Research

18 pages, 46024 KiB

Open AccessArticle

The Effect of Sulfated Zirconia and Zirconium Phosphate Nanocomposite Membranes on Fuel-Cell Efficiency

by Rudzani Sigwadi, Touhami Mokrani, Phumlani Msomi and Fulufhelo Nemavhola

Polymers 2022, 14(2), 263; https://doi.org/10.3390/polym14020263 - 10 Jan 2022

Cited by 12 | Viewed by 2360

To investigate the effect of acidic nanoparticles on proton conductivity, permeability, and fuel-cell performance, a commercial Nafion^® 117 membrane was impregnated with zirconium phosphates (ZrP) and sulfated zirconium (S-ZrO₂) nanoparticles. As they are more stable than other solid superacids, sulfated [...] Read more.

To investigate the effect of acidic nanoparticles on proton conductivity, permeability, and fuel-cell performance, a commercial Nafion^® 117 membrane was impregnated with zirconium phosphates (ZrP) and sulfated zirconium (S-ZrO₂) nanoparticles. As they are more stable than other solid superacids, sulfated metal oxides have been the subject of intensive research. Meanwhile, hydrophilic, proton-conducting inorganic acids such as zirconium phosphate (ZrP) have been used to modify the Nafion^® membrane due to their hydrophilic nature, proton-conducting material, very low toxicity, low cost, and stability in a hydrogen/oxygen atmosphere. A tensile test, water uptake, methanol crossover, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to assess the capacity of nanocomposite membranes to function in a fuel cell. The modified Nafion^® membrane had a higher water uptake and a lower water content angle than the commercial Nafion^® 117 membrane, indicating that it has a greater impact on conductivity. Under strain rates of 40, 30, and 20 mm/min, the nanocomposite membranes demonstrated more stable thermal deterioration and higher mechanical strength, which offers tremendous promise for fuel-cell applications. When compared to 0.113 S/cm and 0.013 S/cm, respectively, of commercial Nafion^® 117 and Nafion^® ZrP membranes, the modified Nafion^® membrane with ammonia sulphate acid had the highest proton conductivity of 7.891 S/cm. When tested using a direct single-cell methanol fuel cell, it also had the highest power density of 183 mW cm⁻² which is better than commercial Nafion^® 117 and Nafion^® ZrP membranes. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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16 pages, 3811 KiB

Open AccessArticle

Hybrid Proton-Exchange Membrane Based on Perfluorosulfonated Polymers and Resorcinol–Formaldehyde Hydrogel

by Alexandra Maria Isabel Trefilov, Adriana Balan and Ioan Stamatin

Polymers 2021, 13(23), 4123; https://doi.org/10.3390/polym13234123 - 26 Nov 2021

Cited by 5 | Viewed by 1792

Abstract

Organic resorcinol–formaldehyde (RF) hydrogels were introduced into a hybrid cation-exchange membrane in order to enhance its following properties: water uptake, thermal stability, and ionic conductivity. This study was aimed to investigate the modifications induced by the RF organic clusters that form a uniform [...] Read more.

Organic resorcinol–formaldehyde (RF) hydrogels were introduced into a hybrid cation-exchange membrane in order to enhance its following properties: water uptake, thermal stability, and ionic conductivity. This study was aimed to investigate the modifications induced by the RF organic clusters that form a uniform distributed network within the perflourosulfonated acid (PFSA) matrix. RF concentration was controlled by resorcinol and formaldehyde impregnation time using water or ethanol solvents. The specific morphological and structural properties were characterized by atomic force microscopy, UV–Vis, and Fourier transform infrared spectroscopy. Thermo-gravimetric analysis was employed to study the thermal stability and degradation processes of the composite membranes. Proton conductivity, as a function of relative humidity (RH) at 80 °C, was measured using in-plane four-point characterization technique. Compared to the pristine membrane, the PFSA–RF hybrid membranes showed improved thermal stability at up to 46 °C and higher ionic conductivity for low RF content, especially at low relative humidity, when using ethanol-based solvents. Single fuel cell testing on RF-based membrane–electrode assembly revealed impeccable fuel crossover and power performance at 80 °C and 40% relative humidity, delivering a 76% increase in power density compared to a reference assembled with a pristine membrane and the same catalyst loadings. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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14 pages, 4347 KiB

Open AccessArticle

Novel Crosslinked Sulfonated PVA/PEO Doped with Phosphated Titanium Oxide Nanotubes as Effective Green Cation Exchange Membrane for Direct Borohydride Fuel Cells

by Marwa H. Gouda, Noha A. Elessawy and Arafat Toghan

Polymers 2021, 13(13), 2050; https://doi.org/10.3390/polym13132050 - 23 Jun 2021

Cited by 21 | Viewed by 2244

Abstract

A direct borohydride fuel cell (DBFC) is a type of low temperature fuel cell which requires efficient and low cost proton exchange membranes in order to commercialize it. Herein, a binary polymer blend was formulated from inexpensive and ecofriendly polymers, namely polyethylene oxide [...] Read more.

A direct borohydride fuel cell (DBFC) is a type of low temperature fuel cell which requires efficient and low cost proton exchange membranes in order to commercialize it. Herein, a binary polymer blend was formulated from inexpensive and ecofriendly polymers, namely polyethylene oxide (PEO) and poly vinyl alcohol (PVA). Phosphated titanium oxide nanotube (PO₄TiO₂) was synthesized from a simple impregnation–calcination method and later embedded for the first time as a doping agent into this polymeric matrix with a percentage of 1–3 wt%. The membranes’ physicochemical properties such as oxidative stability and tensile strength were enhanced with increasing doping addition, while the borohydride permeability, water uptake, and swelling ratio of the membranes decreased with increasing PO₄TiO₂ weight percentage. However, the ionic conductivity and power density increased to 28 mS cm⁻¹ and 72 mWcm⁻² respectively for the membrane with 3 wt% of PO₄TiO₂ which achieved approximately 99% oxidative stability and 40.3 MPa tensile strength, better than Nafion117 (92% RW and 25 MPa). The fabricated membrane with the optimum properties (PVA/PEO/PO₄TiO₂-3) achieved higher selectivity than Nafion117 and could be efficient as a proton exchange membrane in the development of green and low cost DBFCs. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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12 pages, 5983 KiB

Open AccessArticle

Enhanced Ion Cluster Size of Sulfonated Poly (Arylene Ether Sulfone) for Proton Exchange Membrane Fuel Cell Application

by Prem P. Sharma, Vo Dinh Cong Tinh and Dukjoon Kim

Polymers 2021, 13(7), 1111; https://doi.org/10.3390/polym13071111 - 31 Mar 2021

Cited by 11 | Viewed by 2976

Abstract

A successful approach towards enhancement in ion cluster size of sulfonated poly (arylene ether sulfone) (SPAES)-based membranes has been successfully carried out by encapsulating basic pendent branches as side groups. Modified SPAES was synthesized by condensation polymerization followed by bromination with N-bromosuccinamide (NBS) [...] Read more.

A successful approach towards enhancement in ion cluster size of sulfonated poly (arylene ether sulfone) (SPAES)-based membranes has been successfully carried out by encapsulating basic pendent branches as side groups. Modified SPAES was synthesized by condensation polymerization followed by bromination with N-bromosuccinamide (NBS) and sulfonation by ring opening reaction. Various molar ratios of branched polyethyleneimine (PEI) were added to the SPAES and the developed polymer was designated as SPAES-x-PEI-y, where x denoted the number of sulfonating acid group per polymer chain and y represents the amount of PEI concentration. Polymer synthesis was characterized by ¹H-NMR (Nuclear magnetic resonance) and FT-IR (Fourier-transform infrared spectroscopy) analysis. A cumulative trend involving enhanced proton conductivity of the membranes with an increase in the molar ratio of PEI has been observed, clearly demonstrating the formation of ionic clusters. SPAES-140-PEI-3 membranes show improved proton conductivity of 0.12 Scm⁻¹ at 80 °C. Excellent chemical stability was demonstrated by the polymer with Fenton’s test at 80 °C for 24 h without significant loss in proton conductivity, owing to the suitability of the synthesized hybrid membrane for electrochemical application. Moreover, a single cell degradation test was conducted at 80 °C showing a power density at a 140 mWcm⁻² value, proving the stable nature of synthesized membranes for proton exchange membrane fuel cell application. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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20 pages, 4685 KiB

Open AccessArticle

Exploring the Structure–Performance Relationship of Sulfonated Polysulfone Proton Exchange Membrane by a Combined Computational and Experimental Approach

by Cataldo Simari, Mario Prejanò, Ernestino Lufrano, Emilia Sicilia and Isabella Nicotera

Polymers 2021, 13(6), 959; https://doi.org/10.3390/polym13060959 - 20 Mar 2021

Cited by 20 | Viewed by 3156

Abstract

Sulfonated Polysulfone (sPSU) is emerging as a concrete alternative to Nafion ionomer for the development of proton exchange electrolytic membranes for low cost, environmentally friendly and high-performance PEM fuel cells. This ionomer has recently gained great consideration since it can effectively combine large [...] Read more.

Sulfonated Polysulfone (sPSU) is emerging as a concrete alternative to Nafion ionomer for the development of proton exchange electrolytic membranes for low cost, environmentally friendly and high-performance PEM fuel cells. This ionomer has recently gained great consideration since it can effectively combine large availability on the market, excellent film-forming ability and remarkable thermo-mechanical resistance with interesting proton conductive properties. Despite the great potential, however, the morphological architecture of hydrated sPSU is still unknown. In this study, computational and experimental advanced tools are combined to preliminary describe the relationship between the microstructure of highly sulfonated sPSU (DS = 80%) and its physico-chemical, mechanical and electrochemical features. Computer simulations allowed for describing the architecture and to estimate the structural parameters of the sPSU membrane. Molecular dynamics revealed an interconnected lamellar-like structure for hydrated sPSU, with ionic clusters of about 14–18 Å in diameter corresponding to the hydrophilic sulfonic-acid-containing phase. Water dynamics were investigated by ¹H Pulsed Field Gradient (PFG) NMR spectroscopy in a wide temperature range (20–120 °C) and the self-diffusion coefficients data were analyzed by a “two-sites” model. It allows to estimate the hydration number in excellent agreement with the theoretical simulation (e.g., about 8 mol H₂O/mol SO₃⁻ @ 80 °C). The PEM performance was assessed in terms of dimensional, thermo-mechanical and electrochemical properties by swelling tests, DMA and EIS, respectively. The peculiar microstructure of sPSU provides a wider thermo-mechanical stability in comparison to Nafion, but lower dimensional and conductive features. Nonetheless, the single H₂/O₂ fuel cell assembled with sPSU exhibited better features than any earlier published hydrocarbon ionomers, thus opening interesting perspectives toward the design and preparation of high-performing sPSU-based PEMs. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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15 pages, 2010 KiB

Open AccessArticle

Ex-Situ Evaluation of Commercial Polymer Membranes for Vanadium Redox Flow Batteries (VRFBs)

by Nana Zhao, Harry Riley, Chaojie Song, Zhengming Jiang, Keh-Chyun Tsay, Roberto Neagu and Zhiqing Shi

Polymers 2021, 13(6), 926; https://doi.org/10.3390/polym13060926 - 17 Mar 2021

Cited by 8 | Viewed by 2122

Abstract

Polymer membranes play a vital role in vanadium redox flow batteries (VRFBs), acting as a separator between the two compartments, an electronic insulator for maintaining electrical neutrality of the cell, and an ionic conductor for allowing the transport of ionic charge carriers. It [...] Read more.

Polymer membranes play a vital role in vanadium redox flow batteries (VRFBs), acting as a separator between the two compartments, an electronic insulator for maintaining electrical neutrality of the cell, and an ionic conductor for allowing the transport of ionic charge carriers. It is a major influencer of VRFB performance, but also identified as one of the major factors limiting the large-scale implementation of VRFB technology in energy storage applications due to its cost and durability. In this work, five (5) high-priority characteristics of membranes related to VRFB performance were selected as major considerable factors for membrane screening before in-situ testing. Eight (8) state-of-the-art of commercially available ion exchange membranes (IEMs) were specifically selected, evaluated and compared by a set of ex-situ assessment approaches to determine the possibility of the membranes applied for VRFB. The results recommend perfluorosulfonic acid (PFSA) membranes and hydrocarbon anion exchange membranes (AEMs) as the candidates for further in-situ testing, while one hydrocarbon cation exchange membrane (CEM) is not recommended for VRFB application due to its relatively high VO²⁺ ion crossover and low mechanical stability during/after the chemical stability test. This work could provide VRFB researchers and industry a valuable reference for selecting the polymer membrane materials before VRFB in-situ testing. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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13 pages, 17138 KiB

Open AccessArticle

Polystyrene-Based Hydroxide-Ion-Conducting Ionomer: Binder Characteristics and Performance in Anion-Exchange Membrane Fuel Cells

by Ji Eon Chae, So Young Lee, Sung Jong Yoo, Jin Young Kim, Jong Hyun Jang, Hee-Young Park, Hyun Seo Park, Bora Seo, Dirk Henkensmeier, Kwang Ho Song and Hyoung-Juhn Kim

Polymers 2021, 13(5), 690; https://doi.org/10.3390/polym13050690 - 25 Feb 2021

Cited by 14 | Viewed by 3675

Abstract

Polystyrene-based polymers with variable molecular weights are prepared by radical polymerization of styrene. Polystyrene is grafted with bromo-alkyl chains of different lengths through Friedel–Crafts acylation and quaternized to afford a series of hydroxide-ion-conducting ionomers for the catalyst binder for the membrane electrode assembly [...] Read more.

Polystyrene-based polymers with variable molecular weights are prepared by radical polymerization of styrene. Polystyrene is grafted with bromo-alkyl chains of different lengths through Friedel–Crafts acylation and quaternized to afford a series of hydroxide-ion-conducting ionomers for the catalyst binder for the membrane electrode assembly in anion-exchange membrane fuel cells (AEMFCs). Structural analyses reveal that the molecular weight of the polystyrene backbone ranges from 10,000 to 63,000 g mol⁻¹, while the ion exchange capacity of quaternary-ammonium-group-bearing ionomers ranges from 1.44 to 1.74 mmol g⁻¹. The performance of AEMFCs constructed using the prepared electrode ionomers is affected by several ionomer properties, and a maximal power density of 407 mW cm⁻² and a durability exceeding that of a reference cell with a commercially available ionomer are achieved under optimal conditions. Thus, the developed approach is concluded to be well suited for the fabrication of next-generation electrode ionomers for high-performance AEMFCs. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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12 pages, 6387 KiB

Open AccessArticle

A Robust Composite Proton Exchange Membrane of Sulfonated Poly (Fluorenyl Ether Ketone) with an Electrospun Polyimide Mat for Direct Methanol Fuel Cells Application

by Geng Cheng, Zhen Li, Shan Ren, Dongmei Han, Min Xiao, Shuanjin Wang and Yuezhong Meng

Polymers 2021, 13(4), 523; https://doi.org/10.3390/polym13040523 - 10 Feb 2021

Cited by 13 | Viewed by 2398

Abstract

As a key component of direct methanol fuel cells, proton exchange membranes with suitable thickness and robust mechanical properties have attracted increasing attention. On the one hand, a thinner membrane gives a lower internal resistance, which contributes highly to the overall electrochemical performance [...] Read more.

As a key component of direct methanol fuel cells, proton exchange membranes with suitable thickness and robust mechanical properties have attracted increasing attention. On the one hand, a thinner membrane gives a lower internal resistance, which contributes highly to the overall electrochemical performance of the cell, on the other hand, strong mechanical strength is required for the application of proton exchange membranes. In this work, a sulfonated poly (fluorenyl ether ketone) (SPFEK)-impregnated polyimide nanofiber mat composite membrane (PI@SPFEK) was fabricated. The new composite membrane with a thickness of about 55 μm exhibited a tensile strength of 35.1 MPa in a hydrated state, which is about 65.8% higher than that of the pristine SPFEK membrane. The antioxidant stability test in Fenton’s reagent shows that the reinforced membrane affords better oxidation stability than does the pristine SPFEK membrane. Furthermore, the morphology, proton conductivity, methanol permeability, and fuel cell performance were carefully evaluated and discussed. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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