchers an overview of the catalyst developed so far in the literatures and provides a direction to the young researchers.

Nanostructured electrocatalysts for electrochemical carboxylation with CO2

AbstractElectrocarboxylation of organic compounds with CO2, using electrons as clean reductants under ambient conditions, is a readily available and efficient method to transform organic molecules to high‐value carboxylates with nearly 100% atom efficiency. However, the selectivity of the electrochemical reactions is still limited, the real reactive sites for electrocarboxylation; the relationship between the geometrical/electronic structure and the catalytic performance is unclear. Meanwhile, the development of nanomaterials brings new prospects and orientation for the electrocarboxylation due to the desired high surface area and abundant active sites. In this review, we focus on the summary of recent work on the design of nanostructured electrocatalysts and the reaction mechanisms of electrocarboxylation. Mainly, we highlight the influence of different electrocatalyst structures on a variety of organic molecule adsorption. Finally, some challenges were proposed to explore advanced electrocatalysts and the deeper reactive mechanism for electrocarboxylation.

Clean utilization of palm kernel shell: sustainable and naturally heteroatom-doped porous activated carbon for lithium–sulfur batteries

Lithium–sulfur batteries (LSBs) have received much concern as emerging high-power energy storage system. Nevertheless, the low conductivity of sulfur and polysulfide shuttle results in low rate capability and rapid capacity decay, which seriously limit its commercial application. Here, facile, sustainable and cost-effective strategy for preparing heteroatom-doped porous activated carbon (PAC) derived from biomass palm kernel shell (PKS) was developed for high-performance LSB applications. The presence of N, P and S heteroatoms with modification of the surface polarity brings about large amounts of active sites and improved adsorption property compared to those of common carbon materials. The PAC sample possesses desirable specific surface area (SSA) (2760 m2·g−1) as well as pore volume (1.6 cm3·g−1). Besides, the good electrical conductivity of PAC endows the material with excellent rate performance. The PAC-S electrode with a 60% of sulfur loading has a desirable first discharge capacity (1045 mAh·g1, 200 mA·g−1) with superb discharge capacity (869.8 mAh·g−1, 100th cycle) and cyclability (312.6 mAh·g−1, 800 mA·g−1, 1000th cycle), which can be mainly ascribed to its unique porous properties and the good conductivity of PAC.

Catalytic Hydrothermal Carbonization Treatment of Biomass for Enhanced Activated Carbon: A Review

Biomass for activated carbon production has had been gaining interest in a wide variety of applications such as water filtration, gas adsorption, and electrochemical devices as a renewable carbon source while meeting desired porosity, surface area, conductivity, and stability requirements. Activated carbon production has been extensively investigated, proving to provide high performance in applications including electrochemical devices. Hydrothermal carbonization (HTC) has shown potential as a pretreatment method for activated carbon production, especially when surface functionalization is desired. However, research into catalytic HTC is still limited. In this review, the processing methods used to convert biomass waste products into high value activated carbon are briefly reviewed, with a focus on recent progress in catalytic HTC as a pretreatment method to activated carbon. Areas of interest for catalytic HTC for activated carbon production are identified. Recent studies have found that the use of catalysts enhances the degree of carbonization, surface modification, and introduction of key heteroatoms significantly augmenting the performance of activated carbon. With further development of catalytic HTC technology, more competent carbon material for electrochemical devices can be produced cost-effectively and move towards meeting the ever-increasing demands of activated carbons for high-performance electrochemical devices.

One-dimensional graphene for efficient aqueous heavy metal adsorption: Rapid removal of arsenic and mercury ions by graphene oxide nanoribbons (GONRs)

There is a knowledge gap for the application of one-dimensional graphene in the adsorption process. Our hypothesis was based on the fact that graphene oxide nanoribbons (GONRs) as one-dimensional graphene with more desired edges and specific surface area than other carbonaceous nanomaterials have more oxygen containing functional groups (active sites) on their edges and basal planes and therefore are more capable in adsorption of pollutants. In this regard, we synthesized GONRs by unzipping of multi-walled carbon nanotubes (MWCNTs) and investigated the adsorption behavior of GONRs by ultrasonic-assisted adsorptive removal of As(V) and Hg(II) ions from aqueous solution. The obtained results showed that As(V) ions are more favorably adsorbed onto the GONRs than Hg(II) ions and with increasing initial As(V) and Hg(II) ions concentration to 300 ppm, the equilibrium adsorption uptake of the synthesized GONRs increases to 155.61 and 33.02 mg/g for As(V) and Hg(II) ions, respectively through a rapid separation process in just 12 min. Also, three kinetic models and Freundlich and Langmuir adsorption isotherms were applied to evaluate the obtained experimental results. Our findings highlight the potential application of GONRs as one-dimensional graphene adsorbent with more desired edges than MWCNTs and graphene oxide (GO) and high adsorption capacity for selective removal of heavy metals.

Synthesis of C-doped TiO2 by sol-microwave method for photocatalytic conversion of glycerol to value-added chemicals under visible light

C-doped TiO2 photocatalyst synthesized using a one-step sol-microwave method with microcrystalline cellulose as the carbon source to achieve TiO2 of desirable visible light absorption, cluster size, surface area and band gap was applied in the photocatalytic oxidation of glycerol under visible light to produce value-added chemicals, for the first time. An increase in microwave irradiation time from 0 to 20 min reduced the anatase crystal size but increased the surface area, pore volume and pore radius. Carbon coupled with microwave treatment produced Ti3+ and oxygen vacancies in the TiO2 lattice of the C-doped TiO2 which yielded improved performance of the photocatalysts. For example, a cellulose loading at 10 % (i.e. 10 % Cel-TiO2(4-MW)) provided the highest photo-conversion of glycerol (67.5 %) and highest yields of glyceraldehyde (10.0 %), dihydroxyacetone (7.4 %), formic acid (49.0 %) and acetic acid (1.8 %). On the other hand, excess residual carbon on TiO2 surface (e.g. 20 % Cel-TiO2(0-MW)) retarded the activity of the photocatalyst.

Synthesis of coryphantha elephantidens-like SnO2 nanospheres and their gas sensing properties

In this work, coryphantha elephantidens-like SnO2 with porous structures were prepared successfully by a simple hydrothermal route, through adjusting the temperature of hydrotherm. Its morphology was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET). Compared to the regular nanospheres, the coryphantha elephantidens-like SnO2 nanospheres had obviously higher gas-sensing response, owing to the special structure with large specific surface area (161.16 m2 g−1). It surprised us that the coryphantha elephantidens-like SnO2 sensor could easily distinguish between ethanol and acetone, whose chemical property were similar. Moreover, it also exhibited wide measurement range, fast response speed (less than 10 s) and good repeatability at a low temperature (180 °C) to ethanol. The desirable specific surface area and pore volume were conducive to molecules adsorption and diffusion, which were believed to be the major cause of the improvement of gas sensing performance.

High-performance nitrogen-doped hierarchical porous carbon derived from cauliflower for advanced supercapacitors

Nitrogen-doped hierarchical porous carbon is successfully synthesized from cauliflower with unique structure by a simple pyrolysis process, including a pre-carbonization step of cauliflower and a KOH-activated step of carbonization product. According to this pyrolysis strategy, the pre-carbonization product at 450 °C basically keeps the original structure of cauliflower, beneficial to the deep and uniform activation at 700 °C and the formation of 3D interconnected network framework. The as-prepared sample (NPCC2-700) shows desirable specific surface area of 2604.7 m2 g−1, large pore volume, and abundant micropores and mesopores. Combined with the high content of active heteroatoms, NPCC2-700 exhibits high specific capacitance of 311 F g−1 at 1 A g−1 and 250 F g−1 at 50 A g−1 in 6M KOH electrolyte. Meanwhile, the excellent rate performance and long-term cycling stability can be achieved for NPCC2-700. Furthermore, the energy density of the assembled symmetric supercapacitor based on NPCC2-700 electrodes is as high as 20.5 Wh kg−1 at a power density of 448.8 W kg−1 in 1 M Na2SO4 solution.