| 1. |
- Ansarian, Zahra, et al.
(author)
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Titanium germanium carbide MAX phase electrocatalysts for supercapacitors and alkaline water electrolysis processes
- 2023
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In: Materials Today Chemistry. - : Elsevier BV. - 2468-5194. ; 33
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Journal article (peer-reviewed)abstract
- Developing electrochemically active, stable, and low-cost electrocatalysts for electrochemical devices is a significant breakthrough. Accordingly, MAX phases, emerging three-dimensional materials, are considered outstanding candidates due to their excellent electrocatalytic and electrochemical properties. Herein, the titanium germanium carbide (Ti3GeC2) MAX phase with a layered structure manufactured through reactive sintering was regarded as the electrocatalyst. In the current work, the electrocatalytic activity of the Ti3GeC2 was investigated for electrochemical devices. It was observed that adding activated carbon to the Ti3GeC2 enhances the conductivity and active area, leading to an excellent specific capacitance (349 Fg-1) for supercapacitors. Also, the capacitance of Ti3GeC2 was increased by increasing the number of cyclic voltammetry cycles. In another application, Ti3GeC2 showed substantial activity for hydrogen and oxygen evolution reactions in alkaline media. As a result, the alkaline water electrolysis system using Ti3GeC2 showed the highest current density of 10 mA cm−2 at 1.36 V and outstanding stability over 400 cycles.
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| 2. |
- Khataee, Amirreza, et al.
(author)
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Poly(arylene alkylene)s functionalized with perfluorosulfonic acid groups as proton exchange membranes for vanadium redox flow batteries
- 2023
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In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 671
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Journal article (peer-reviewed)abstract
- With the aim to develop vanadium redox flow battery (VRFB) membranes beyond state of the art, we have in the present work functionalized poly(p-terphenylene)s with highly acidic perfluorosulfonic groups and investigated their performance as proton exchange membranes (PEMs). Consequently, two poly(p-terphenylene alkylene)s tethered with perfluoroalkylsulfonic acid and perfluorophenylsulfonic acid, respectively, were synthesized through superacid-mediated polyhydroxyalkylations and cast into PEMs. Compared with Nafion 212, the PEM carrying perfluorophenylsulfonic acid groups (PTPF-Phenyl-SA) was found to exhibit higher ionic conductivity and eight times lower vanadium (IV) permeation rate. The latter explains the longer self-discharge duration of the VRFB based on the PTPF-Phenyl-SA. In addition, the VRFB assembled with the PTPF-Phenyl-SA PEM exhibited a high average coulombic efficiency of 99.6% for over 100 cycles with a capacity fade of 0.24% per cycle, which was 50% lower than when Nafion 212 was used. More importantly, excellent capacity retention was achieved through electrochemical rate performance experiments at different current densities.
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| 3. |
- Salmeron-Sanchez, Ivan, et al.
(author)
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Zwitterionic poly(terphenylene piperidinium) membranes for vanadium redox flow batteries
- 2023
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 474
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Journal article (peer-reviewed)abstract
- Over recent years, non-fluorinated ion exchange membranes based on poly(terphenylene) backbones carrying different functional groups have shown potential application for vanadium redox flow batteries (VRFBs). Generally, the ion exchange membrane in VRFBs is a critical component in terms of the output power, long-term stability and cost. Yet, the shortcomings of commercial membranes (e.g., Nafion) have become a substantial barrier to further commercializing VRFBs. After successfully fabricating and testing poly(terphenylene)-based membranes carrying piperidinium and sulfonic acid groups, respectively, for VRFBs, we have in the present work combined both these ionic groups in a single zwitterionic membrane. A series of poly(terphenylene)-based membranes containing zwitterionic (sulfoalkylated piperidinium) and cationic (piperidinium) groups in different ratios (40–60%) were synthesized and investigated. The VRFB using the zwitterionic membranes showed competitive performance compared to Nafion 212 regarding ionic conductivity, capacity retention, and chemical stability. In addition, it was shown that the VRFB performance was improved by increasing the content of zwitterionic groups within the membrane. A self-discharge time of more than 800 h and 78.7% average capacity retention for 500 VRFB cycles were achieved using a membrane with an optimized ratio (60% zwitterionic and 40% piperidinium groups). Furthermore, the chemical stability was promising, as there was no change in the chemical structure after 500 cycles. Our results represent a critical step for developing novel and competitive ion exchange membranes as an excellent alternative to the Nafion benchmark.
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