High-temperature proton-exchange membrane fuel cells (HT-PEMFCs) are mostly based on acid-doped membranes composed of polybenzimidazole (PBI). A severe drawback of acid-doped membranes is the deterioration of mechanical properties upon increasing acid-doping levels. Cross-linking of different polymers is a way to mitigate stability issues. In this study, a new ion-pair-coordinated membrane (IPM) system with quaternary ammonium groups for the application in HT-PEMFCs is introduced. PBI cross-linked with poly­(vinylbenzyl chloride) and quaternized with three amines (DABCO, quinuclidine, and quinuclidinol) are manufactured and compared to the state-of-the-art commercial Dapazol PBI membrane ex situ as well as by evaluating their HT-PEMFC performance. The IPMs show reduced swelling and better mechanical properties upon doping, which enables a reduction in membrane thickness while maintaining a comparably low gas crossover and mechanical stability. The HT-PEMFC based on the best-performing IPM reaches up to 530 mW cm–2 at 180 °C under H2/air conditions at ambient pressure, while Dapazol is limited to less than 430 mW cm–2 at equal parameters. This new IPM system requires less acid doping than conventional PBI membranes while outperforming conventional PBI membranes, which renders these new membranes promising candidates for application in HT-PEMFCs.

The synthesis of new C60 fullerene derivatives functionalized with thiophene moieties as well as with electron donating or electron withdrawing groups, bromine (Br) or cyano (CN), respectively, using Bingel reactions is reported. The synthesized derivatives were used as the electron transporting materials (ETMs) in inverted perovskite solar cells (PSCs). Compared to devices fabricated with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), the new derivatives showed similar electrochemical properties and electron mobilities. However, PSCs based on the new derivatives synthesized in this work exhibited higher power conversion efficiencies (PCEs) than PC61BM based devices, which were ascribed to their better passivation ability, likely due to specific interactions between the fullerene addend and the perovskite layer surface. Devices based on the fullerene bearing the CN group exhibited an additionally improved efficiency due to the increased dielectric constant (εr) of this derivative. These results show that the new functionalized fullerene derivatives can act as efficient ETMs in inverted PSCs.

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The first example of a new class of carbon‐rich molecules is introduced, namely, a derivative of tetraethynyl[5]cumulene (TE5C). The use of sterically demanding pendent groups is the decisive structural feature to provide a stable product. Whereas triisopropylsilyl groups are seemingly not sufficiently large to afford an isolable cumulene product, switching to the larger tris(3,5‐di‐tert‐butylphenyl)methyl (‘supertrityl’) groups gives a crystalline, stable compound ([5]TE). The structural and electronic properties of [5]TE are examined in comparison to its closest known molecular relatives, tetraaryl[5]cumulenes.

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In this study, it is aimed to examine the opinions of teachers' self-directed learning skills with semi-structured interview form.The participants include 40 teachers from a primary and two secondary schools in Kartepe ( the district of Kocaeli). Self-Directed Learning Interview Form which has been designed by reading the relevant literature and seeking the experts’ opinions includes five questions related to phases of Self Direction in learning. The form was administered teachers face to face mostly.The interviews were audiorecorded and then transcribed by the researchers.The results of this represent each phase of Self-Directed Learning and also consistent with the studies in the literature

Quaternized Polybenzimidazole-Cross-Linked Poly(vinylbenzyl chloride) Membranes and Their Performance in HT-PEMFCs Keywords: Proton-exchange membrane, ion pair, high-temperature, phosphoric acid, quaternary ammonium, hydrogen crossover High temperature proton-exchange membrane fuel cells (HT-PEMFCs) are promising electrochemical energy conversion devices for the hydrogen economy. In this fuel cell type, phosphoric acid is immobilized as an electrolyte within a polybenzimidazole (PBI) membrane acting as a matrix. These membrane systems allow operating temperatures up to 200 °C, which is significantly higher than for sulfonated polymers that are used in low temperatures PEMFCs at around 80 °C. Operating PEMFCs above 100 °C harbors advantages such as faster reaction kinetics, higher tolerances against fuel impurities, and easier cooling. Nonetheless, phosphoric acid doped membranes also is the main challenge and drawback of these systems due to leaching of the dopant over time. A high acid-oping level is desired since it ensures high proton conductivity. However, the mechanical properties of PBI-based materials generally deteriorate upon increasing acid doping levels. In this regard, cross-linking PBI with another polymer is a promising route to enhance the mechanical properties of acid-doped membranes. Further, polymers with specific functional groups, such as quaternary ammonium (QA), can be used as cross-linkers to enhance the retention of phosphoric acid by forming strong interactions with biphosphate anions. Here, we present a new ion-pair-coordinated membrane (IPM) system decorated with QA groups. Poly(vinylbenzyl chloride) is used as a macromolecular cross-linker for PBI, and three different amines (Quinuclidine, Quinuclidinol, DABCO) are used as quaternizing agents. The performance of these membranes is evaluated ex-situ as well as electrochemically within HT-PEMFC operation and compared to a commercial m-PBI membrane (Dapazol). The IPMs show reduced swelling and better mechanical properties upon doping. Further, the commercial reference can be outperformed within HT-PEMFC operation at less acid doping than conventional PBI membranes. The best-performing IPM led to a 25% improved fuel cell performance. The peak power density of an HT-PEMFC incorporating a Dapazol membrane was 430 mW cm–2 at 180 °C under H2/air conditions and at ambient pressure, while the HT-PEMFC with the best-performing IPM yielded 530 cm–2 at equal parameters. Further, the hydrogen gas crossover of the IPMs is similar or less than that of the commercial reference even at lower membrane thicknesses, which renders these membranes as promising candidates for application in HT-PEMFC.

Alternative energy studies are crucial since the energy demand in the world increases rapidly. Nowadays, due to limited reserves of fossil fuel and CO2 emission, environmentally green energy is the most promising and desirable energy source for the future. In this context, fuel cells becoming one of the most promising alternative energy conversion devices. Especially polymer electrolyte membrane fuel cells (PEMFCs) are of great research interest. Theoverall efficiency of PEMFCs is strongly influenced by the polymer membrane placed between the anode and cathode. The current state-of-the-art perfluorosulfonic acid (PFSA)-based membranes used in PEMFCs, such as Nafion, rely on the presence of water as the charge carrier for an efficient proton conductivity, and operate usually only up to 80 °C. Therefore, Nafion-based systems require water management, which can be avoided by using polybenzimidazole (PBI)-based membranes instead; operating at higher temperatures (up to 180 °C). Nevertheless, pristine PBI-based membranes need to be doped with acid in order to produce a highly proton conductive system. In this context, phosphoric acid (PA) is the most promising acid as the proton conduction medium. PA doping levels are essential as they govern conductivity, while an excess acid doping can deteriorate mechanical and thermal properties of the membrane. Therefore, the optimization and determination of the doping levels are important for high temperature polymer electrolyte membrane fuel cells. Commonly, titration or weighing of the membranes are used for the determination of the acid doping level, but they suffer from low accuracy and precision. In this work, the acid doping level (ADL) of PBI-based membranes was studied by Raman, impedance, and energy-dispersive X-ray (EDX) spectroscopy, gravimetric and thermogravimetric analysis, and titration. The use of Raman spectroscopy is of great interest due to its non-destructive nature. It can be performed on the sample prior or post application in a HT-PEMFC. This study presents a new measurement protocol for ADLs by using Raman spectroscopy, which is a helpful tool for choosing the optimal ADL for a PBI-based membrane. Thus, the manufacturing process of high temperature fuel cells and their overall efficiency can be optimized. Keywords: Acid Doping Level (ADL), Fuel Cells (FCs), High Temperature (HT), Polymer Electrolyte Membrane (PEM), Phosphoric Acid (PA), Polybenzimidazole (PBI)