Search

Electronic configurations of redox-active elements would determine the structural stability and electrochemical performance.

A kinetic study was conducted experimentally for the precipitation of ferrous oxalate. The ferrous oxalate, in the form of dihydrate (FeC2O4·2H2O), was produced by the acidic dissolution of ferrous ammonium sulfate (Fe(NH4)2(SO4)2) in an aqueous solution of oxalic acid, and then precipitated by nucleation and particle growth from supersaturated solution. The effect of the concentration of ferrous ammonium sulfate and oxalic acid as raw materials was investigated on the kinetics of the ferrous oxalate precipitation. Temperature was kept constant at 25 °C. The surface morphology, atomic compositions, and crystal phase were characterized for the ferrous oxalate precipitate collected. As the initial concentration of ferrous ammonium sulfate increased, the initial precipitation of ferrous oxalate occurred faster. The concentration of oxalic acid did not significantly affect the rate of precipitation of ferrous oxalate. The experimental behavior of ferrous oxalate precipitation was modeled with first-order models of reaction kinetics.

For the global commercialization of highly efficient and stable perovskite solar cells (PSCs), it is necessary to effectively suppress the formation of various defects acting as nonradiative recombination sources in perovskite light-harvesting materials. Interfacial defects between the charge-selective layer and the perovskite are easily formed in the solution process used to fabricate perovskite films. In addition, owing to the difference in thermal expansion coefficients between the substrate and the perovskite film, internal residual tensile stress inevitably occurs, resulting in increased nonradiative recombination. Herein, a simple compositional engineering scheme for realizing efficient and stable PSCs, which incorporates acetamidinium bromide (AABr) as an additive into the MAPbI3 lattice, is proposed. As an additive, AABr has been found to provide synergistic multiple passivation for both internal and interfacial defects. AABr was found to effectively release the tensile strain of the MAPbI3 film by forming a structure stabilized by NH–I hydrogen bonds, as evidenced by calculations based on density functional theory (DFT). Furthermore, the incorporated AABr additives created a charge carrier recombination barrier to enhance charge collection capability by reducing interfacial defects. Accordingly, a power conversion efficiency (PCE) of 20.18% was achieved using a planar device employing AABr-incorporated MAPbI3. This was substantially higher than the 18.32% PCE of a pristine MAPbI3-based device. Notably, unencapsulated PSCs using AABr-incorporated MAPbI3 absorbers exhibited excellent long-term stability, maintaining >95% of initial PCE up to 1200 hours in ambient air.

In efforts to design organic cathode materials for rechargeable batteries, a fundamental understanding of the redox properties of diverse non-carbon-based functionalities incorporated into 9,10-anthraquinone is lacking despite their potential impact. Herein, a preliminary investigation of the potential of anthraquinones with halogenated nitrogen-based functionalities reveals that the Li-triggered structural collapse observed in the early stage of discharging can be ascribed to the preference toward the strong Lewis acid-base interaction of N-Li-X (X = F or Cl) over the repulsive interaction of the electron-rich N-X bond. A further study of three solutions (i.e., substitution of NX2 with (i) BX2, (ii) NH2, and (iii) BH2) to the structural decomposition issue highlights four conclusive remarks. First, the replacement of N and/or X with electron-deficient atom(s), such as B and/or H, relieves the repulsive force on the N-X bond without the assistance of Li, and thus, no structural decomposition occurs. Second, the incorporation of BH2 is verified to be the most beneficial for improving the theoretical performance. Third, all the redox properties are better correlated with electron affinity and solvation energy than the electronegativity of functionality, implying that these key parameters cooperatively contribute to the electrochemical redox potential; additionally, solvation energy plays a crucial role in determining cathodic deactivation. Fourth, the improvement to the Li storage capability of anthraquinone using the third solution can primarily be ascribed to solvation energy remaining at a negative value even after the binding of more Li atoms than the other derivatives.

Herein, a new approach for the in situ synthesis of zeolitic imidazolate framework (ZIF) nanoparticles with triple ligands, referred to as Sogang ZIF-8 (SZIF-8), is reported for enhanced C

Despite the promise of pyrenetetrone derivatives as insoluble organic cathode compounds for lithium-ion batteries, there is limited information on their electrochemical characteristics. Herein, a highly reliable computational protocol is employed to systematically explore the redox properties and theoretical performances of pyrenetetrone derivatives. This comprehensive analysis reveals that the electrochemical redox properties of pyrenetetrone derivatives at fully charged states are determined by complementary contributions from key factors, such as dopant electronegativity, electrostatic potential of the central backbone, and interatomic electronic flow. In contrast, dopant electronegativity becomes a dominant factor for tuning the redox behaviors of these organic compounds during the Li-involved discharging process, indicating the potential of boron-doped compounds for high-performance cathodes. Further investigation highlights that the entire discharging process can be summarized as Li-induced continuous reduction in electron affinity terminated by a sudden increase in solvation energy (depending on dopant electronegativity), which emphasizes the importance of solvation energy in determining cathodic deactivation.

The effect of ultraviolet-ozone (UVO) irradiation on amorphous (am) SnO2 and its impact on the photoconversion efficiency of MAPbI3-based perovskite solar cells were investigated in detail. UVO treatment was found to increase the amount of chemisorbed oxygen on the am-SnO2 surface, reducing the surface energy and contact angle. Physicochemical changes in the am-SnO2 surface lowered the Gibbs free energy for the densification of perovskite films and facilitated the formation of homogeneous perovskite grains. In addition, the Fermi energy of the UVO-treated am-SnO2 shifted upwards to achieve an ideal band offset for MAPbI3, which was verified by theoretical calculations based on the density functional theory. We achieved a champion efficiency of 19.01 % with a statistical reproducibility of 17.01 ± 1.34 % owing to improved perovskite film densification and enhanced charge transport/extraction, which is considerably higher than the 13.78 ± 2.15 % of the counterpart. Furthermore, UVO-treated, am-SnO2-based devices showed improved stability and less hysteresis, which is encouraging for the future application of up-scaled perovskite solar cells.

The SP-HyBRID process, which has a similar performance to commercial technologies for the decontamination of a nuclear reactor coolant system, can reduce the secondary waste generation significantly. However, the process has a problem of discharging decontamination wastewater every cycle. In this study, an improved SP-HyBRID process that can conduct the process cycles continuously without discharging decontamination wastewater every cycle was designed. It was confirmed that the improved process could be effectively applied to equipment for a decontaminating test of contaminated components, and the waste reduction can be close to 15% when compared with the existing SP-HyBRID process.

Despite the potential of organic materials for cathodes in lithium-ion batteries arising from their eco-friendly production processes and structural flexibility, their redox properties are not comprehensively unveiled. In this work, the redox properties and performances for chloranil derivatives with one to four cyano functional group(s) are studied to assess their potential as high-potential organic cathode materials. The well-designed computational protocol is employed to reliably predict the redox behaviors for the organic compounds. This investigation highlights synergistic effects of carbonyls and cyanides on improving the electrochemical properties, exhibiting the remarkably high open-circuit redox potential (4.50 ​V vs. Li/Li+) and theoretical performances (515 ​mA ​h/g and 1517 ​mWh/g) for the chloranil derivative with four cyano functionalities. Furthermore, this study emphasizes that the redox potential of a chloranil derivative strongly relies not only on its structural variation but also on the Li-involved discharging process, electronic properties, and, most importantly, “solvation energy”. A universal correlation of redox potential with electron affinity and solvation energy addresses that chloranils would experience two-stage transition behaviors during the discharging process, implying a critical role of solvation energy in their cathodic deactivation and thus suggesting a smart approach for the systematic design of high-performance organic cathodes. Electrostatic potential maps unambiguously describe the change in the reductive ability of a chloranil derivative during the Li-involved discharging process.

Despite the potential of incorporating electron-withdrawing cyano functional groups in organic cathode materials for sodium-ion batteries, a systematic understanding of the effect of the functional...

Despite the importance of the atomic layer deposition (ALD) technique for developing thin films of various inorganic materials with the precisely controlled thickness, the detailed mechanistic path...

The adsorption of sulfur hexafluoride (SF6) by a transition metal-porphyrin structure embedded on the surface of graphene (MN4-graphene) was evaluated using first-principles density functional theory calculations by constructing the adsorption energy profile. The mutual balance between physisorption and chemisorption was assessed by analyzing the characteristics of the interaction between each central metal atom as an adsorption center and the SF6 molecule. CaN4- and CrN4-graphene had moderate adsorption energies of about -1.5 eV. The results indicate the feasibility of these species as reusable SF6 adsorbents, even under ambient conditions. This study provides deeper insight into the adsorption of SF6 and the potential of transition metal-porphyrin structures as SF6 capture materials for mitigating global warming.

Adsorption of CO2 molecules on amorphous silica surface in the absence/presence of Si–H defects and KCl nanoparticles under various humidity and temperature conditions is investigated using grand-c...

Limited information on organic materials for cathodes in sodium-ion batteries has been addressed as a critical issue to be overcome for designing promising candidates. Herein, we comprehensively in...

Electrochemically polymerized anthraquinone derivatives on conductive carbon nanotubes are redox-active as organic cathode materials for lithium-ion batteries. Density functional theory calculation...

Identification of redox-active moieties other than well-known carbonyl is essential to design the best candidates for organic cathodes in lithium-ion batteries among a broad-array of organic materials. In this study, an advanced computational modeling approach is employed to comprehensively investigate the redox properties for two representative organic classes, namely carbonitriles and quinones. It is highlighted that organic molecules with conjugating (non-conjugating) backbones would show higher redox potential for longer (shorter) backbone, owing to the strengthened inductive effect. Further examination verifies the importance of the relative electron-withdrawing strength of functionality over hydrogen on the redox potential and battery performance, suggesting a molecular design direction toward a carbonitrile with a longer conjugating backbone functionalized by an acyl chloride for highly-durable, high-performance cathodes. All these findings are comprehensively understood by the established universal correlations on redox property-electron affinity-solvation energy, highlighting two-stage transition behaviors of carbonitriles during the discharging process.

In this study, NaOH-assisted H

Flexible and easily-processable materials exhibiting excellent electromagnetic interference (EMI) shielding performance are desirable for EMI shielding applications in electronic devices, which are getting progressively smaller and smarter. This study reports single-walled carbon nanotube (SWCNT)/poly(ethylene-alt-maleic anhydride) (PEMA) composite films with an excellent EMI shielding performance fabricated by a simple bar-coating and doping process. The AuCl3-doped SWCNT/PEMA composite films exhibited an excellent EMI shielding effectiveness (SE) of 96.3 dB at a thickness of 0.031 mm. The EMI SE values of the AuCl3-doped SWCNT/PEMA composite films are higher than any other reported synthetic materials with a similar thickness. The excellent EMI shielding performance is attributed to the high electrical conductivity. The conductivity of the SWCNT/PEMA composite films can be increased effectively to 8500 S cm-1 through the AuCl3-doping process. It was further confirmed by MD simulations that the introduction of only 30 wt.% PEMA polymer is effective for obtaining well-dispersed SWCNTs in the composite films. It is noteworthy that such a small fraction of PEMA polymers is advantageous both for decreasing the volume fraction of the insulating polymers and facilitating the chemisorption of dopants onto the SWCNT surfaces.

A UVC photo-Fenton advanced oxidation process (AOP) was studied to develop a process for the decomposition of oxalic acid waste generated in the chemical decontamination of nuclear power plants. The oxalate decomposition behavior was investigated by using a UVC photo-Fenton reactor system with a recirculation tank. The effects of the three operational variables―UVC irradiation, H2O2 and Fenton reagent―on the oxalate decomposition behavior were experimentally studied, and the behavior of the decomposition product, CO2, was observed. UVC irradiation of oxalate resulted in vigorous CO2 bubbling, and the irradiation dose was thought to be a rate-determining variable. Based on the above results, the oxalate decomposition kinetics were investigated from the viewpoint of radical formation, propagation, and termination reactions. The proposed UVC irradiation density model, expressed by the first-order reaction of oxalate with the same amount of H2O2 consumption, satisfactorily predicted the oxalate decomposition behavior, irrespective of the circulate rate in the reactor system within the experimental range. Keywords: AOP, UVC photo-Fenton, Chemical decontamination waste, Oxalic acid

Over the past few years, metal nanowire networks have attracted attention as an alternative to transparent conducting oxide materials such as indium tin oxide for transparent conducting electrode applications. Recently, electrodeposition of metal on nanoscale template is widely used for formation of metal network. In the present work, junctionless Cu nanowire networks were simply fabricated on a substrate by forming a nanostructured Ru with 80 nm width as a seed layer, followed by direct electroless deposition of Cu. By controlling the density of Ru nanowires or the electroless deposition time, we readily achieve desired transmittance and sheet resistance values ranging from ∼1 kΩ sq−1 at 99% to 9 Ω sq−1 at 89%. After being transferred to flexible substrates, the nanowire networks exhibited no obvious increase in resistance during 8000 cycles of a bending test to a radius of 2.5 mm. The durability was verified by evaluation of its heating performance. The maximum temperature was greater than 180 °C at 3 V and remained constant after three repeated cycles and for 10 min. Transmission electron microscopy and x-ray diffraction studies revealed that the adhesion between the electrolessly deposited Cu and the seed Ru nanowires strongly influenced the durability of the core–shell structured nanowire-based heaters.