Molecular‐Level Hybridization of Nafion with Quantum Dots for Highly Enhanced Proton Conduction

Abstract

Nanophase-separated membranes hold promise for fast molecule or ion transfer. However, development and practical application are significantly hindered by both the difficulty of chemical modification and nanophase instability. This can be addressed by organic-inorganic hybridization of functional fillers with a precise distribution in specific nanophase. Here, a molecular-level hybridization for nanophase-separated Nafion using 2-5 nm quantum dots (QDs) as a new smart filler is demonstrated. Two kinds of QDs are prepared and used: hydrophilic polymer-like QDs (PQDs) and hydrophobic graphene oxide QDs (GQDs). Because of selective interactions, QDs offer advantages of matched structural size and automatic recognition with the nanophase. A distinctive synthesis of subordinate-assembly, in which QDs are driven by the self-assembly of Nafion affinity chains, is reported. This results in a precise distribution of QDs in the ionic, or backbone, nanophases of Nafion. The resulting PQDs in the ionic nanophase significantly increase membrane proton conduction and device output-power without loss of mechanical stability. This is difficult to realize with conventional fillers. The GQDs in the backbone nanophase reduce the crystallinity and significantly augment membrane water uptake and swelling capacities.

Improved chemical stability and proton selectivity of semi‐interpenetrating polymer network amphoteric membrane for vanadium redox flow battery application

“…47 On the other hand, the protons can be transported through extra hoping sites between the N atoms and sulfonic groups in a shortened distance. 48 Crossovers of vanadium ion through the IEM will result in low energy efficiency, which limit the application of membranes in VRFB. In order to estimate the vanadium resistance of various membranes, the VO 2+ permeability value is presented in Figure 7(a).…”

Surface Enriched Sulfonic Acid Ionic Clusters of Nafion Nanofibers as Long‐Range Interconnected Ionic Nanochannels for Anisotropic Proton Transportation: Phenomenon and Molecular Mechanism

“…The concentration of the methanol in Cell B was monitored by a Trace‐1300 gas chromatograph. The methanol permeability was calculated as follows: [ 21 ] where A , L , and V B are the effective area, the thickness of the membrane, and the volume of Cell B, respectively. C A and C B are the concentrations of methanol solution in Cell A and Cell B, respectively.…”

“…[ 14,20 ] The manufacture of high‐density sulfonic acid group ionic clusters and formation into a long‐range interconnected proton exchange ionic nanochannels is the key to further enhancing the performance of the NF‐based PEMs. [ 21,23 ]…”

Graphene‐Based Advanced Membrane Applications in Organic Solvent Nanofiltration

“…In particular, graphene‐based membranes have demonstrated their superiority owing to their high stability in organic solvents. In addition, graphene‐based materials have been widely applied in several well‐known fields, including gas (and liquid) adsorption and separation, [ 60–63 ] plastic electronics, [ 64–67 ] solar cells, [ 68,69 ] lithium ion batteries, [ 70–72 ] supercapacitors, [ 73–79 ] electrocatalysis, [ 80–82 ] optics, [ 83 ] and biosensors. [ 84–86 ] Therefore, in this paper, the structural properties of graphene and its derivatives are elaborated, followed by a discussion on the common characterizations that are critical in evaluating the membrane performance.…”