Recent Advancements in Polysulfone Based Membranes for Fuel Cell (PEMFCs, DMFCs and AMFCs) Applications: A Critical Review.

In recent years, ion electrolyte membranes (IEMs) preparation and properties have attracted fabulous attention in fuel cell usages owing to its high ionic conductivity and chemical resistance. Currently, perfluorinatedsulfonicacid (PFSA) membrane has been widely employed in the membrane industry in polymer electrolyte membrane fuel cells (PEMFCs); however, NafionTM suffers reduced proton conductivity at a higher temperature, requiring noble metal catalyst (Pt, Ru, and Pt-Ru), and catalyst poisoning by CO. Non-fluorinated polymers are a promising substitute. Polysulfone (PSU) is an aromatic polymer with excellent characteristics that have attracted membrane scientists in recent years. The present review provides an up-to-date development of PSU based electrolyte membranes and its composites for PEMFCs, alkaline membrane fuel cells (AMFCs), and direct methanol fuel cells (DMFCs) application. Various fillers encapsulated in the PEM/AEM moiety are appraised according to their preliminary characteristics and their plausible outcome on PEMFC/DMFC/AMFC. The key issues associated with enhancing the ionic conductivity and chemical stability have been elucidated as well. Furthermore, this review addresses the current tasks, and forthcoming directions are briefly summarized of PEM/AEMs for PEMFCs, DMFCs, AMFCs.

Decoration of CuO NWs Gas Sensor with ZnO NPs for Improving NO2 Sensing Characteristics.

This paper introduces a method for improving the sensitivity to NO2 gas of a p-type metal oxide semiconductor gas sensor. The gas sensor was fabricated using CuO nanowires (NWs) grown through thermal oxidation and decorated with ZnO nanoparticles (NPs) using a sol-gel method. The CuO gas sensor with a ZnO heterojunction exhibited better sensitivity to NO2 gas than the pristine CuO gas sensor. The heterojunction in CuO/ZnO gas sensors caused a decrease in the width of the hole accumulation layer (HAL) and an increase in the initial resistance. The possibility to influence the width of the HAL helped improve the NO2 sensing characteristics of the gas sensor. The growth morphology, atomic composition, and crystal structure of the gas sensors were analyzed using field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction, respectively.

Sensitivity Improvement of Urchin-Like ZnO Nanostructures Using Two-Dimensional Electron Gas in MgZnO/ZnO.

This paper introduces a strategy for improving the sensitivity of a gas sensor to NO2 gas. The gas sensor was fabricated using urchin-like ZnO nanostructures grown on MgO particles via vapor-phase growth and decorated with MgZnO nanoparticles via a sol-gel process. The urchin-like ZnO gas sensor decorated with MgZnO showed higher sensitivity to NO2 gas than a pristine urchin-like ZnO gas sensor. When ZnO and MgZnO form a heterojunction, a two-dimensional electron gas is generated. This improves the performance of the fabricated gas sensor. The growth morphology, atomic composition, and phase structure were confirmed through field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction, respectively.

Effect of the cobalt and zinc ratio on the preparation of zeolitic imidazole frameworks (ZIFs): synthesis, characterization and supercapacitor applications.

The effect of the cobalt nitrate hexahydrate/zinc nitrate hexahydrate molar ratio on the physicochemical features of the zeolitic imidazole framework (ZIF) was studied. ZIFs were prepared by using 2-methyl imidazole as the cross-linker at room temperature without any additives in methanol solution. From the obtained results, it was found that the Co/Zn ratio has a tremendous impact on the surface area, crystallinity, pore diameter and electrochemical performance of ZIFs. Upon increasing the Co/Zn content the surface area, pore volume, pore diameter and specific capacitance decreased. The maximum BET surface area was found to be 1043.65 m2 g-1 for ZIF Co/Zn = 0.5. The present work offers a new intuition in relation to the role of the Co/Zn ratio in the synthesis method of ZIFs.

Improved Sensitivity of α-Fe2O3 Nanoparticle-Decorated ZnO Nanowire Gas Sensor for CO.

A strategy for improving the sensitivity of a sensor for detecting CO and NH3 gases is presented herein. The gas sensor was fabricated from ZnO metal oxide semiconductor nanostructures grown via a vapor⁻liquid⁻solid process and decorated with α-Fe2O3 nanoparticles via a sol⁻gel process. The response was enhanced by the formation of an α-Fe2O3/ZnO n⁻n heterojunction and the growth of thinner wires. ZnO nanowires were grown on indium⁻tin⁻oxide glass electrodes using Sn as a catalyst for growth instead of Au. The structure and elemental composition were investigated using field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The gas sensing results indicate that the response value to 100 ppm CO was 18.8 at the optimum operating temperature of 300 °C.

Improved Electrical Performance of SiO2-Doped Indium Zinc Oxide Thin-Film Transistor.

In this study, we investigated the effect of oxygen content on the stability and the role of silicon in amorphous SiO2-doped indium-zinc-oxide thin film transistor. The SiO2-doped IZO (SIZO) thinfilms were deposited at room temperature by radio-frequency magnetron co-sputtering. To optimize stability and electrical performance, we changed the amount of oxygen by changing oxygen gas ratio in reactive sputtering (11%, 12%, and 13%) and used SiO2 target to deposit SIZO active layer. By adjusting the parameters of SIZO thin-film transistor (TFT) preparation, we found that the best performance was obtained when the oxygen ratio of a-SIZO films was 11%. The optimized a-SIZO TFT exhibited an on/off current ratio (Ion/Ioff) of 2.1×107, saturation mobility (µsat) of 53.6 cm²/V . s, threshold voltage (Vth) of -7.3 V, and subthreshold swing (S.S.) of 1.7 V/decade. Compared to a-IZO films, the a-SIZO film showed better stability and electrical performance because it had fewer oxygen vacancies and defects.

Improvement in the Electrical Performance of Ge-Doped InZnO Thin-Film Transistor.

We fabricated amorphous oxide semiconductor thin-film transistors (TFTs) using Ge-doped InZnO (Ge-IZO) thin films as active-channel layers. The Ge-IZO thin films were deposited at room temperature by radio-frequency (RF) magnetron co-sputtering system, and then annealed in air for 1 h at 300 °C. Some processing parameters such as sputtering oxygen partial pressure [O2/(Ar + O2)] and sputtering power for GeO2 target were changed to investigate what was the optimal amount of Ge in the Ge-IZO active layer. A small concentration of Ge added to IZO by co-sputtering enhanced the carrier concentration, mobility, and conductivity; but further increase in Ge concentration degraded the device performance. In order to optimize the electrical properties of Ge-IZO TFTs, we tried to adjust the processing parameters and the best Ge-IZO TFT was obtained at a co-sputtering oxygen partial pressure of 2% and GeO2 target power of 10 W. The fabricated Ge-IZO TFT exhibited an on/off ratio of 3.0 x 10(7), a saturation mobility of 13.05 cm2/V·s, a subthreshold swing of 0.95 V/dec, and a threshold voltage of 0 V. XPS and XRD analyses of Ge-IZO films were performed to investigate the binding energies of atoms in Ge-IZO films and the crystallinity of the films. 90% transmittance of visible light was achieved, which makes the technology useful for transparent devices.

Effects of Double Active Layer and Acetic Acid Stabilizer on the Electrical Properties of a Solution-Processed Zinc Tin Oxide Thin-Film Transistor.

We investigated the effects of a double active layer (DAL) and acetic acid stabilizer on zinc tin oxide (ZTO) thin-film transistors (TFTs) fabricated using a solution process. The DAL was composed of two layers created by a ZTO solution doped with the same or different percentiles of an atomic Sn concentration (30 at.%, 60 at.%). The electrical performance of the ZTO TFTs significantly was improved after we added acetic acid (AA) instead of monoethanolamine (MEA). This was accomplished by applying a type 2 DAL (bottom layer: Sn 60 at.%, top layer: Sn 30 at.%, 60/30) instead of other types (30/30 or 60/60). It was demonstrated that AA plays a role in lowering the decomposition temperature, enhancing the metal-oxygen bridge, and decreasing hydroxyl groups in the film. In addition, the type 2 DAL structure (60/30) lowered the Ioff of the ZTO TFT and controlled the carrier concentration in the channel. The best performances were obtained at a Sn concentration of 60 at.% in the bottom ZTO layer and 30 at.% in the top ZTO layer, with AA added as a stabilizer. The ZTO TFT exhibited an on/off ratio of 1.1 x 10(9), a saturation mobility of 5.04 cm2/V·s, a subthreshold slope of 0.11 V/decade, and a threshold voltage of 1.6 V.