A sub-10 μm Ion Conducting Membrane with an Ultralow Area Resistance for a High-Power Density Vanadium Flow Battery

With the outstanding features of high safety, high efficiency, and long lifespan, the vanadium flow battery (VFB) is well-suited for large-scale energy storage; however, it suffers from low power density. The high ion conductivity of membranes is very important to increase the performance of VFBs at high current densities and improve their power density. Here, we show a highly conductive free-standing sub-10 μm polybenzimidazole (PBI) membrane. The decrease in the membrane thickness contributes to shorter ion-transport pathways and lower resistance. The relatively loose cross-linked structure of the thin membrane provides sufficient free volume for ion transport. According to these results, the membrane exhibits an ultralow area resistance of 0.04 Ω cm2, much lower than that of commercial Nafion 115 membrane (0.20 Ω cm2), making the ion conductivity superior. Additionally, the sub-10 μm PBI membrane also shows a very high tensile strength of 45.5 MPa and high ion selectivity. The VFB assembled with a sub-10 μm PBI membrane delivers a high energy efficiency of approximately 80% at a high current density of 200 mA cm–2 and can run stably for more than 500 cycles without obvious performance decay. The increased performance of the VFB at a very high current density of 200 mA cm–2 contributes to its higher power density. Therefore, it is an available way to adopt free-standing sub-10 μm PBI membranes with high conductivity, selectivity, and mechanical stability to improve the power density of VFBs. Similarly, the application of it will also accelerate the practical application of VFB energy storage technology

Cotton <i>GhMKK1</i> Induces the Tolerance of Salt and Drought Stress, and Mediates Defence Responses to Pathogen Infection in Transgenic <i>Nicotiana benthamiana</i>

<div><p>Mitogen-activated protein kinase kinases (MAPKK) mediate a variety of stress responses in plants. So far little is known on the functional role of MAPKKs in cotton. In the present study, <i>Gossypium hirsutum MKK1</i> (<i>GhMKK1</i>) function was investigated. GhMKK1 protein may activate its specific targets in both the nucleus and cytoplasm. Treatments with salt, drought, and H₂O₂ induced the expression of <i>GhMKK1</i> and increased the activity of <i>GhMKK1</i>, while overexpression of <i>GhMKK1</i> in <i>Nicotiana benthamiana</i> enhanced its tolerance to salt and drought stresses as determined by many physiological data. Additionally, <i>GhMKK1</i> activity was found to up-regulate pathogen-associated biotic stress, and overexpression of <i>GhMKK1</i> increased the susceptibility of the transgenic plants to the pathogen <i>Ralstonia solanacearum</i> by reducing the expression of <i>PR</i> genes. Moreover, <i>GhMKK1</i>-overexpressing plants also exhibited an enhanced reactive oxygen species scavenging capability and markedly elevated activities of several antioxidant enzymes. These results indicate that <i>GhMKK1</i> is involved in plants defence responses and provide new data to further analyze the function of plant MAPK pathways.</p></div

Expression patterns of <i>GhMKK1</i> in different tissues, developmental stages and under different stress conditions.

<p>(A) The tissue-specific expression of <i>GhMKK1</i> was analysed via RT-PCR using total RNA extracted from the roots, stems, and cotyledon leaves of 7-day-old cotton seedlings. (B) The expression profiles of <i>GhMKK1</i> were measured in the cotyledon leaves of 7-day-old cotton seedlings. For the stress treatments, 7-day-old cotton seedlings were obtained from a hydroponic culture and were subjected to treatment with 100 mM NaCl (C), 15% PEG (D), wounding (E), 100 µM H₂O₂ (F), low temperature (4°C) (G), 2 mM SA (H), 100 µM ABA (I), 100 µM MeJA (J), 100 µM ET (K), release from ethephon, and <i>R. solanacearum</i> infection (L). Total RNA was isolated at the indicated times following the initiation of treatments and was subjected to RT-PCR analysis. The obtained PCR products were visualized via agarose gel electrophoresis, followed by ethidium bromide staining. The <i>18S rRNA</i> gene was employed as an internal control. This experiment was repeated at least twice.</p

Schematic experimental system for photo degradation experiments.

<p>Schematic experimental system for photo degradation experiments.</p

The lengths of the exons and introns in <i>GhMKK1</i> and <i>AtMKK1</i>.

<p>The lengths of the exons and introns in <i>GhMKK1</i> and <i>AtMKK1</i>.</p

Salt tolerance test comparing the wild-type and <i>GhMKK1</i>-overexpressing <i>N. benthamiana</i> plants.

<p>(A) Analysis of <i>GhMKK1</i> expression in wild-type (WT) and T₁ OE plants. (B) Seed germination on MS medium containing different concentrations of NaCl. (C–D) Germination rates of the WT and OE lines under normal and NaCl treatment conditions. Based on daily scoring, the results obtained using MS medium containing 200 mM NaCl are presented. The presented data are the means ±SE of three independent experiments (<i>n</i> = 3). Asterisks (* or **) above the lines indicate significant differences (*<i>P</i><0.05; **<i>P</i><0.01) according to Duncan's multiple range test performed in SAS version 9.1 software. (E) Post-germination seedling development of the WT and the OE lines on MS supplemented with different concentrations of NaCl. The seeds sown on MS medium that showed radicle emergence after 3 d were transferred to MS medium containing different concentrations of NaCl. The plates were oriented vertically, with seedlings kept upside down, and a photograph was taken 14 d after transfer. (F) Primary root lengths of the seedlings 14 d after germination in the presence of different NaCl concentrations. The presented data are the means ±SE of three independent experiments (<i>n</i> = 6). Different letters above the columns indicate significant differences (<i>P</i><0.05) according to Duncan's multiple range test performed using SAS version 9.1 software. (G) Photograph of representative 10-week-old WT and OE plants grown in soil containing 200 mM NaCl for 14 d. (H) Survival rates of 10-week-old plants treated with 200 mM NaCl for 14 d. The presented data are the means ±SE of three independent experiments (<i>n</i> = 6). Different letters above the columns indicate significant differences (<i>P</i><0.01) according to Duncan's multiple range test performed using SAS version 9.1 software.</p

Drought tolerance test comparing the wild-type and the <i>GhMKK1</i>-overexpressing <i>N. benthamiana</i> plants.

<p>(A) Seed germination on MS medium with 0, 50, 100, or 200 mM mannitol. (B–C) Germination rates of the WT and OE lines under normal and mannitol treatment conditions. Based on daily scoring, the results obtained on the MS medium containing 200 mM mannitol are presented. The presented data are the means ±SE of three independent experiments (<i>n</i> = 3). Asterisks (* or **) above the lines indicate (highly) significant differences (*<i>P</i><0.05; **<i>P</i><0.01) according to Duncan's multiple range test performed using SAS version 9.1 software. (D) Photograph of representative 10-week-old WT and OE plants grown in soil under drought conditions for 10 d, then watered for 2 d to allow them to recover. BD, before drought treatment; RW, rewatering. (E) The water loss from the detached leaves of WT and OE plants at the indicated times. The rate of water loss was calculated by the loss of fresh weight in the samples. The presented data are the means ±SE of three independent experiments (<i>n</i> = 6). Asterisks (**) above the lines indicate (highly) significant differences (<i>P</i><0.01) according to Duncan's multiple range test performed using SAS version 9.1 software. (F) Survival rates of WT and OE plants under drought stress. The presented data are the means ±SE of three independent experiments (<i>n</i>≥50). Different letters above the columns indicate significant differences (<i>P</i><0.0001) according to Duncan's multiple range test performed using SAS version 9.1 software. (G–I) Phenotype of roots subjected to drought stress for WT and OE plants, together with additional root lengths and fresh weights. The presented data are the means ±SE of three independent experiments (<i>n</i> = 6). Different letters above the columns indicate significant differences (<i>P</i><0.0001) according to Duncan's multiple range test performed using SAS version 9.1 software. (J–K) Stomatal changes observed with a microscope before and after drought treatment. The stomatal aperture is displayed. BD, before drought treatment; RW, rewatering. Bar  = 200 µm. The presented data are the means ±SE of three independent experiments (<i>n</i> = 6). Different letters above the columns indicate significant differences (<i>P</i><0.01) according to Duncan's multiple range test performed using SAS version 9.1 software.</p

Comparation of photocatalytic rate constants (k) of PCP with different photocatalyst conditions under 3 kinds of UV irradiation.

<p>Comparation of photocatalytic rate constants (k) of PCP with different photocatalyst conditions under 3 kinds of UV irradiation.</p

Analysis of ROS accumulation in WT and OE plants in response to abiotic stresses.

<p>(A–B) Abiotic stress-induced H₂O₂ and O₂⁻ accumulation detected via DAB staining and NBT staining, respectively. (C) Leaf disks from WT and OE plants were incubated in different concentrations of MV (0, 200, or 400 µM) under greenhouse conditions. (D) Relative chlorophyll contents were determined in the leaf disks of WT and OE plants following MV treatments. Disks floated in water were used as a control. The presented data are the means ±SE of three independent experiments (<i>n</i> = 6). Different letters above the columns indicate significant differences (<i>P</i><0.0001) according to Duncan's multiple range test performed using SAS version 9.1 software.</p

Photocatalytic degradation of PCP with TiO₂, graphene-TiO₂ and without catalyst under different pH values: (a) pH = 1; (b) pH = 4; (c) pH = 10; (d) pH = 13.

<p>Photocatalytic degradation of PCP with TiO₂, graphene-TiO₂ and without catalyst under different pH values: (a) pH = 1; (b) pH = 4; (c) pH = 10; (d) pH = 13.</p