Sulfonic Acid Groups Research Articles

Novel sulfonated polyaniline/graphene oxide electrode with high cycling stability for all-solid-state flexible supercapacitors

Polyaniline (PANi) has high theoretical specific capacitance by storing energy through redox reactions and thus is widely used in supercapacitors. However, the skeleton of PANi expands and contracts during the process of ion inhalation and exfoliation, which leads to a decrease in electrochemical performance. To solve this problem, we graft the sulfonic acid group onto the PANi backbone via a borate ester bond, which serves as a proton reservoir to provide protons for PANi to undergo redox reactions and provide pseudocapacitance. SPANi is then polymerized in situ on graphene oxide (GO), and its comprehensive performance of the electrode is further enhanced by designing ordered structures and synergistic interactions. The SPANi5/GO5 composite that are created in-situ have a fantastic specific capacitance of 460.56 F g−1 at 1 A g−1 and maintained 85.19% of the primary capacitance after 10,000 cycles. The device is assembled with PAAM/H2SO4/GO as the gel electrolyte, which achieves a specific capacitance of 137.75 F g−1, and the capacitance is retains at 90.74% after 10,000 cycles. The supercapacitor exhibits a large energy density of 13.76 Wh kg−1 when the power density is 200.27 W kg−1. The present study presents a novel and efficient approach for the fabrication of high-performance supercapacitor electrodes.

Enhancing proton exchange membrane water electrolysis performance: Impact of iridium oxide catalyst ink dispersing methodology

Iridium oxide (IrO2) is the most successful catalyst for triggering oxygen revolution reactions in proton exchange membrane water electrolyzers (PEMWE). However, conventional ultrasonic methods for ink dispersion often result in ink instability, catalyst aggregation, and sedimentation. To address these issues, we investigate the effects of the dispersion type, treatment time, and ionomer-addition sequence on the catalytic performance. Ball-milling procedure prepares a more stable catalyst ink and achieves a larger electrochemical surface area (ECSA) than ultrasonic method. Extending the ball-milling time to 12 h improves the ink stability (absorbance change rate ∼0.6 % h−1); however, over-processing causes the thickest catalyst layer, leading to an enhanced mass transport resistance. Moreover, treating an ionomer with IrO2 causes the substitution of sulfonic acid groups by carboxylic acid groups and reduces the repulsive force in colloidal particles, resulting in poor ink stability, low proton conductivity, and small ECSA. Therefore, adding ionomer after ball milling is recommended for the preparation of a stable ink with high catalytic performance. The membrane electrode assembly prepared using this procedure exhibits an improved performance of 1.70 A cm−2 at 1.7 V, compared with that prepared using ultrasonic methods. This work provides crucial guidance of ink preparation for large-scale production of PEMWEs.

Multistimuli-responsive tetraphenylethene molecular switches displaying acid-sensing, photochromism, and metal ion detection properties

Aggregation-induced emission (AIE) smart materials with multiple stimulus responses have a wide range of applications. Here, a series of tetraphenylethylene (TPE) derivatives, TPEN1S3, TPEN2S2, TPEN3S1 were synthesized. The sensitivity of molecules to pH, UV light, and metal ions could be effectively tuned by modulating the ratio of amino to sulfonic acid groups. These TPE derivatives exhibited yellow emissions in aggregated state due to the AIE characteristics. Acidification conversion of the NH2 groups to NH3+ for three molecules induced the suppression of intramolecular charge transfer (ICT), which resulted in a 72–102 nm blue shift in the fluorescence emission. Solid powders of these compounds exhibited reversible protonation-deprotonation process induced by HCl/NH3·H2O vapor. TPEN1S3, TPEN2S2 and TPEN3S1 in solution could be photoactivated and emit blue fluorescence (ca. 482 nm, 475 nm, and 480 nm). Photocyclo-dehydrogenation reactions of compounds were triggered by the UV irradiation and the maximum cyclization ratios could reach 12%, 66%, and 50%, respectively. Protonation of NH2 group significantly enhanced the rate of the photocyclo-dehydrogenation reaction. Furthermore, the solid powders of protonated compounds displayed pronounced reversible photochromic properties due to the generation of cyclization intermediate. In addition, TPEN1S3, TPEN2S2, and TPEN3S1 exhibited responsiveness to a diverse range of metal ions. Specifically, the TPEN2S2 molecule functioned as a photo sensor for Li + ions with a blue shift in fluorescence emission. The limit of detection (LOD) value was 0.679 μM. These multiple stimuli-responsive AIE molecules hold significant potential for use in advanced photo-controlled patterning, encryption applications, and the detection of metal ions.

Taurine-Functionalized Carbon Nanotubes as Electrode Catalysts for Improvement in the Performance of Vanadium Redox Flow Battery

The vanadium redox flow battery (VRFB) is a highly favorable tool for storing renewable energy, and the catalytic activity of electrode materials is crucial for its development. Taurine-functionalized carbon nanotubes (CNTs) were prepared with the aim of augmenting the redox process of vanadium ions and enhancing the efficiency of the VRFB. Sulfonated CNTs were synthesized through a simple modification process in a taurine solution and used as electrocatalysts for redox reactions involving VO2+/VO2+ and V2+/V3+. The SO3H-CNTs modified at 60 °C for 2 h exhibit the best electrocatalytic activity, showing higher redox peak current values compared to pristine carboxylated CNTs (COOH-CNTs). Sulfonic acid groups added to the surface of CNTs increase active sites for redox reactions and act as carriers for mass transfer and bridges for charge transfer, accelerating the rate of the electrode reactions. A battery consisting of SO3H-CNTs as catalysts demonstrates the outstanding charge–discharge performance at a current density of 300 mA∙cm−2. This configuration displays voltage and energy efficiencies of 81.46% and 78.83%, respectively, representing enhancements of 6.15% and 6.12% compared to that equipped with conventional graphite felts (75.31%, 72.71%). This study illustrates that taurine-functionalized carbon nanotubes serve as an efficient and promising catalyst for both the anode and cathode, leading to the improved performance of the VRFB.

ARGET-ATRP-Mediated Grafting of Bifunctional Polymers onto Silica Nanoparticles Fillers for Boosting the Performance of High-Capacity All-Solid-State Lithium-Sulfur Batteries with Polymer Solid Electrolytes.

The shuttle effect in lithium-sulfur batteries, which leads to rapid capacity decay, can be effectively suppressed by solid polymer electrolytes. However, the lithium-ion conductivity of polyethylene oxide-based solid electrolytes is relatively low, resulting in low reversible capacity and poor cycling stability of the batteries. In this study, we employed the activator generated through electron transfer atom transfer radical polymerization to graft modify the surface of silica nanoparticles with a bifunctional monomer, 2-acrylamide-2-methylpropanesulfonate, which possesses sulfonic acid groups with low dissociation energy for facilitating Li+ migration and transfer, as well as amide groups capable of forming hydrogen bonds with polyethylene oxide chains. Subsequently, the modified nanoparticles were blended with polyethylene oxide to prepare a solid polymer electrolyte with low crystallinity and high ion conductivity. The resulting electrolyte demonstrated excellent and stable electrochemical performance, with a discharge-specific capacity maintained at 875.2 mAh g-1 after 200 cycles.

Ethylene Vinyl Alcohol Copolymer Nanofibrous Cation Exchange Chromatographic Membranes with a Gradient Porous Structure for Lysozyme Separation.

Lysozyme, a common antimicrobial agent, is widely used in the food, biopharmaceutical, chemical, and medicine fields. Rapid and effective isolation of lysozymes is an everlasting topic. In this work, ethylene vinyl alcohol (EVOH) copolymer nanofibrous membranes with a gradient porous structure used for lysozyme adsorption were prepared through layer-by-layer nanofiber wet-laying and a cost-efficient ultraviolet (UV)-assisted graft-modification method, where benzophenone was used as an initiator and 2-acrylamide-2-methylpropanesulfonic acid as a modifying monomer. As indicated in the Fourier Transform Infrared (FTIR) and X-ray photoelectric energy spectrometer (XPS) investigation, sulfonic acid groups were introduced on the surface of the modified nanofibrous membrane, which possessed the ability to adsorb lysozyme. Compared with membranes with homogenous porous structures, membranes with a gradient porous structure present higher static (335 mg/g) and dynamic adsorption capacities (216.3 mg/g). Meanwhile, the adsorption capacity remained high after five cycles of the adsorption-desorption process. The results can be attributed to the gradient porous structure rather than the highest porosity and specific surface area. This suggests that the membrane with comprehensive separation performance can be designed from the view of the transmembrane porous structure, which is of significance for the development of next-generation advanced chromatographic membranes.

Efficient synthesis of benzoacridines and indenoquinolines catalyzed by acidic magnetic dendrimer

A novel solid acid catalyst with recoverability, named as Fe3O4@SiO2@TAD-G2-SO3H, was successfully synthesized by immobilizing sulfonic acid groups on triazine dendrimer-modified magnetic nanoparticles. This nanomaterial structure and composition were thoroughly characterized using various analytical techniques, including thermogravimetric analysis (TGA), elemental analysis, Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, acid–base titration, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The acid-decorated magnetic dendrimer was served as a highly effective catalyst for the synthesis of tetrahydrobenzo[c]acridin-8(9H)-one and benzo[h]indeno[1,2-b]quinoline-8-one derivatives. The reaction proceeded smoothly under mild conditions through the one-pot condensation of aromatic aldehydes, 1-naphthylamine, and either dimedone or 1,3-indanedione, affording the desired products in high yields ranging from 90 to 96%. The catalyst was easily separated from the reaction mixture by employing a magnetic field, allowing for its recycling up to five times with slight loss in its activity (only 10%). Nearly, quantitative recovery of catalyst (up to 95%) could be obtained from each run. So, this catalyst facilitates the reaction progress and simplifies the purification process. Other remarkable features of this method are operational simplicity, excellent yields, mild condition, and a wide range of substrate applicability.

Calcium complexes with sulfonic acid-containing flavonoids from the fruits of Phyllanthus acidus

Two rare flavonoid-sulfonic acids complexed with calcium ions, Ca (II)-6‑methoxy-8- sulfonic acid-naringenin complexes and Ca (II)-8-sulfonic acid-isoprunetin complexes, were isolated from the fruits of Phyllanthus acidus (L.) Skeels (Phyllanthaceae). Their planar structures were unambiguously established by extensive interpretation of the HRESIMS, 1D and 2D NMR data, and comparison to the literature data. The single crystal X-ray diffraction analysis revealed the location of sulfonic acid group on flavonoid C-8 position and the existence of metal atom in molecules, which was confirmed further to be calcium by elemental analysis. The two molecules represent the first examples of sulfonic flavonoids coordinated with calcium ions from the natural products. This example enriched the variety of natural product structures. All the isolates were evaluated for their antioxidant and anti-inflammatory activity.

"All in One" Strategy for Achieving Superprotonic Conductivity by Incorporating Strong Acids into a Robust Imidazole-Linked Covalent Organic Framework.

The fabrication of solid-state proton-conducting electrolytes possessing both high performance and long-life reusability is significant but challenging. An "all-in-one" composite, H3PO4@PyTFB-1-SO3H, including imidazole, sulfonic acid, and phosphoric acid, which are essential for proton conduction, was successfully prepared by chemical post-modification and physical loading in the rationally pre-synthesized imidazole-based nanoporous covalent organic framework (COF), PyTFB-1. The resultant H3PO4@PyTFB-1-SO3H exhibits superhigh proton conductivity with its value even highly up to 1.15 × 10-1 S cm-1 at 353 K and 98% relative humidity (RH), making it one of the highest COF-based composites reported so far under the same conditions. Experimental studies and theoretical calculations further confirmed that the imidazole and sulfonic acid groups have strong interactions with the H3PO4 molecules and the synergistic effect of these three groups dramatically improves the proton conductivity properties of H3PO4@PyTFB-1-SO3H. This work demonstrated that by aggregating multiple proton carriers into one composite, effective proton-conducting electrolyte can be feasibly achieved.

ROS-responsive sprayable hydrogel as ROS scavenger and GATA6+ macrophages trap for the prevention of postoperative abdominal adhesions

Postoperative abdominal adhesions are a common clinical problem after surgery and can cause many serious complications. Current most commonly used antiadhesion products are less effective due to their short residence time and focus primary on barrier function. Herein, we developed a sprayable hydrogel barrier (sHA-ADH/OHA-E) with self-regulated drug release based on ROS levels at the trauma site, to serve as a smart inflammatory microenvironment modulator and GATA6+ macrophages trap for non-adherent recovery from abdominal surgery. Sulfonated hyaluronic acid (HA) conjugates modified with adipic dihydrazide (sHA-ADH), and oxidized HA conjugates grafted with epigallocatechin-3-gallate (EGCG) via ROS-cleavable boronate bonds (OHA-E) were synthesized. sHA-ADH/OHA-E hydrogel was facilely fabricated within 5 s after simply mixing sHA-ADH and OHA-E through forming dynamic covalent acylhydrazones. With good biocompatibility, appropriate mechanical strength, tunable shear-thinning, self-healing, asymmetric adhesion, and reasonable in vivo retention time, sHA-ADH/OHA-E hydrogel meets the requirements of a perfect physical barrier. Intriguingly, sulfonic acid groups endowed the hydrogel with satisfactory anti-fibroblast and macrophage attachment capability, and were demonstrated for the first time to act as polyanion traps to prevent GATA6+ macrophages aggregation. Importantly, EGCG could be intelligently released by ROS triggering to alleviate oxidative stress and promote proinflammatory M1 macrophage polarize to antiinflammatory M2 phenotype. Further, the fibrinolytic system balance was restored to reduce fibrosis. Thanks to the above advantages, the sHA-ADH/OHA-E hydrogel exhibited excellent anti-adhesion effects in a rat sidewall defect–cecum abrasion model and is expected to be a promising and clinically translatable antiadhesion barrier.

Nanoscale Stabilization Mechanism of Sodium Sulfate Decahydrate at Polyelectrolyte Interfaces.

Sodium sulfate decahydrate (SSD) is a low-cost phase-change material (PCM) for thermal energy storage applications that offers substantial melting enthalpy and a suitable temperature range for near-ambient applications. However, SSD's consistent phase separation with decreased melting enthalpy over repeated thermal cycles limits its application as a PCM. Sulfonated polyelectrolytes, such as dextran sulfate sodium (DSS), have shown great effectiveness in preventing phase separation in SSD. However, there is limited understanding of the stabilization mechanism of SSD by DSS at the atomic length and time scales. In this work, we investigate SSD stabilization via DSS using neutron scattering and molecular dynamics (MD) simulations. Neutron scattering and pair distribution function analysis revealed the structural evolution of the PCM samples below and above the phase change temperatures. MD simulations revealed that water from the hydrate structure migrates from the hydrate crystal to the SSD-DSS interfacial region upon melting. The water is stabilized at this interface by aggregation around the hydrophilic sulfonic acid groups attached to the backbone of the polyelectrolyte. This architecture retains water near the dehydrated sodium sulfate, preventing phase separation and, consequently, stabilizing SSD rehydration. This work provides atomistic insight into selecting and designing stable and high-performance PCMs for heating and cooling applications in building technologies.

Thermodynamically Stable Functionalization of Microporous Aromatic Frameworks with Sulfonic Acid Groups by Inserting Methylene Spacers.

Porous aromatic frameworks (PAFs) are an auspicious class of materials that allow for the introduction of sulfonic acid groups at the aromatic core units by post-synthetic modification. This makes PAFs promising for proton-exchange materials. However, the limited thermal stability of sulfonic acid groups attached to aromatic cores prevents high-temperature applications. Here, we present a framework based on PAF-303 where the acid groups were added as methylene sulfonic acid side chains in a two-step post-synthetic route (SMPAF-303) via the intermediate chloromethylene PAF (ClMPAF-303). Elemental analysis, NMR spectroscopy, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy were used to characterize both frameworks and corroborate the successful attachment of the side chains. The resulting framework SMPAF-303 features high thermal stability and an ion-exchange capacity of about 1.7 mequiv g-1. The proton conductivity depends strongly on the adsorbed water level. It reaches from about 10-7 S cm-1 for 33% RH to about 10-1 S cm-1 for 100% RH. We attribute the strong change to a locally alternating polarity of the inner surfaces. The latter introduces bottleneck effects for the water molecule and oxonium ion diffusion at lower relative humidities, due to electrolyte clustering. When the pores are completely filled with water, these bottlenecks vanish, leading to an unhindered electrolyte diffusion through the framework, explaining the conductivity rise.

Synthesis and Characterization of Enhanced Proton-Conducting Nafion<sup>® </sup>117- Silica Composite Membranes for Fuel Cell Applications

Nafion®/silica nanocomposite membranes were prepared by impregnation method from Nafion® 117 and sol-gel pre-synthesized n-octadecyl-trimethoxy silane (C18TMS) coated silica nanoparticles. The scanning electron microscope (SEM) of pristine silica particles displayed monodispersed nanospheres with diameters ranging from 150-350 nm; while Brunauer-Emmett-Teller (BET) analysis presented 760 m2/g BET surface area, a micropore-mesopore bimodal distribution of micropore systems with respective pore volume at 14.6 Å and 17.0 Å (2.01 x 10-3 cm3/g.Å), as well as the prolific mesopores centered at 29.5 Å (5.64 x 10-2 cm3/g.Å). Characterization of Nafion® 117 based membranes on SEM, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and x-ray diffraction (XRD), and tensile stress exhibited varying surface morphology with silica loadings, structural interaction between membrane support and the ion exchanger, thermal stabilities (up to 330 °C), crystalline nature, and reasonable mechanical stability of nanocomposite membranes. The maximum water uptake (44.8 %) and proton conductivity of (1.14 x10-2 S/cm) were obtained on low Nafion®/SiO2 (5%) loaded membrane. While both composite membranes displayed the improved reduction in methanol permeability, 2.43x10-07 cm2/s at 80 °C was obtained with high Nafion®/SiO2 (10%) loading. Improved water uptake and proton conductivity substantiate the high ion exchange capacity (IEC) of 1.81 meq.g-1 when compared to IEC of 0.93 meq.g-1 [pristine Nafion®] and 1.46 meq.g-1 [Nafion®/SiO2 (10%)]. The increase in IEC value may be due to the high acid functionalization of additional sulfonic acid groups surrounded by hydrophilic segments of nanosilica, which improves the properties of the membrane. The high proton conductivity coupled with great water retention capabilities indicated that the Nafion®/SiO2 nanocomposite membranes could be utilized as proton exchange membranes for medium temperature methanol fuel cells. Keywords: Fuel cells; nanocomposite membrane; SiO2 nanofillers; methanol permeability; ion exchange capacity

Tribological Behavior of Sulfonated Polyether Ether Ketone with Three Different Chemical Structures under Water Lubrication.

With the development of the shipbuilding industry, it is necessary to improve tribological properties of polyether ether ketone (PEEK) as a water-lubricated bearing material. In this study, the sulfonated PEEK (SPEEK) with three distinct chemical structures was synthesized through direct sulfonated polymerization, and high fault tolerance and a controllable sulfonation degree ensured the batch stability. The tribological and mechanical properties of SPEEK with varying side groups (methyl and tert-butyl) and rigid segments (biphenyl) were compared after sintering in a vacuum furnace. Compared to the as-made PEEK, as the highly electronegative sulfonic acid group enhanced the hydration lubrication, the friction coefficient and wear rate of SPEEK were significantly reduced by 30% and 50% at least without affecting the mechanical properties. And lower steric hindrance and entanglement between molecular chains were proposed to be partially responsible for the lowest friction behavior of SPEEK with methyl side groups, making it a promising and competitive option for water-lubricated bearings.

Enhancing coal slime processing: Investigating the efficacy of sodium dodecyl sulfonate in the adsorption on kaolinite surfaces

AbstractAddressing the issue of processing fine kaolinite and quartz particles in coal slime, this study utilized molecular simulation and Density Functional Theory (DFT) to investigate the chelate adsorption characteristics of sodium dodecyl sulfate (SDS) on kaolinite surfaces. As a major clay mineral component in coal slime, kaolinite reduces coal's calorific value but holds potential for industrial and agricultural applications. The research identified distinct interactions between SDS and the tetrahedral SiO layer and octahedral AlO layer of kaolinite, in contrast to quartz, which contains only the tetrahedral SiO layer. This difference is crucial for the effective separation of kaolinite from quartz. The study focused on analyzing SDS adsorption on the (001) and (00‐1) planes of kaolinite. The findings revealed strong adsorption of SDS on kaolinite surfaces, especially on the (001) plane, evidenced by significant charge transfer indicating efficient chelation. This effect results from the interaction of SDS's electron‐donating atoms (such as S and O) with the metal atoms on the surface of kaolinite. Adsorption strength was quantified through adsorption energy calculations, showing a stronger interaction on the (001) surface. Experimental validations, including single mineral flotation experiments and infrared spectroscopic analysis, further corroborated the simulation outcomes. These tests demonstrated improved flotation recovery of kaolinite in the presence of SDS and with reduced particle size. Infrared analysis revealed that SDS selectively and strongly adsorbs on kaolinite surfaces, as indicated by diminished hydroxyl group stretching vibrations in the FTIR spectrum and changes in absorption peaks related to inorganic vibrations and sulfonic acid groups. The study demonstrates that SDS can selectively and effectively adsorb onto kaolinite surfaces, particularly on the (001) plane, facilitating the efficient extraction of fine kaolinite from coal slime. This research holds significant potential for enhancing the utilization of resources from coal slime in the coal industry, offering both economic and environmental benefits.

Recognizing Functional Groups of MES/APG Mixed Surfactants for Enhanced Solubilization toward Benzo[a]pyrene.

Benzo[a]pyrene is difficult to remove from soil due to its high octanol/water partition coefficient. The use of mixed surfactants can increase solubility but with the risk of secondary soil contamination, and the compounding mechanism is still unclear. This study introduced a new approach using environmentally friendly fatty acid methyl ester sulfonate (MES) and alkyl polyglucoside (APG) to solubilize benzo[a]pyrene. The best result was obtained when the ratio of MES/APG was 7:1 under 6 g/L total concentration, with an apparent solubility (Sw) of 8.58 mg/L and a molar solubilization ratio (MSR) of 1.31 for benzo[a]pyrene, which is comparable to that of Tween 80 (MSR, 0.95). The mechanism indicates that the hydroxyl groups (-OH) in APG form "O-H···OSO2-" hydrogen bonding with the sulfonic acid group (-SO3-) of MES, which reduces the electrostatic repulsion between MES molecules, thus facilitating the formation of large and stable micelles. Moreover, the strong solubilizing effect on benzo[a]pyrene should be ascribed to the low polarity of ester groups (-COOCH3) in MES. Functional groups capable of forming hydrogen bonds and having low polarity are responsible for the enhanced solubilization of benzo[a]pyrene. This understanding helps choose suitable surfactants for the remediation of PAH-contaminated soils.

Sulfonic Functionalized Polydopamine Coatings with pH-Independent Surface Charge for Optimizing Capillary Electrophoretic Separations.

Enhancing the pH-independence and controlling the magnitude of electroosmotic flow (EOF) are critical for highly efficient and reproducible capillary electrophoresis (CE) separations. Herein, we present a novel capillary modification method utilizing sulfonated periodate-induced polydopamine (SPD) coating to achieve pH-independent and highly reproducible cathodic EOF in CE. The SPD-coated capillaries were obtained through post-sulfonation treatment of periodate-induced PDA (PDA-SP) coatings adhered on the capillary inner surface. The successful immobilization of the SPD coating and the substantial grafting of sulfonic acid groups were confirmed by a series of characterization techniques. The excellent capability of PDA-SP@capillary in masking silanol groups and maintaining a highly robust EOF mobility was verified. Additionally, the parameters of sulfonation affecting the EOF mobilities were thoroughly examined. The obtained optimum SPD-coated column offered the anticipated highly pH-independent and high-strength cathodic EOF, which is essential for enhancing the CE separation performance and improving analysis efficiency. Consequently, the developed SPD-coated capillaries enabled successful high-efficiency separation of aromatic acids and nucleosides and rapid cyclodextrin-based chiral analysis of racemic drugs. Moreover, the SPD-coated columns exhibited a long lifetime and demonstrated good intra-day, inter-day, and column-to-column repeatability.

Adsorptive removal of acid blue 193 dye from wastewater using Citrullus colocynthis biomass

AbstractDue to their prevalence as contaminants in printing and textile industry wastewater, aqueous dyestuff decontamination approaches are receiving a lot of attention. Herein, the ability of powdered Citrullus colocynthis fruit peels (CCPs), a green agro-based adsorbent, to absorb an anionic acid blue 193 dye from an aqueous solution was further investigated. At pH 2.0 to 3.0, the monolayer adsorption capacity of CCP for the anionic dye species was 139.83 mg/g. Meanwhile, the successful dye uptake seen in the study is credited to the combined electrostatic interaction between the protonated adsorbent surface and the negatively charged sulfonic acid (–SO3H) group of the anionic acid blue 193 dye. Another potential adsorption mechanism is the creation of hydrogen bonds between the highly polar C = O and –OH groups of the adsorbent and the nitrogen atoms on the dye backbone. These findings suggest that CCP adsorbent is a viable candidate for the elimination of anionic acid blue 193 dyes from aqueous solution.

Adjustable n→π* electronic transition by sulfonated benzene functionalized g-C3N4 for enhanced photocatalytic H2 generation

The photocatalytic efficiency of graphitic carbon nitride (g-C3N4) in hydrogen production is primarily hindered by its poor absorption of visible light, rapid recombination of electron-hole pairs, and the absence of hydroxyl radical formation. Herein, a novel g-C3N4 nanosheets functionalized with sulfonic acid groups were effectively produced through thermal polymerization of melamine and 2, 4-diamino-6-phenyl-1, 3, 5-triazine (DPT), followed by sulfonation treatment. The introduction of the phenyl group brings about alterations to the initial symmetrical arrangement of g-C3N4, leading to the disruption of certain hydrogen bonds. This, in turn, facilitates the movement of electrons from the n to π* orbitals, resulting in enhanced light absorption and improved efficiency in charge separation. Moreover, it induces modifications to the band structure and amplifies the production of hydroxyl radicals. Additionally, the introduction of sulfonic acid enhances the water affinity and the ability of dispersing graphitic carbon nitride in water. The optimized sulfonated benzene-substituted g-C3N4 (1000-BCN-SO3H) with a melamine to DPT ratio of 4:1 exhibits a maximum hydrogen production rate of 6.52 mmol·h−1·g−1 under simulated sunlight irradiation with good cycling stability, which is 3.93 times higher than that of g-C3N4 nanosheets. This research offers a promising opportunity for a novel approach in advancing carbon nitride materials for effective photocatalytic processes.

Quantitative tailoring of water state of sulfonated corncob for boosting solar interfacial evaporation and salt resistance

Previous researches on carbon-based solar interfacial evaporation (SIE) have mainly focused on improving the solar absorption, neglecting the effect of water state on the SIE performance. This study proposes an easy strategy by combining carbonization and sulfonation using corncob as the carbon source and concentrated sulfuric acid (H2SO4) as the sulfonating agent to obtain sulfonated carbonized corncob (SCC) samples. The intermediate water to free water (IW/FW) ratio in the range of 0.53–0.96 within SCC samples has been tailored, which depends on the amount of hydrophilic sulfonic acid groups grafted on SCC. It is found that the amount of hydrophilic sulfonic acid groups and porous structure should be optimal in SCC for high IW/FW ratio. The optimized sample named as SCC-2-4.5 with a high IW/FW ratio of 0.96 and similar surface area to carbonized corncob exhibits the low enthalpy of water evaporation of 1800 J g−1, achieving the evaporation rate of 3.16 kg m−2 h−1 and evaporation efficiency of 159%. Meanwhile, SCC-2-4.5 realizes an effective separation of Na+ and Cl−, thanks to the electrostatic repulsion caused by its negatively charged sulfonic acid groups. This study provides an effective technique for regulating water state for carbon-based SIE devices on the molecular level.