Ionomers From Kraft Lignin for Renewable Energy Applications

Farzin, Seefat; Johnson, Tyler J.; Chatterjee, Snigdhansu; Zamani, Ehsan; Dishari, Shudipto Konika

doi:10.3389/fchem.2020.00690

Cited by 15 publications

(30 citation statements)

References 127 publications

(232 reference statements)

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“…The gradually increasing feature size with IEC was consistent with the trends observed for other ionomers. 23 The dimensions of ellipsoidal features also suggested that the calix-2 films likely had ∼20–80 layers of calix[4]arenes stacked within each spheroidal feature based on the calculation of the height of one calix[4]arene unit in a stack (∼1.0 nm). Such stacked arrangement can give rise to ionic conduction pathways with multiple length scales: (i) across individual calix[4]arene units of calix-2 (molecular-level ion channels), (ii) across overlapped/aligned macrocyclic units in a stack (connected ion channels), and (iii) along the surface of the upper rims of calix[4]arene units where the −SO 3 H groups are sitting side-by-side (lateral proton hopping along the chains).…”

Section: Resultsmentioning

confidence: 99%

“…While there have been significant efforts to design ionomers to improve the ionic conductivity of bulk membranes, 15 − 17 , 21 , 22 ionomers are rarely designed keeping in mind the specific issues associated with nanoscale confined thin films and with a target to improve thin-film ionic conductivity. 23 − 25 …”

Section: Introductionmentioning

confidence: 99%

“… 63 Lastly, but most importantly, we need good ionic conductivity in sub-micrometer-thick films to improve the interfacial ion transport behavior, a critical, but rarely addressed issue of hydrogen fuel cells, electrolyzers, and other electrochemical devices. 23 , 68 …”

Section: Introductionmentioning

confidence: 99%

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Molecular-Level Control over Ionic Conduction and Ionic Current Direction by Designing Macrocycle-Based Ionomers

Chatterjee

Zamani

Farzin

et al. 2022

JACS Au

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Poor ionic conductivity of the catalyst-binding, sub-micrometer-thick ionomer layers in energy conversion and storage devices is a huge challenge. However, ionomers are rarely designed keeping in mind the specific issues associated with nanoconfinement. Here, we designed nature-inspired ionomers (calix-2) having hollow, macrocyclic, calix[4]arene-based repeat units with precise, sub-nanometer diameter. In ≤100 nm-thick films, the in-plane proton conductivity of calix-2 was up to 8 times higher than the current benchmark ionomer Nafion at 85% relative humidity (RH), while it was 1–2 orders of magnitude higher than Nafion at 20–25% RH. Confocal laser scanning microscopy and other synthetic techniques allowed us to demonstrate the role of macrocyclic cavities in boosting the proton conductivity. The systematic self-assembly of calix-2 chains into ellipsoids in thin films was evidenced from atomic force microscopy and grazing incidence small-angle X-ray scattering measurements. Moreover, the likelihood of alignment and stacking of macrocyclic units, the presence of one-dimensional water wires across this macrocycle stacks, and thus the formation of long-range proton conduction pathways were suggested by atomistic simulations. We not only did see an unprecedented improvement in thin-film proton conductivity but also saw an improvement in proton conductivity of bulk membranes when calix-2 was added to the Nafion matrices. Nafion–calix-2 composite membranes also took advantage of the asymmetric charge distribution across calix[4]arene repeat units collectively and exhibited voltage-gating behavior. The inclusion of molecular macrocyclic cavities into the ionomer chemical structure can thus emerge as a promising design concept for highly efficient ion-conducting and ion-permselective materials for sustainable energy applications.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Molecular-Level Control over Ionic Conduction and Ionic Current Direction by Designing Macrocycle-Based Ionomers

Chatterjee

Zamani

Farzin

et al. 2022

JACS Au

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“…These studies are of high relevance to proton exchange membrane fuel cells in which the ion conduction limitation within a submicron thick ionomer (like Nafion, Figure a) layer at catalyst interface slows down the electrochemical reaction. , While the properties of bulk, free-standing, several tens of μm-thick ionomer membranes have been explored extensively, the understanding of ionomer thin films (<1 μm thick) is still inadequate. The continued efforts to unravel thin film behavior have made it evident that the proton conductivity − of submicron thick ionomer films are influenced in a complex manner by parameters such as hydrophilic–hydrophobic phase separation; − ionic domain size, , spacing, and connectivity; ,, water–ionomer mobility ,,, and orientation; ,, water–ionomer–substrate interfacial interactions; , and film stiffness. ,,,,, …”

mentioning

confidence: 99%

“…Fluorescent dyes have made an unprecedented improvement of our understanding of confined/nanoscopic systems by revealing (i) glass transition temperature, T g (pyrene-based dyes); − (ii) water diffusion coefficient, viscosity, − mobility, ,, and stiffness ,,,,, (rotor probes); (iii) proton transport dynamics, − proton concentration, ,, and ionic domain size (photoacid probes); and many other properties. Earlier, we incorporated a fluorescent photoacid probe HPTS (Figure b, top) within ionomer samples. ,, HPTS is sensitive to the local proton conduction environment and exhibits ratiometric fluorescence response ( I d / I P ).…”

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confidence: 99%

Unraveling Depth-Specific Ionic Conduction and Stiffness Behavior across Ionomer Thin Films and Bulk Membranes

2021

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Interfacial behavior of submicron thick polymer films critically controls the performance of electrochemical devices. We developed a robust, everyday-accessible, fluorescence confocal laser scanning microscopy (CLSM)-based strategy that can probe the distribution of mobility, ion conduction, and other properties across ionomer samples. When fluorescent photoacid probe 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) was incorporated into <1 μm thick Nafion films on substrates, the depth-profile images showed thickness- and interface-dependent proton conduction behavior. In these films, proton conduction was weak over a region next to substrate interface, then gradually increased until air interface at 88% RH. Conversely, consistently high proton conduction with no interface dependence was observed across 35–50 μm thick bulk, free-standing Nafion membranes. A hump-like mobility/stiffness distribution was observed across Nafion films containing mobility-sensitive probe (9-(2-carboxy-2-cyanovinyl)julolidine) (CCVJ). The proton conduction and mobility distribution were rationalized as a combinatorial effect of interfacial interaction, ionomer chain orientation, chain density, and ionic domain characteristics.

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Proton Exchange Membranes from Sulfonated Lignin Nanocomposites for Redox Flow Battery Applications

dos Santos,

McMichael,

Whitbeck

et al. 2024

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Redox flow batteries (RFBs) are increasingly being considered for a wide range of energy storage applications, and such devices rely on proton exchange membranes (PEMs) to function. PEMs are high‐cost, petroleum‐derived polymers that often possess limited durability, variable electrochemical performance, and are linked to discharge of perfluorinated compounds. Alternative PEMs that utilize biobased materials, including lignin and sulfonated lignin (SL), low‐cost byproducts of the wood pulping process, have struggled to balance electrochemical performance with dimensional stability. Herein, SL nanoparticles are demonstrated for use as a nature‐derived, ion‐conducting PEM material. SL nanoparticles (NanoSLs) can be synthesized for increased surface area, uniformity, and miscibility compared with macrosized lignin, improving proton conductivity. After addition of polyvinyl alcohol (PVOH) as a structural backbone, membranes with the highest NanoSL concentration demonstrated an ion exchange capacity of 1.26 meq g−1, above that of the commercial PEM Nafion 112 (0.98 meq g−1), along with a conductivity of 80.4 mS cm−1 in situ, above that of many biocomposite PEMs, and a coulombic efficiency (CE), energy efficiency (EE) and voltage efficiency (VE) of 91%, 68% and 78%, respectively at 20 mA cm−2. These nanocomposite PEMs demonstrate the potential for valorization of forest biomass waste streams for high value clean energy applications.

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Ionomers From Kraft Lignin for Renewable Energy Applications

Cited by 15 publications

References 127 publications

Molecular-Level Control over Ionic Conduction and Ionic Current Direction by Designing Macrocycle-Based Ionomers

Molecular-Level Control over Ionic Conduction and Ionic Current Direction by Designing Macrocycle-Based Ionomers

Unraveling Depth-Specific Ionic Conduction and Stiffness Behavior across Ionomer Thin Films and Bulk Membranes

Proton Exchange Membranes from Sulfonated Lignin Nanocomposites for Redox Flow Battery Applications

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