ACS Omega最新文献

In this study, bacterial cellulose-polyelectrolyte complex (BC/PEC) composite hydrogels were prepared for an electrode separator. First, the poly(sodium 4-styrenesulfonate)/poly(dimethyl diallyl ammonium chloride) hydrogel was prepared using NaCl as a shielding agent and a dialysis tube to control the formation of the PEC hydrogel. BC was incorporated into the supporting skeleton. The 3D BC sponge was prepared by using an alkali swollen BC gel, followed by freeze–thaw cycles to develop the porous framework. The BC backbone was then cross-linked with glutaraldehyde (GA) under acidic conditions to obtain cross-linked BC (BC-GA), resulting in the improved dimensional stability of the BC skeleton in an alkali medium. Subsequently, the PEC was introduced into the BC-GA pores, resulting in the BC-GA/PEC composite hydrogel with improved mechanical and dimensional properties and thermal stability. Electrolyte permeability tests with 6 M KOH showed that BC/PEC had lower permeability (approximately 2 × 10^–2 cm²/min) compared to BC and BC-GA (1.0–1.5 × 10^–1 cm²/min) compared to the ionic conductivity of BC-GA/PEC with values of 30.9–55.9 mS/cm. The charge–discharge cycling performance of BC-GA/PEC hydrogels as a zinc battery separator was evaluated using plating/stripping tests, revealing that the zinc anode surface exhibited less corrosion and slower dendrite growth. This phenomenon was due to the decrease in Zn²⁺ crossover by either repulsion or attraction forces between Zn²⁺ and BC-GA/PEC hydrogels, making them an alternative for electrode separators in place of liquid electrolyte separators.

[This retracts the article DOI: 10.1021/acsomega.0c05826.].

Ultralow decoration of platinum nanoparticles (Pt NPs) (0.32 wt %) onto carbon spheres (CS) has been developed for hybrid formation, using hydrothermal heat treatment, followed by chemical reduction of nanoparticles. The successful decoration of CSs bearing amine groups with platinum nanoparticles was confirmed directly by X-ray photoelectron spectroscopy. The uniform distribution and crystallinity of the Pt NPs in the hybrid structures were confirmed from X-ray diffraction spectroscopy and transmission electron microscopy. The hydrogen evolution reaction studied on the proposed Pt-CS hybrids reveals an onset potential of only -144 mV (vs RHE, reversible hydrogen electrode) with a current density of 10 mA/cm² under an acidic 0.5 M H₂SO₄ medium, which exhibits a better performance as compared to a similar Pt-carbon hybrid catalyst reported in the literature. The Pt-CS hybrid stability assessments revealed a minimal overpotential loss (9 mV) from 144 to 153 mV after 200 cycles. Such hybrids have possible applications in environmental water purification and renewable energy production.

In this work, surface-enhanced Raman scattering substrates with triangular silver nanoprisms (AgNPrs) dropped on copper hydroxide nanowires (CuOHNWs) were evaluated. AgNPrs were synthesized in colloidal solution using Ag nitrate, polyvinylpyrrolidone, trisodium citrate dihydrate, hydrogen peroxide, and sodium borohydride (NaBH₄). A set of five solutions with volume percentages from 0.99 to 4.76% v/v of NaBH₄ as reducing agents was studied. The reaction time associated with blue coloration was determined. The evolution of the colloids was studied by UV–vis spectroscopy over a period of 42 days, confirming the good stability of AgNPrs. In addition, their colloidal stability was also verified by the zeta potential. The influence of NaBH₄ concentration over the AgNPrs morphology was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Finally, SERS substrates were fabricated with AgNPrs deposited on CuOHNW and used to detect methylene blue as a probe molecule. AgNPrs obtained with 2.91% v/v NaBH₄ presented the smallest sizes, and their SERS substrate presented the best Raman intensity.

Strontium titanate (STO), a cubic perovskite material, has gained recent attention as a supercapacitor active material with its pseudocapacitive energy storage attributed to anion intercalation. However, very few in-depth studies have been conducted to understand the anion storage properties of STO and its metal-doped derivative compounds. In this study, we explored the anion-insertion storage mechanism of Mn-doped strontium titanate (Mn-STO) compared to pristine STO. The polycrystalline Mn-STO, synthesized via solid-state reaction, showed 3-fold times higher electrochemical surface area and exhibited enhanced anion storage compared to pristine STO. Detailed anion kinetics and diffusion studies reveal that the anion storage in Mn-STO is dominated by the bulk diffusion-controlled pseudocapacitive process than in STO. Further, the supercapacitor fabricated with Mn-STO in a 3 M KOH aqueous electrolyte with 0.1 M MnSO₄ additives demonstrated excellent cycling stability, retaining 100% capacitance after 10,000 cycles, highlighting the potential of Mn-STO as an electrode material for supercapacitor applications.

In this study, we showed that hybrid reinforcement-a combination of nanoparticles and fibers-can provide more effective reinforcement for increasing the recovery stress of a shape memory polymer (SMP) than using either filler individually. We mixed carbon fibers (CF) and carbon nanotubes (CNT) into a poly(lactic acid) (PLA) matrix on a twin-screw extruder and injection molded specimen from the hybrid composite. Subsequently, some of the specimens were subjected to crystallizing heat treatment, while others were kept as molded to study the effects of crystallinity as well. We investigated the properties of the specimens with scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and mechanical and thermomechanical tests. We found that the CF helped disperse the CNT properly, allowing them to reinforce more effectively. The CF increased the recovery stress of the samples significantly while decreasing the precision of the recovery due to the rigid nature of the reinforcement. Dispersed CNT could further increase the recovery stress without impairing precision because dispersed CNT formed a deformable reinforcing structure that did not increase elongation at break or plastic strain.

Strontium titanate (STO), a cubic perovskite material, has gained recent attention as a supercapacitor active material with its pseudocapacitive energy storage attributed to anion intercalation. However, very few in-depth studies have been conducted to understand the anion storage properties of STO and its metal-doped derivative compounds. In this study, we explored the anion-insertion storage mechanism of Mn-doped strontium titanate (Mn-STO) compared to pristine STO. The polycrystalline Mn-STO, synthesized via solid-state reaction, showed 3-fold times higher electrochemical surface area and exhibited enhanced anion storage compared to pristine STO. Detailed anion kinetics and diffusion studies reveal that the anion storage in Mn-STO is dominated by the bulk diffusion-controlled pseudocapacitive process than in STO. Further, the supercapacitor fabricated with Mn-STO in a 3 M KOH aqueous electrolyte with 0.1 M MnSO₄ additives demonstrated excellent cycling stability, retaining 100% capacitance after 10,000 cycles, highlighting the potential of Mn-STO as an electrode material for supercapacitor applications.

Aromatic azo compounds stand as a highly sought-after class of substances owing to their extensive array of applications across various fields. Despite their significance, their synthesis often presents challenges, requiring either multistep reactions or being restricted to specific substrate types. In this study, we are showing the universality and mechanistic aspects of a one-step approach for synthesis of nonsymmetrical azoarenes via the Buchwald–Hartwig amination reaction of (pseudo)haloaromatics with arylhydrazines, conducted in the presence of atmospheric oxygen. This reaction protocol yields products in up to 85% yield and is compatible with a wide class of substituents, making it highly adaptable. Notably, the inclusion of BINAP as a ligand plays a pivotal role in achieving favorable outcomes. This study not only offers a versatile solution to a long-standing synthetic challenge but also provides experimental and computational insights into the mechanisms driving the reaction.

Lithium-rich layered oxide materials (Li-NMC) are considered a potential cathode material for next-generation batteries, thanks to their high theoretical specific capacity. Large potential drop and capacity loss after long cycles are the main obstacles to expanding commercial utilization of Li-NMC. In the past decade, great efforts have been made to overcome those issues of Li-NMCs. In this study, Al-doped Li_1.20Mn_0.52-x Al _x Ni_0.20Co_0.08O₂ cathode materials are for the first time synthesized by a supercritical-CO₂-assisted method. Upon the electrochemical tests of Al-doped Li-rich NMCs, the optimal initial charge/discharge profile is obtained for the Li-NMC-Al02 cathode with 374.6/247.5 mAh/g compared with that of 320.7/235.1 mAh/g for the pristine Li-NMC-Al00 sample at the C/20 rate. In addition, the Li-NMC-Al02 cathode shows an enhanced rate-capability performance compared to the pristine sample at relatively low rates. When the current density is increased from C/10 to 3C, the charge/discharge capacity values of the Li-NMC-Al02 cathode are measured as 249.88/105.84 mAh/g. Last but not least, Li-NMC-Al02 demonstrates an excellent energy retention of 92.32%, which is notably higher than that of pristine Li-NMC-Al00 (86.4%) after 120 cycles at the C/20 rate. Overall, the present fabrication and doping strategy opens a new avenue for commercialization of Li-NMC cathode materials.

A novel and straightforward approach was employed to augment the dielectric constant and diminish the elastic modulus of polyurethane (PU) through the integration of modified silica (NSiO₂) into the matrix. The incorporation of NSiO₂ resulted in the disruption of N-H/C=O hydrogen bonds between the PU chains, which subsequently led to an enhancement in the polarizability of the chains and an increase in the dielectric constant of PU. Concurrently, the addition of NSiO₂ resulted in a reduction of the elastic modulus (Y) of PU, which was attributed to the disruption of the hard domains of PU. The concurrent increase in the dielectric constant and reduction in Y give rise to a 60% enhancement in electromechanical sensitivity at 10³ Hz. Furthermore, PU/NSiO₂ displays robust electrical breakdown strength due to the insulation properties of SiO₂. At a NSiO₂ content of 3%, the breakdown strength of PU/NSiO₂-3 increases to 145.12 MV/m, which is 1.6 times that of PU (91.03 MV/m). This study presents a novel approach to the design and preparation of PU with a high dielectric constant and enhanced electrical breakdown strength.