Core Size-Dependent Proton Conductivity of Silica Filler-Functionalized Polymer Electrolyte Membrane

Abstract

Polymer electrolyte fuel cells (PEFC) are expected as next energy generation systems, and their performance is strongly dependent upon the polymer electrolyte membrane (PEM). We have suggested a new model of PEM with a three-dimensional proton conduction passways structure using the filler method, particularly focused on the functionalization of filler particles. The polymer surface-functionalized silica nanoparticles (NPs) with three different particle sizes were prepared by the reversible addition–fragmentation chain transfer polymerization with particles (RAFT PwP) method that we developed. Silica NPs coated with an in situ polymerized block copolymer consisted of a proton conductive polymer and a protective polymer. We confirmed that the proton conductivity increased and the activation energy decreased as the core particle size became smaller because of enlarging the total interface area between each particle and increasing the proton conduction passways.

Effect of Surface Silanol Density on the Proton Conductivity of Polymer-Surface-Functionalized Silica Nanoparticles

“…These small activation energies suggest that the proton conduction of each sample undergoes hopping through hydrogen-bonding network (Grotthuss mechanism). This is the same as our previous study. ,, …”

“…According to our previous work, silica@PAA- b -PS using silica NPs with a particle size of 200 nm showed a proton conductivity of 1.22 × 10 –4 S/cm with a small activation energy of 0.20 eV at 60 °C and 98% relative humidity (RH). This small activation energy (<0.4 eV) indicates that the proton conduction in silica@PAA- b -PS undergoes with the Grotthuss mechanism (proton hopping via hydrogen bonding). , Furthermore, we have recently clarified the dependence of core size and PAA coverage on the proton conduction performance of silica@PAA- b -PS. , …”

Recent Advancements in Polysulfone Based Membranes for Fuel Cell (PEMFCs, DMFCs and AMFCs) Applications: A Critical Review

“…In practice, this approach is commonly applied in order to modify the characteristics of a virgin macromolecule, attaining superior properties in the resulting blended materials [88][89][90][91]. (ii) The preparation of composite membranes by dispersion of inorganic fillers including silica (SiO2) [92], titania (TiO2) [93], zeolites [94], and heteropoly acids inside the polymer matrix have been demonstrated to satisfactorily enhance the ionic conductivity of the resulting electrolyte without sacrificing its mechanical resistance [95,96]; and (iii) the introduction of functionalized 2D-layered materials (example, graphene oxide, smectite clay, layered double hydroxides (LDHs), and siliceous layered materials) effectively lowers the methanol permeability in Nafion-based membranes and simultaneously improves their proton conductivity, water retention capacity, and thermo-mechanical resistance [97][98][99][100]. Among these inorganic fillers, LDHs have recently gained more attention, a class of nanostructured materials belonging to the anionic clay family, with unique physicochemical properties [101][102][103][104].…”

Emerging Applications of Silica Nanoparticles as Multifunctional Modifiers for High Performance Polyester Composites

“…Grafting polymers onto SNs is another effective way to improve interfacial interactions in nanocomposites [134]. Generally, there are two main approaches to chemically attaching polymer chains to the surface of SNs.…”