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[en] Zn2+, Cu2+, and Ni2+ ionic permeabilities through a Nafion 115 membrane, containing sulfonate functional groups capable of cation exchange with metal ions, were measured in this work. Single and binary salt mixtures were prepared at 10, 100, and 1000 ppm concentrations, and the ionic permeabilities and selectivities (α) were measured. The ionic permeabilities were in the 10−6–10−5 cm2/s range, and the order of ion permeability depends on the ionic concentration. At low (10 ppm) concentration, the smaller Ni2+ transported faster than the other two ions and the permeability was dominated by the ionic diffusivity. As the concentration was increased to 100 and 1000 ppm, the ion permeability was increased because more ions were exchanged onto the sulfonate groups. Moreover, Zn2+ became the fastest ion among the three as the ion transport became solubility-controlled at the medium and high concentrations. In spite of the ion permeability order being dependent upon the feed concentration, the separation selectivity was not affected by the presence of co-ions in the tested conditions. The separation selectivity from a binary mixture could be estimated from the permeability ratio obtained from single solutions.
[en] Highlights: • Preparation of chitosan nanoparticles from bulk to enhance the degree of deacetylation. • The incorporation of chitosan nanoparticles into a QPVA matrix to form a nanocomposite membrane. • The nanocomposite constructed into thin-film membranes using the solution casting method. • To improve permeability, glutaraldehyde was cross-linked with the nanocomposite membranes. • A direct methanol alkaline fuel cell was studied at different temperatures. - Abstract: In this study, we designed a method for the preparation of chitosan nanoparticles incorporated into a quaternized poly(vinyl alcohol) (QPVA) matrix for direct methanol alkaline fuel cells (DMAFCs). The structural and morphological properties of the prepared nanocomposites were studied using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and dynamic laser-light scattering (DLS). The crystallinity of the nanocomposite solid electrolytes containing 0 and 10% chitosan nanoparticles were investigated using differential scanning calorimetry (DSC). The electrochemical measurement of resulting nanocomposite membranes were analyzed according to the following parameters: methanol permeability, liquid uptakes, ionic conductivity and cell performances. The composite membranes with 10% chitosan nanoparticles in a QPVA matrix (CQPVA) show suppressed methanol permeability and higher ionic conductivity than pristine QPVA. In addition, the glutaraldehyde cross-linked nanocomposite film exhibited improvement on the methanol barrier property at 80 °C. The peak power density of the DMAFCs reached 67 mW cm−2 when fed into 1 M of methanol in 6 M of KOH.
[en] The objectives of this work are to prepare and characterize poly[2,2′-m-(phenylene)-5,5′-bibenzimidazole]/graphene oxide (PBI/GO) solid electrolyte for direct alcohol alkaline fuel cell (DAAFC) applications. GO nanosheets are coated onto a PBI surface using a spin coater to construct the PBI/GO composite membrane. The PBI/GO composite membrane exhibits an ionic conductivity of 2.53 × 10−2 S cm−1 at 80 °C, which is improved by 72–93% when compared with the pure PBI membrane. In addition, the methanol permeability is reduced by 18–25% by incorporating GO onto the PBI top surface. The peak power density (Pmax) of the PBI/GO electrolyte reaches 200 mW cm−2 when using alkaline methanol as fuel with Pt-based catalysts, or 120 mW cm−2 when fed with an ethanol and alkaline solution mixture at 80 °C. Replacing the Pt-based catalysts with Hypermec™ catalysts resulted in Pmax of 40 and 100 mW cm−2, for methanol and ethanol fuel cells, respectively. These superior DAAFC power outputs are ascribed to the improved anion conduction of the KOH doped GO and the suppressed methanol cross-over from high aspect ratio GO as the alcohol barrier layer. - Highlights: • Spin-coating technique are used to construct PBI/GO composite membrane. • Pmax of DMAFC and DEAFC obtained at 200 and 120 mW cm−2 using Pt-based electrocatalyst. • Pt-based electrocatalyst is favored for DMAFCs whereas non-Pt is favored for DEAFCs. • PBI/GO composite membrane produce higher power densities compared with literature data's.
[en] Graphical abstract: Schematic diagram for Li-rich oxide (Li_1_._2Ni_0_._2Mn_0_._6_0O_2) coated with Li_0_._7_5La_0_._4_2TiO_3 (LLTO) solid ionic conductor. - Highlights: • Li_1_._2Ni_0_._2Mn_0_._6_0O_2/C composite material was prepared by one-pot solid-state method. • 1D a-MnO_2 nanowires and microsphere hollow b-Ni(OH)_2 were prepared by a hydrothermal method. • 1 wt.%LLTO-coated composite showed the best performance among samples. • LLTO layer not only improves the ionic transport of Li-rich oxide material, but also prevent Li-rich material corrosion. - Abstract: Li-rich (spray-dried (SP)-Li_1_._2Ni_0_._2Mn_0_._6_0O_2) composite materials were prepared via two-step ball-mill and spray dry methods by using LiOH, α-MnO_2, β-Ni(OH)_2 raw materials. Two raw materials of α-MnO_2 nanowires and microsphere β-Ni(OH)_2 were synthesized by a hydrothermal process. In addition, Li_0_._7_5La_0_._4_2TiO3 (LLTO) fast ionic conductor was coated on SP-Li_1_._2Ni_0_._2Mn_0_._6_0O_2 composite via a sol–gel method. The properties of the LLTO-coated SP-Li_1_._2Ni_0_._2Mn_0_._6_0O_2 composites were determined by X-ray diffraction, scanning electron microscopy, micro-Raman, XPS, and the AC impedance method. The discharge capacities of 1 wt.%-LLTO-coated SP-Li_1_._2Ni_0_._2Mn_0_._6_0O_2 composites were 256, 250, 231, 200, 158, and 114 mAh g"_−"_1 at rates of 0.1, 0.2, 0.5, 1, 3, and 5C, respectively, in the voltage range 2.0–4.8 V. The 1 wt.%-LLTO-coated Li-rich oxide composite showed the discharge capacities of up to 256 mAh g"−"1 in the first cycle at 0.1C. After 30 cycles, the discharge capacity of 244 mAh g"−"1 was obtained, which showed the capacity retention of 95.4%.
[en] Highlights: • The LiFePO4/porous graphene oxide/C was prepared by a hydrothermal method and a spray dry process. • The porous graphene oxide was prepared through an activation method. • The discharge capacity of the SP-LFP/1%PGO/C is 107 mAh g−1 after 1000 cycles at 10C rate. • The SP-LFP/PGO/C material shows promising candidate for high-power Li-ion battery in EV. - Abstract: A 3D spray-dried micro/mesoporous LiFePO4/porous graphene oxide/C (denoted as SP-LFP/PGO/C) composite material is synthesized via a three-step process, i.e., hydrothermal process, carbon coating, and spray dry method in sequence. The 2D porous graphene oxide (denoted as PGO) material is first prepared through an activation method. The galvanostatic charge-discharge measurements of LFP composites without graphene oxide, with 1 wt% graphene oxide, and 1 wt% PGO are conducted in the potential range of 2–3.8 V at various rates (0.1–10C). It is revealed that the SP-LFP/PGO/C material shows the best performance among three samples. The discharge capacities of the SP-LFP/PGO/C composites are observed to 160, 152, 151, 149, 144, 139, 127 mAh g−1 at 0.1C, 0.2C, 0.5C, 1C, 3C, 5C and 10C rate. In particular, the discharge capacity of the SP-LFP/PGO/C composite with 1 wt% PGO is 107 mAh g−1 after 1000 cycles at a 10C rate, and its capacity retention is ca. 97%. It is due to the unique structural and geometrical feature of SP-LFP/PGO/C composite, there the diamond-like (rhombus) LFP nanoparticles are embedded in porous GO matrix which forming a porous three-dimensional network for fast electronic and ionic transport channels.