Interfacial interactions between halides of the perovskite precursors and the oxygen groups of GO reduce GO, and determine perovskite yield.

used with dimethylformamide (DMF), dimethylsulfoxide (DMSO), or gamma butyrolactone. [1b,3,4] The precursor film is then converted to the perovskite structure by annealing on a hot plate at 60-200 °C. The high temperature treatment however spoils the film properties by generating intrinsic defects, stoichiometric or compositional changes, rapid film degradation, uncontrollable perovskite precipitation, inhomogeneous perovskite crystallization at the perovskite/underlayer interface, and incomplete surface coverage with a random film texture. [5] To avoid high temperature annealing processes, solution-based methods have been developed. However, in those studies, the perovskite colloidal particles are synthesized in solution and then deposited on the underlayer film without elimination of annealing. [6][7][8] They are enabled by the addition of small molecules, use of an excess organic component, or treatment with hypophosphorous acid. Therefore, these solution reactions still require high temperature and thus cannot avoid unmanageable surface reactions resulting in nonstoichiometric dopants and phase segregation. [9] In order to lower the reaction temperature, acid-treated methods including acidcatalyzed techniques [10] and acid-base solutions [11] have been developed particularly for mixed [12,13] and single halides [14] in DMF. [15][16][17][18][19] The acid-catalyzed reactions are, in general, initiated by the formation of solvated PbI 4 2− anions that further react with CH 3 NH 3 + cations for CH 3 NH 3 PbI 3 (s) (MAPbI 3 ) Methylammonium lead iodide (MAPbI 3 ) perovskites are organic-inorganic semiconductors with long carrier diffusion lengths serving as the light-harvesting component in optoelectronics.Through a substitutional growth of MAPbI 3 catalyzed by polar protic alcohols, evidence is shown for their substrate-and annealing-free production and use of toxic solvents and high temperature is prevented. The resulting variable-sized crystals (≈100 nm-10 µm) are found to be tetragonally single-phased in alcohols and precipitated as powders that are metallic-lead-free. A comparatively low MAPbI 3 yield in toluene supports the role of alcohol polarity and the type of solvent (protic vs aprotic). The theoretical calculations suggest that overall Gibbs free energy in alcohols is lowered due to their catalytic impact. Based on this alcohol-catalyzed approach, MAPbI 3 is obtained, which is chemically stable in air up to ≈1.5 months and thermally stable (≤300 °C). This method is amendable to large-scale manufacturing and ultimately can lead to energy-efficient, low-cost, and stable devices.

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Since carbon tetrahalides CX 4 (X = Cl/Br) are adsorbed on carbon nanotubes and graphene sheets, we have studied the structures, adsorption energies, and electronic properties of CX 4 adsorbed on benzene, coronene, and graphene using dispersion corrected density functional theory (DFT) with hybrid functionals. As compared with the benzene−CX 4 complexes (with binding energy of ∼14/15 kJ/mol) where electrostatic energy is significant due to the halogen bonding effect, the graphene−CX 4 complexes show about three times the benzene−CX 4 binding energy (∼40/45 kJ/mol) where the dispersion interaction is overwhelming with insignificant electrostatic energy. Since the X atoms in CX 4 are slightly positively charged and the X atom's ends are particularly more positively charged due to the σ-hole effect, CX 4 behaves as an electron acceptor. This results in electron transfer from locally negatively charged C sites of benzene/coronene to CX 4 . In contrast, no electron transfer occurs from graphene to CX 4 because of the large work function of graphene and significant electron affinity of CX 4 and because homogeneously charge-neutral graphene has no locally charged sites. Nevertheless, due to the symmetry breaking upon adsorption, the CX 4adsorbed graphene shows a small band gap opening without p-doping. On the other hand, CF 4 behaves as an electron donor due to the negatively charged F atoms, which results in electron transfer from CF 4 to the locally negatively charged C sites of benzene/coronene. Again, no electron transfer occurs from CF 4 to graphene because of high ionization energy of CF 4 , and so the CF 4 -adsorbed graphene opens only a small band gap without n-doping.

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CeOx hybrid nanoparticles were synthesized and evaluated for use as radical scavengers, in place of commercially available Ce(NO3)3 and CeO2 nanoparticles, to avoid deterioration of the initial electrochemical performance and/or spontaneous aggregation/precipitation issues encountered in polymer electrolyte membranes. When CeOx hybrid nanoparticles were used for membrane formation, the resulting membranes exhibited improved proton conductivity (improvement level = 2–15% at 30–90 °C), and thereby electrochemical single cell performance, because the –OH groups on the hybrid nanoparticles acted as proton conductors. In spite of a small amount (i.e., 1.7 mg/cm3) of introduction, their antioxidant effect was sufficient enough to alleviate the radical-induced decomposition of perfluorinated sulfonic acid ionomer under a Fenton test condition and to extend the chemical durability of the resulting reinforced membranes under fuel cell operating conditions.

Water resource pollution by nitrate-nitrogen, mainly caused by anthropogenic causes, induces eutrophication of water resources, and indicates the degree of organic pollution. Therefore, this study devised a method for coating PFSA ionomer with excellent chemical resistance without disassembling the module to improve the removal rate of nitrate-nitrogen in water by using a cyclic coating method on a commercially available nanofiltration membrane (NF membrane) module. Nafion was prepared as a supercritical fluid dispersion using a high-temperature and high-pressure reactor, and the particle size and the degree of dispersion of the dispersion were analyzed by DLS. The crystallinity was confirmed through XRD by drying the dispersion in the liquid state. After the dispersion was prepared as a membrane according to the heat treatment conditions, the characteristics according to the particle size were analyzed by tensile strength and TEM. The nitrate-nitrogen removal rate of the NF membrane module coated with the dispersion was increased by 93% compared to that before coating. Therefore, the result showed that the cycle coating method devised in this study could efficiently coat the already commercialized module and improve performance.