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In this study, polymer-coated anisotropic inorganic nanowires dispersed in PBI matrix were introduced to construct 1D proton conducting channels within PBI. Ionic-liquid and solvothermal methods were used for the synthesis of ZrO2 and W18O49 NWs, which were coated with PVPA and PDDA polymers to increase their proton conductivity. Our results showed that, prepared membranes have amorphous nature due to the dominating presence of PBI. SEM analysis revealed the average thickness of membrane of about 36 µm. TG/DTA analysis detected lower weight loss of W18O49 NWs (total 2.8%) compared to ZrO2 NWs (18%). Proton conductivity analysis showed that, PDDA/W18O49 NWs possess relatively 4 times higher proton conductivity (4 × 10−4 Scm−1) compared to PDDA/ZrO2 NWs (1 × 10−4 Scm−1) at 80 ℃. In addition, PDDA-coated W18O49 NWs dispersed PBI membranes showed the highest fuel cell current density (1.2 A/cm2) and power density (215 mW/cm2) at 150 ℃ after 24 h which is nearly 2.5 times higher than pure PBI membrane. In addition, they exhibited the lowest in-situ proton resistance of about (0.47 Ω) compared with that of pure PBI membrane (0.8 Ω). Our results are introducing new concepts towards the development of thin and efficient polymer electrolyte membranes for PEM fuel cells. [ABSTRACT FROM AUTHOR]

Anodic TiO2 nanotube arrays (TNTAs) have attracted much attention due to their excellent photoelectrochemical (PEC) properties. In this work, the tube length of TNTAs was optimized for efficient PEC water splitting under two different conditions, in which very few or a massive amount of gas bubbles were generated on the electrodes. As a result, relatively longer TNTAs were found to be preferable for higher PEC performance when a larger number of bubbles were generated. This suggests that the mass transport in the electrolyte is assisted by the generated bubbles, so that the electrode surfaces are more easily exposed to the fresh electrolyte, leading to the higher PEC performance. [ABSTRACT FROM AUTHOR]

In this study, nanoporous anodic film was produced by anodization of niobium, Nb in a fluoride ethylene glycol electrolyte. The effect of anodization voltage and electrolyte temperature was studied to find an optimum condition for circular, ordered, and uniform pore formation. The diameter of the pores was found to be larger when the applied voltage was increased from 20 to 80 V. The as-anodized porous film was also observed to comprise of nanocrystallites which formed due to high field-induced crystallization. The nanocrystallites grew into orthorhombic Nb2O5 after post-annealing treatment. The Cr(VI) photoreduction property of both the as-anodized and annealed Nb2O5 samples obtained using an optimized condition (anodization voltage: 60 V, electrolyte temperature: 70 °C) was compared. Interestingly, the as-anodized Nb2O5 film was found to display better photoreduction of Cr(VI) than annealed Nb2O5. However, in terms of stability, the annealed Nb2O5 presented high photocatalytic efficiency for each cycle whereas the as-anodized Nb2O5 showed degradation in photocatalytic performance when used continually. [ABSTRACT FROM AUTHOR]

TiO2 nanotubes (TNTs) with self-aligned 7.25 ± 0.51-µm length, 66.78 ± 4.18-nm diameter, and 41.48 ± 4.31-nm wall thickness were fabricated using Ti wire in an anodic process using an ethylene glycol (EG)/NH4F–air bubbles electrolyte. The possible growth of TNTs in the electrolyte with different water content was explored. It was found that the growth rate of TNTs in an electrolyte with air bubbles and no water content was significantly faster than that in an electrolyte with 1–5-vol% water content. The degradation of methylene blue (MB) dye with sodium borohydride (NaBH4) as the sacrificial reagent (hole scavenger) under ultraviolet (UV) irradiation was investigated in a photocatalytic study of 400 °C annealed optimized TNTs. The results showed that TNTs can reduce MB at approximately 99%, 74%, and 40% removal efficiency using the first, second, and third cycles, respectively, for 70-min reaction time each. A kinetic study revealed that the photoreduction process followed the pseudo-first-order kinetic with reaction rates of 0.0280, 0.0213, and 0.0052 min−1 for the first, second, and third cycles, respectively. This study's findings will provide new insights into the design of UV light induced on anodized TNTs using Ti wire in EG/NH4F electrolytes with air bubbles aided by NaBH4 for the degradation of MB dye. [ABSTRACT FROM AUTHOR]

Heterogeneous photocatalysis based on semiconductor oxide is a promising technology for treating polluted industrial waste water. Cr(VI) is an example of toxic and mobile water pollutant originated mainly from industrial processes like steel industry and electroplating. The removal of Cr(VI) can be done by photoreduction on a surface of photocatalysts like TiO2nanotubes (TNTs). Here we describe a fast-rate formation of highly ordered TNTs via two steps anodization processes in an aged electrolyte containing fluoride-ethylene glycol. First step anodization was done for template formation as well as for saturating the electrolyte with TiF62– and second anodization was done to grow TNTs. The template was formed by removing initial anodic layer through sonication. Anodization voltage was kept constant at 60 V. After an hour of anodization, 22.70 μm long TNTs were formed with the rate of ∼350 nm/min. The as-anodized TNTs were then annealed in N2gas at different temperatures. The annealed TNTs were then used as photocatalyst for the photoreduction of Cr(VI) under sunlight in a parabolic trough reflector. The TNTs annealed at 450 °C in nitrogen show the best photoreduction activity with ∼80% Cr(VI) removal after 5 h exposure to sunlight. This is due to the presence of anatase TiO2as well as a possibility of nitrogen insertion, which may have narrowed the band gap of the oxide. [ABSTRACT FROM AUTHOR]

The KOH-ZrO2 solid electrolytes were prepared by sol-gel process. Ion conductivity and the conducting ion species were investigated from the impedance measurement and the electromotive force measurement. Resultant KOH-ZrO2 solid electrolyte showed high conductivity of 9×10−3 Scm−1 at 20°C and 60% relative humidity. Hydroxide ion was considered as the main charge carrier from the potentials of the water vapor concentration cells. All-solid state iron/air secondary batteries were successfully prepared with the composite negative electrode composed of sponge iron, KOH-ZrO2 electrolyte and carbon black. [ABSTRACT FROM AUTHOR]

Cesium dihydrogen phosphate (CsH2PO4, CDP) and dodecaphosphotungstic acid (H3PW12O40·nH2O, WPA·nH2O) were mechanochemically milled to synthesize CDP-WPA composites. The ionic conductivities of these composites were measured by an ac impedance method under anhydrous conditions. Despite the synthesis temperatures being much lower than the dehydration and phase-transition temperatures of CDP under anhydrous conditions, the ionic conductivities of the studied composites increased significantly. The highest ionic conductivity of 6.58×10-4 Scm-1 was achieved for the 95CDP·5WPA composite electrolyte at 170 °C under anhydrous conditions. The ionic conduction was probably induced in the percolated interfacial phase between CDP and WPA. The phenomenon of high ionic conduction differs for the CDP-WPA composite and pure CDP or pure WPA under anhydrous conditions. The newly developed hydrogen interaction between CDP and WPA supports anhydrous proton conduction in the composites. [ABSTRACT FROM AUTHOR]

The formation of TiO 2 nanotube arrays by anodisation of Ti in fluoride/ethylene glycol (EG) electrolyte added to it lithium hydroxide (LiOH) or potassium hydroxide (KOH) at 60 V for 60 min was investigated. Highly ordered 15 μm long TiO 2 nanotubes (TNTs) were produced in LiOH/fluoride/EG and 18 μm long TNTs were obtained in KOH/fluoride/EG. The as-anodized TNTs in these alkaline electrolytes were found to be crystalline and obviously annealing increases the crystallinity. Annealed TNTs were used as a photoanode in a backside illuminated dye-sensitized solar cell (DSSC). Photoconversion efficiency, η of 3% was achieved for sample with photoanode prepared in KOH/fluoride/EG higher than DSSC with TNTs photoanode fabricated in LiOH/fluoride/EG. [ABSTRACT FROM AUTHOR]

Abstract: Solid inorganic–organic composites were synthesized for the application as an electrolyte in fuel cells. CsHSO4 (CHS) was mechanochemically treated with Azole, which has a five-membered nitrogen heterocyclic ring such as imidazole (Iz), 1,2,4-triazole (Tz) and benzimidazole (Bz), in dry nitrogen atmosphere to obtain composites with xCHS·(100− x)Azole (x =90–50mol%). Chemical interactions between CHS and Azoles after solid-state mechanochemical treatment were confirmed from structural observation. The proton conductivity of the composites was largely increased by introduction of Azoles, particularly in the lower temperature region than a superprotic phase-transition temperature of CHS and melting points of Azoles. Proton conductivities of 80CHS·20Iz and 80CHS·20Tz composites ranged from 7×10−4 to 2×10−3 Scm−1 over a wide temperature range (60–160°C). However, CHS–Bz composites showed lower conductivities due to the lower reactivity of Bz. Proton transfer in CHS–Azole composite systems includes the proton-hopping mechanism and self-dissociation, which probably supports protic diffusion, especially in low temperature regions. [Copyright &y& Elsevier]

Abstract: Inorganic–organic composite electrolytes for use in dry fuel cells were synthesized from CsHSO4 (CHS) and 1,2,4-triazole (Tz). CHS and Tz were mechanochemically treated in a dry nitrogen atmosphere to obtain composites with xCHS·(100− x)Tz, where x is the amount (mol) and was varied in increments of 10 between 90 and 50. Structural investigation of the composites indicated that chemical interactions occurred between CHS and Tz after solid-state mechanochemical treatment. The proton conductivity of the composite electrolytes was largely increased by introduction of Tz, particularly in the low temperature region. The composite with x =80 showed high proton conductivity (6.0×10−4 to 1.60×10−3 Scm−1) over a wide temperature range (60–160°C) in a dry atmosphere. These observations suggest that proton transfer in the CHS and Tz composite systems includes the proton-hopping mechanism and self-dissociation. This phenomenon probably supports proton diffusion, especially in low temperature regions. [Copyright &y& Elsevier]

Abstract: Composite electrolytes composed of cesium hydrogen sulfate containing phosphotungstic acids (CsHSO4–H3PW12O40) and sulfonated poly(ether–ether ketone) (SPEEK) were prepared by casting the corresponding precursor for application in fuel cells. Partially Cs-substituted phosphotungstic acids (Cs x H3−x PW12O40) were formed in the CsHSO4–H3PW12O40 system by mechanochemical treatment. SPEEK was prepared from PEEK by sulfonation using concentrated sulfuric acid. Flexible composite electrolytes were obtained and their electrochemical properties were markedly improved with the addition of Cs x H3−x PW12O40, into the SPEEK matrix. A maximum power density of 213mWcm−2 was obtained from the single cell test for 50H3PW12O40–50CsHSO4 in SPEEK (1/5 by weight) composite electrolyte at 80°C and at 80 RH%. Electrochemical properties and transmission electron microscopy (TEM) results suggest that three-dimensional cluster particles were formed and homogeneously distributed in the SPEEK matrix. The mechanochemically synthesized Cs x H3−x PW12O40 incorporated into the SPEEK matrix increased the number of protonate sites in the electrolyte. The composite electrolytes were successfully formed with Cs x H3−x PW12O40, which consist of hydrogen bonding between surface of inorganic solid acids and not only –HSO4 − dissociated from CsHSO4 but also –SO3H groups in the SPEEK. [ABSTRACT FROM AUTHOR]

Abstract: Proton conducting poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) ultrathin layer was deposited on sol–gel-derived phenylsilsesquioxane (PhSiO3/2) particles via layer-by-layer (LbL) assembly technique. Spherical and size-controlled particles in the range of 0.3–4.0μm were successfully prepared by varying the condensation reaction. One PAMPS layer with 1.5nm thickness was deposited on the particle, the volume fractions of Primer/PAMPS-multilayer varied from 0.7 to 11vol.%. Sheet-like composite electrolytes in which PAMPS layer percolated throughout the sample can be obtained by hot-pressing the PAMPS-deposited PhSiO3/2 particles. The sample prepared using unmodified PhSiO3/2 exhibited a very low proton conductivity of 10−9 Scm−1 at 80°C, whereas the conductivity of the composite electrolytes increased significantly with a very small amount of PAMPS-multilayer (∼1vol.%). The composite with 11vol.% PAMPS exhibited 2×10−3 Scm−1 at 80°C and 95% of relative humidity. [Copyright &y& Elsevier]

Abstract: Ultrathin layers of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) were alternately deposited on the negatively charged phenylsilsesquioxane (PhSiO3/2) particles via Layer-by-Layer (LbL) technique. PDDA/PAMPS multilayer-deposited PhSiO3/2 particles once soften and glued together with plastic deformation at temperatures higher than the glass transition temperature. Sheet-like electrolytes prepared using multilayered PDDA/PAMPS-deposited PhSiO3/2 particles showed proton conductivities 4–6 orders of magnitude higher than those of the samples without multilayers, and the proton conductivity reached about 10−3 S/cm at 80 °C and 80% relative humidity. [Copyright &y& Elsevier]

Abstract: Thermally and chemically stable phenylsilsesquioxane (PhSiO3/2) particles were prepared by sol–gel process, and ultra-thin layers of oppositely charged poly(diallyldimethylammonium chloride) (PDDA) and dodecatungstophosphoric acid (WPA) were alternately deposited on the negative-charged PhSiO3/2 particles via layer-by-layer assembly technique. Hygroscopic property of WPA was remarkably reduced owing to the formation of PDDA/WPA complex. The amount of WPA adsorbed on PhSiO3/2 particles was estimated to be ∼0.03 (g/g PhSiO3/2). Transparent and monolithic pellet can be obtained from the resultant core–shell particles by pressing. Proton conductivity of WPA-deposited samples increased about 4 orders of magnitude compared with unmodified samples, and reached to about 10−4 S/cm at 80 °C and 80% relative humidity. [Copyright &y& Elsevier]

All solid-state nickel/metal hydride (Ni/MH) battery was fabricated by using a proton-conductive phosphoric acid-doped silica gel as an electrolyte. The H3PO4-doped silica gel was dried in vacuum at various temperatures for 1 h before fabricating the battery in order to reduce the possibility of corrosion by water on the surface and in the micropores of the gel. The influence of drying temperature on the crystallinity, water content and conductivity of the gel was investigated. The conductivity depended on the drying temperature of the gel. The fabricated all solid-state Ni/MH battery was able to operate several tens of charge–discharge cycles at relatively high current density although the utilization of the battery was low. [Copyright &y& Elsevier]

Novel single ion-conductive inorganic/organic composites were prepared from 95(0.6Li2S·0.4SiS2)·5Li4SiO4 oxysulfide glass and a high molecular weight branched poly(oxyethylene) (POE). The ionic conductivity of the composites increased with an increase of the glass. The ionic conductivity of the composite with 1 wt.% branched poly(oxyethylene) was in the orders of 10−5 S/cm at 30 °C and 10−4 S/cm at 80 °C. The composite exhibited an electrochemical stability window up to ca. 4.5 V versus Li+/Li and thermal stability against lithium metal up to 200 °C. Addition of LiClO4 to the polymer matrix of the composite improved the ionic conductivity. In this case, the composite was a dual-ion conductor, i.e., both Li+ and ClO4− contributed to the conductivity. [Copyright &y& Elsevier]