Smaller Specific Surface Area Research Articles

Exploiting Photoinduced Atom Transfer Radical Polymerizations with Boron-Dopant and Nitrogen-Defect Synergy in Carbon Nitride Nanosheets.

Graphitic carbon nitrides (g-C3N4) possess various benefits as heterogeneous photocatalysts, including tunable bandgaps, scalability, and chemical robustness. However, their efficacy and ongoing advancement are hindered by challenges like limited charge-carrier separation rates, insufficient driving force for photocatalysis, small specific surface area, and inadequate absorption of visible light. In this study, boron dopants and nitrogen defects synergy are introduced into bulk g-C3N4 through the calcination of a blend of nitrogen-defective g-C3N4 and NaBH4 under inert conditions, resulting in the formation of BCN nanosheets characterized by abundant porosity and increased specific surface area. These BCN nanosheets promote intermolecular single electron transfer to the radical initiator, maintaining radical intermediates at a low concentration for better control of photoinduced atom transfer radical polymerization (photo-ATRP). Consequently, this method yields polymers with low dispersity and tailorable molecular weights under mild blue light illumination, outperforming previous reports on bulk g-C3N4. The heterogeneity of BCN enables easy separation and efficient reuse in subsequent polymerization processes. This study effectively showcases a simple method to alter the electronic and band structures of g-C3N4 with simultaneously introducing dopants and defects, leading to high-performance photo-ATRP and providing valuable insights for designing efficient photocatalytic systems for solar energy harvesting.

Electrocatalytic degradation of ofloxacin by self-doped copper/carbon cathode materials derived from waste printed circuit boards

Using residual copper metal from waste circuit boards, ordered carbon materials containing copper (PCBs-Cu-800) were synthesized by self-doping for the electrocatalytic degradation of ofloxacin (OFL). Although PCBs-Cu-800 has a smaller specific surface area, its efficiency in degrading OFL was higher than that of carbon materials without copper (PCBs-800), reaching 95.9 % within 2 h. The PCBs-Cu-800 electrode can generate a large amount of H2O2 in the initial stage of degradation, thereby increasing the amount of hydroxyl radicals (·OH) generated and removing OFL. Density functional theory simulations were used to calculate the adsorption energies of O2 on both materials, demonstrating that the self-doped copper model was more prone to O2 adsorption, and elucidating the excellent electrocatalytic performance of PCBs-Cu. The residual copper metal in the raw material is important in the electrocatalytic processes. This study presents an environmentally friendly catalytic material capable of effectively degrading OFL in solution using waste circuit boards and further expands the application scope of advanced electrochemical oxidation technology in wastewater treatment.

Biomass derived hard carbon materials for sodium ion battery anodes: Exploring the influence of carbon source on structure and sodium storage performance

Compared to the scarce resources of lithium-ion batteries, sodium ion batteries have gradually become an ideal carrier for large-scale energy storage systems due to their abundant raw material resources. In recent years, hard carbon as an anode material for sodium ion batteries has attracted much attention. Biomass materials have become an ideal hard carbon precursor due to their natural and renewable advantages. This article evaluates the effect of hard carbon derived from three types of biomass waste (peanut shell, coffee grounds, and sugarcane bagasse) on the electrochemical performance of sodium ion batteries through pre carbonization pyrolysis method. The three materials exhibit different structures and surface functional group contents. Compared with coffee grounds and sugarcane bagasse, peanut shell-derived hard carbon has lower structural ordering and smaller specific surface area, and exhibits a higher initial Coulombic efficiency of 53.84 %. The initial reversible capacity of the HC-P electrode is 203.6 mAh/g, and the Coulombic efficiency of the electrode is close to 100 % with a reversible capacity of 127.1 mAh/g and a capacity retention of 81.4 % after cycling 100 at 1C current. The excellent electrochemical properties of HC-P can be attributed to its higher C=O bond content, larger layer spacing and lamellar structure.

Hydrogen peroxide electrosynthesis using commercial carbon blacks as catalysts: the influence of surface properties and adsorption performance

AbstractBACKGROUNDSurface properties and adsorption performance of carbon materials play a crucial role in the electrochemical two‐electron oxygen reduction to produce H2O2. However, there is still a lack of in‐depth research on commercial carbon blacks in this area. Herein, four typical commercial carbon blacks (Acetylene black (AB), Ketjen black EC 600JD, Vulcan XC 72 and Black Pearls 2000) were used as cathode catalysts to generate H2O2. Surface chemistry and pore structure of electrodes of the four carbon blacks were systematically characterized, and their effects on H2O2 adsorption, electrochemical generation and degradation were investigated.RESULTSAmong the four carbon blacks, AB has the highest content of C–O–C/COOH and CO, which are active groups catalyzing the two‐electron oxygen reduction reaction to generate H2O2. AB has the lowest level of defects and highest degree of graphitization, and AB‐modified graphite felt electrode (AB‐Ele) has the largest average pore diameter, smallest specific surface area and smaller charge transfer resistance. H2O2 production using AB‐Ele is the largest and reaches 567.7 mg L−1 at 180 min under a current density of 5 mA cm−2, and only decreases by 17.6% after 10 repeated uses.CONCLUSIONOverall, rich oxygen‐containing functional groups such as C–O–C, COOH and CO, high degree of graphitization, suitable surface area and porosity as well as weak H2O2 adsorption performance are beneficial for the two‐electron oxygen reduction reaction to generate H2O2. AB‐modified graphite felt electrode exhibits good catalytic activity and reusability in H2O2 electrosynthesis, demonstrating promising application prospects. © 2024 Society of Chemical Industry (SCI).

Influence of shale reservoir properties on shale oil mobility and its mechanism

Given the tremendous potential for continental shale oil in China, many oilfields in the central and eastern parts of the country are involved in the exploration and development of shale oil resources. Besides engineering factors, shale oil mobility is the key to determining its commercial viability. This study explores the Hetaoyuan Formation in the Biyang Depression as an example to determine the influence of reservoir properties on the movable oil volume and its mechanisms. Multiple techniques were used, including displacement nuclear magnetic resonance (NMR), low-temperature nitrogen adsorption (LTNA), X-ray diffraction (XRD) bulk mineral analysis, and scanning electron microscopy (SEM), and the results suggest that large average pore diameter, high throat to pore ratio, single pore morphology, and small specific surface area can weaken the boundary layer effect and reduce the amount of adsorbed oil. Our observations reveal that compared to the dissolution pores and intergranular pores in brittle minerals, the intercrystalline pores in terrigenous clastic clay minerals are more affected by compaction. Furthermore, authigenic clay minerals notably block the intergranular pores in the interbedded sandstones. Clay minerals are identified as the main contributor to the specific surface area, with high clay mineral content enhancing the pore heterogeneity of the reservoir. Thus, positive shale oil mobility occurs in shale with a weak boundary layer effect, which is attributed to the high brittle mineral content, large average pore diameter, small specific surface area, single pore morphology, and reservoir homogeneity.

Unraveling the relationship between the mineralogical characteristics and lithium storage performance of natural graphite anode materials

Anode materials play critical role in cycling life of lithium-ion batteries in practical applications such as electric vehicles (EVs), portable electronic devices, and large-scale power grids. Natural graphite is one of the most successful anodes for commercial lithium-ion batteries due to its high theoretical capacity and low cost and low operating voltage. The mineralogical properties of graphite minerals have an important effect on the electrochemical performance of graphite anode, while their relationship remains ambiguous. In this work, natural graphite samples from four main graphite mining areas in China were selected as the research object, and their mineralogical characteristics were characterized by XRD, SEM, Raman, ICP, SEM, FIB, BET and other test methods. The properties of crystallinity, morphology, surface/phase defects, impurities, and specific surface area of graphite were studied. The results show that the cyclic stability of graphite is mainly affected by bulk defects and crystallinity, and the initial coulombic efficiency is mainly affected by surface defects and specific surface area. Graphite samples with appropriate surface defects, fewer volume defects, appropriate crystallinity, and small specific surface area have better electrochemical performance. It is hoped that this work should guide the manufacture and modification of the natural graphite anodes and promote its wider application in lithium-ion batteries.

Solid-state lithium batteries composed of hematite and oxide electrolyte

As Li-ion battery anode materials, two types of hematite (Fe2O3(big), Fe2O3(ultrafine)) were evaluated by using liquid electrolyte and oxide-based solid electrolyte. Although the anode using Fe2O3(ultrafine) with larger specific surface area showed a high initial reversible capacity in the liquid-electrolyte cell, there was a steep capacity decay in the cycling test. In the solid-electrolyte cell, we obtained very low reversible capacities of 40 mA h g−1 for the anode using Fe2O3(big) with smaller specific surface area. In contrast, the capacity of Fe2O3(ultrafine) anode was as high as 400 mA h g−1 at the 20th cycle. This is the first demonstration of charge–discharge reactions for Fe2O3 anode in oxide-based solid-state batteries. The Fe2O3(ultrafine) particles were dispersed relatively uniformly between solid electrolyte in the active layer, suggesting that the contact area between Fe2O3 and solid electrolyte becomes large. Consequently, Fe2O3(ultrafine) could benefit from larger contact area delivering the suitable reaction site for Li+ to improve the anode performance.

Characterization and utilization of cacao shell powder as a biofiller in natural rubber composite

The cacao shell, a by-product of the chocolate industry, is considered a waste and is normally discarded. This work aims to study the feasibility of using cacao shell powder (CSP) as a biofiller in rubber applications. The CSP was initially prepared, characterized, and incorporated into natural rubber (NR) at different loadings. Its reinforcement was compared with calcium carbonate (CaCO3) and carbon black (CB). The results showed that CSP had a relatively large average particle size (∼152 μm) and, thus, a very small specific surface area (4.5 m2/g). It mostly consisted of organic substances like cellulose, hemicellulose, lignin, proteins, etc. When incorporated into NR, both scorch time and optimal cure time decreased due to the existence of nitrogen-containing compounds, whereas hardness and modulus increased gradually with increasing CSP loading due to the dilution effect. At a given loading, CSP showed shorter scorch and cure times with greater hardness and modulus than CaCO3, indicating its greater cure activation ability and higher reinforcement magnitude. However, its reinforcement was far lower than that of carbon black. The maximum tensile strength was found at 30 phr of CSP loading, with a value of approximately 19.2 MPa, which was about 3% higher than that of CaCO3 but approximately 19% lower than CB. The findings suggest that, like other inert fillers, CSP can be employed for cost-reduction purposes in many applications where exceptionally high strengths are not essential, such as rubber bands, rubber flooring, rubber mats for livestock, etc.

Constructing Efficient CuO-Based CO Oxidation Catalysts with Large Specific Surface Area Mesoporous CeO2 Nanosphere Support.

CeO2 is an outstanding support commonly used for the CuO-based CO oxidation catalysts due to its excellent redox property and oxygen storage-release property. However, the inherently small specific surface area of CeO2 support restricts the further enhancement of its catalytic performance. In this work, the novel mesoporous CeO2 nanosphere with a large specific surface area (~190.4 m2/g) was facilely synthesized by the improved hydrothermal method. The large specific surface area of mesoporous CeO2 nanosphere could be successfully maintained even at high temperatures up to 500 °C, exhibiting excellent thermal stability. Then, a series of CuO-based CO oxidation catalysts were prepared with the mesoporous CeO2 nanosphere as the support. The large surface area of the mesoporous CeO2 nanosphere support could greatly promote the dispersion of CuO active sites. The effects of the CuO loading amount, the calcination temperature, mesostructure, and redox property on the performances of CO oxidation were systematically investigated. It was found that high Cu+ concentration and lattice oxygen content in mesoporous CuO/CeO2 nanosphere catalysts greatly contributed to enhancing the performances of CO oxidation. Therefore, the present mesoporous CeO2 nanosphere with its large specific surface area was considered a promising support for advanced CO oxidation and even other industrial catalysts.

Transient electrophoresis of a conducting cylindrical colloidal particle suspended in a Brinkman medium

The time-dependent electrophoresis of an infinitely cylindrical particle in an electrolyte solution, saturated in a charged porous medium after the sudden application of a transverse or tangential step electric field, is investigated semi-theoretically with an arbitrary double-layer thickness in an arbitrary direction relative to the cylinder. The time-dependent modified Brinkman equation with an electric force term, which governs the fluid flow field, is used to model the porous medium and is solved by using the Laplace transform technique. Explicit formulas, for the time-dependent electrophoretic velocity of the cylindrical particle in Laplace’s transform domain, have been derived for both axially and transversely when the uniform electric fields are imposed. They can also be linearly superimposed for an arbitrarily oriented relative to the electric field. Semi-analytical results for the electrophoretic velocities are presented as functions of the dimensionless elapsed time, the ratio of the particle radius to the Debye length, the particle-to-medium density ratio, and the permeability parameter of the porous medium. The results demonstrate, in general, that the growth of the electrophoretic velocities with the time scale are more slower for high permeability, and the effect of the relaxation time for unsteady electrophoresis is found to be negligible, regardless of the thickness of the double layer, the relative mass density or the permeability of the medium. The normalized transient electrophoretic velocities exhibit a consistent upward trend as the ratio of the particle radius to the Debye screening length increases. Conversely, they display a consistent downward trend as the particle-to-fluid density ratio increases, while all other parameters remain constant. The effect of the relaxation time for the transient electrophoresis is much more important for a cylindrical particle than for a spherical particle due to its smaller specific surface area.

Salt-Supported Nickel Oxides for Boosted Hydrogen Production: The Critical Role of Halogen.

Hydrogen production from organic waste by gasification and reforming technologies offers major benefits to both the environment and climate. The long-term stability and regeneration of the reforming catalyst are still the biggest challenges because of carbon deposition. Here we report a recyclable salt-supported nickel oxide NiO/NaX (X: F, Cl, Br) catalyst for effective autothermal reforming of the oxygenated volatile organic compound (OVOC) ethyl acetate to hydrogen. The optimal hydrogen selectivity achieved 82.0% at 650 °C and the durability reached 43 h. Interestingly, with the decreasing of halogen electronegativity (F > Cl > Br) in NaX, the corresponding hydrogen selectivity of the catalysts decreased. Although NiO/NaX catalysts possess a very small specific surface area and a dense microstructure, their catalytic performance is better than that of normal Ni-based catalysts loaded on high-specific-surface-area supports. Detailed investigations revealed the critical roles played by halogen during the reforming reaction. First, the strong electronegative halogen in NaX induced the formation of hydrogen bonds with the reactants and reaction intermediates, which may prolong the surface residence time of such species, thus ensuring efficient hydrogen production over small-specific-surface-area catalysts under high-temperature conditions. Second, the halogen of the support NaX weakening the Ni-O bonds of the exposed Ni atoms in NiO/NaX made it easier for NiO to be reduced to Ni0, thus reducing the reaction activation energy and prompting the rapid catalytic reaction. The strength of such metal-support interaction can be easily modulated by varying the halogen electronegativity. This study provides a new prospect for the design of innovative recyclable heterogeneous catalysts with low specific surface area but high activity.

High‐Coulombic‐Efficiency Hard Carbon Anode Material for Practical Potassium‐Ion Batteries

AbstractBiomass‐derived hard carbon (HC) has emerged as a promising candidate for anode materials of potassium‐ion batteries because of low cost and abundant raw materials. Whereas, the large specific surface area and high porosity of this type of HC often lead to inferior initial Coulombic efficiency (ICE) and unsatisfactory cycling stability. Herein, we report a coconut shell‐derived HC (CS‐HC) featuring an expanded interlayer spacing and small specific surface area. The CS‐HC delivers a reversible specific capacity of 280 mAh g−1 and an impressive ICE of 87.32 % at 50 mA g−1. In addition, it exhibits stable cycling performance (92.8 % capacity retention after 100 cycles at 50 mA g−1) and fast rate capability (∼280 mAh g−1 at 300 mA g−1). The ex situ Raman spectra characterization combined with cyclic voltammetry tests elucidate that the storage of potassium ions in the present HC is mainly achieved by (pseudo)capacitive behavior at the disordered defect sites along with minor contribution from the interlayer intercalation process. Finally, a full‐cell constructed with unprecycled CS‐HC anode and high‐voltage K2Mn[Fe(CN)]6 cathode demonstrates exceptional electrochemical stability and retains 90.6 % capacity after 100 cycles. This work reports a high‐performance HC anode material derived from low‐cost and sustainable biomass for practical potassium‐ion batteries.

Porous Carbon Cloth@CoSe2 as Kinetics‐Enhanced and High‐Loading Integrated Sulfur Host for Lithium–Sulfur Batteries

AbstractCarbon cloth (CC) possesses great potential as a sulfur host because of its excellent conductivity, flexibility, and easily modified free‐standing structure. However, the previous works do not take full advantage of CC except for the role of support and current collector. The smooth surface, small specific surface area, and poor binding force between coating materials and CC matrix are unfavorable for loading coating materials. The slow redox kinetics and low sulfur loading of sulfur cathodes still seriously restrict the development of Lithium–Sulfur (Li–S) batteries. Herein, the porous carbon cloth loading cobalt selenide (PCC@CoSe2) is constructed as an integrated sulfur host through a pore‐creating and selenylation strategy. The pore‐creating engineering greatly optimizes the 3D pore structure of CC to raise the sulfur and catalyst loading and provides enough space to accommodate the volume change of sulfur species. In addition, CoSe2 particles as nano‐catalyst units embedded in PCC can effectively adsorb‐catalyze polysulfides and improve the reaction kinetics. The resulting integrated sulfur cathode has realized the high‐efficiency polysulfide catalytic conversion and fast lithium ion migration, significantly enhancing redox kinetics and sulfur loading.

High-performance plastic-derived metal-free catalysts for organic pollutants degradation via Fenton-like reaction

The preparation of waste plastics-derived catalysts is an effective strategy for the waste reclamation. However, plastic-derived material is unsuitable for wastewater purification due to its small specific surface area (SSA) and inadequate active sites (such as N/O sites). Herein, we synthesized graphene-like nanosheets using g-C3N4 as the self-sacrificing soft template and plastic as the carbon precursor. Consequently, this strategy greatly promoted the efficiencies of the emerging organic pollutants degradation with the SSA and N content of the plastic-derived biochar increasing up to 1043.4 m2/g and 17.53 at.%, respectively. In detail, 100 % sulfadiazine (SD) removal could be achieved in 180 s via the activation of peroxymonosulfate (PMS) and the catalytic activity is far higher than previous research. Mechanism experiments corroborated that such a striking performance was attributed to the generation of SO4•−, O2•− and 1O2. Meanwhile, kinds of plastic precursors, even medical waste (i.e., masks, gauze, operating caps and degreasing cotton) were also applicable. And the practical application of the plastic-derived catalyst was further demonstrated by treating pollutants in a continuous flow mode with in situ fabricated membrane. This work provides valuable insights into waste plastics processing and water pollutants removal.

High-performance rechargeable aqueous zinc-iodine batteries via a dual strategy of microporous carbon nanotubes for cathodic iodine immobilization and modified separator

Compared with lithium-ion battery, aqueous rechargeable zinc-iodine is of interest due to their high safety and low cost. Unfortunately, the host material's low conductivity, small specific surface area, shuttling effect, and high soluble iodine species (I2, I-, and I3-) are inhibiting its wide development. In this work, a dual strategy of fixing iodine active material with nanotubular microporous carbon (MCN) and modified cotton fiber separator (MCN@CF) is employed to solve the above-mentioned problem. The Zinc-ion batteries (ZIBs) assembled with an MCN/I2 cathode and MCN@CF separator show up to 162 mA h g-1 of reversible initial capacity with 85 % capacity retention at 100 mA g-1 after 100 cycles. Moreover, besides featuring excellent long-term cyclability, MCN@CF battery delivers a Coulombic efficiency of 99 % over 2000 cycles with a current density of 1 A g-1. This study would lead to opening of a new paradigm for the development of highly reversible aqueous rechargeable ZIBs.

Effect of pyrolysis temperature and hydrothermal activation on structure, physicochemical, thermal and dye adsorption characteristics of the biocarbons.

In this study, the possibility of using sawdust from mixed woods to obtain biocarbons in the pyrolysis and steam activation using microwave radiation as an energy source was investigated. Biocarbons were characterized based on the results of N2 adsorption, thermogravimetric analysis (TGA), Fourier spectroscopy (ATR-FTIR), and Raman spectroscopy. Surface characterization was performed by Boehm titration and pHpzc determination. The adsorption capacity of methylene blue (MB) and methyl orange (MO) was studied. It was proved that the pyrolysis temperature and hydrothermal activation increased the biocarbons structural, surface and adsorption parameters of the obtained biocarbons. The amorphous materials of small specific surface area with a significant share of micropores were obtained. The steam activation resulted in significant development of the porous structure (to SBET =729.2 m2 /g and Vp =0.36 cm3 /g). The presence of functional groups, mainly phenolic ones, and pHpzc values indicating a potential for adsorption applications regarding MO and MB were found. The highest sorption capacity concerning MB (qe =122.8 mg/g) and MO (qe =99.1 mg/g) was observed for the steam-activated biocarbon BC-800MW . Using microwave energy hydrothermal activation proved very efficient, resulting in significant surface area and porosity development with a small loss of carbon matter.

Efficient Decontamination: Caffeine/Triclosan Removal using Rice Husk in Batch and Fixed-Bed Columns

Abundant, easily accessible, and low-cost agro-industrial residues represent attractive alternatives for removing emerging contaminants from water. In this work, the aqueous adsorption of caffeine/triclosan onto rice husk (RH) was studied in batch and continuous processes. For this purpose, adsorbents with three particle size ranges (120–150, 300–600, 800–2000 µm) were prepared and evaluated. The composition, structure, surface morphology, functionality, and specific surface area of the RH biosorbents were determined. This characterization revealed that RH primarily consists of lignin, cellulose, and hemicellulose, making up to 80.1% of its composition. RH also exhibited an irregular surface, with several functional groups (OH, C=O, CH, C=C, C-OH), and a relatively small specific surface area (1.18 m2/g). Batch tests were carried out using different RH sizes, doses (1–50 g/L), and contact times (5–300 min), using 20 mL of caffeine/triclosan solutions (30 mg/L). Tests were conducted to fit the most adequate kinetics and isotherm models. The optimal doses (g/L) for caffeine and triclosan removal were 4.5 and 1.5 with small RH, 8.5 and 2.5 with medium RH, and 50.0 and 10.0 with large RH, respectively. The optimal contact times for all three particle sizes were 180 and 60 min. Triclosan removal was greater than that of caffeine (2.5–25.5%) with all three particle sizes, requiring less adsorbent (2.5–5.0 times) and shorter times (3 times). The experimental data fit better the Sips isotherm and Elovich kinetics models. The small (120–150 µm) particles achieved the highest caffeine/triclosan batch adsorption capacities (6.3/28.6 mg/g). Continuous tests were performed on fixed-bed columns of 1 cm in diameter, packed with 4, 5, and 8 cm of RH, operated with hydraulic loading rates between 2 and 4 m3/m2day. Small particles also reached the highest adsorption capacity in the removal of caffeine (352.7 mg/L) and triclosan (3797.2 mg/L), and the experimental data were well-fitted to the Bohart–Adams model. The research results not only demonstrate the effective removal of contaminants but also illustrate the versatility and applicability of rice husk in various conditions and systems.

Synthesis of small size lead-free Cs3Bi2xSb2−2xBr9 solid-solutions using a spatially confined growth method for efficient photocatalytic CO2 reduction

The small size lead-free Cs3Bi0.6Sb1.4Br9 solid-solution spatially confined in MCM-41 molecular sieve shows an outstanding performance for photocatalytic CO2 reduction to CO.

Mitigating hydrogen gas evolution in high nickel cathodes using single-crystalline NCM particles

Single-crystal nickel cobalt manganese oxide cathodes significantly reduce hydrogen gas evolution due to their smaller specific surface area and enhanced structural stability.

Citric acid-assisted synthesis of FeFe(CN)6 with reduced defects and high specific surface area for aqueous zinc–sodium hybrid batteries

With citric acid as an additive, low-defect C-FeFe(CN)6 with small grain size and high specific surface area was successfully prepared using a controlled crystallization method.