Enhanced Durability of Polymer Electrolyte Membrane Fuel Cells by Functionalized 2D Boron Nitride Nanoflakes

Abstract

We report boron nitride nanoflakes (BNNFs), for the first time, as a nanofiller for polymer electrolyte membranes in fuel cells. Utilizing the intrinsic mechanical strength of two-dimensional (2D) BN, addition of BNNFs even at a marginal content (0.3 wt %) significantly improves mechanical stability of the most representative hydrocarbon-type (HC-type) polymer electrolyte membrane, namely sulfonated poly(ether ether ketone) (sPEEK), during substantial water uptake through repeated wet/dry cycles. For facile processing with BNNFs that frequently suffer from poor dispersion in most organic solvents, we non-covalently functionalized BNNFs with 1-pyrenesulfonic acid (PSA). Besides good dispersion, PSA supports efficient proton transport through its sulfonic functional groups. Compared to bare sPEEK, the composite membrane containing BNNF nanofiller exhibited far improved long-term durability originating from enhanced dimensional stability and diminished chronic edge failure. This study suggests that introduction of properly functionalized 2D BNNFs is an effective strategy in making various HC-type membranes sustainable without sacrificing their original adventurous properties in polymer electrolyte membrane fuel cells.

Recent advances in additive‐enhanced polymer electrolyte membrane properties in fuel cell applications: An overview

“…Sulfonic acid groups in polymers will form hydrogen bonds with bound water, leading to proton movement through hydronium ions formed through the hopping mechanism. Proton exchange capacity also depends on bound water . In addition to the bound water content, the uniformity of the nanofiller distribution in the polymer matrix also contributes to the good conductivity of the proton because it facilitates the movement of protons .…”

“…Proton exchange capacity also depends on bound water. 277 In addition to the bound water content, the uniformity of the nanofiller distribution in the polymer matrix also contributes to the good conductivity of the proton because it facilitates the movement of protons. 278 However, an excessively high nanofiller content does not promise good proton conductivity due to aggregation of functional groups.…”

Fouling resistant nanocomposite cation exchange membrane with enhanced power generation for reverse electrodialysis

“…5). The increase of IEC might be due to the reconstruction of the membrane micro and nanoscale structure, which increased the number of ion exchangeable functional groups for titration [58]. The decrease of IEC, which was observed in the 0.8 wt% O-MWCNT membrane, might be due to the aggregation of the O-MWCNTs inside the membrane matrices.…”

“…The ionic resistance of membranes decreased with the increase of O-MWCNT loading up to 0.5 wt%; however, the membrane ionic resistance abruptly increased with the further addition of nanomaterials. As the IEC increased, more functional groups were presented in the membrane matrices acting as ion exchange sites, which facilitated the ion transport; thus, the ionic resistance decreased [58]. Also, the addition of a proper amount of O-MWCNTs (r0.5 wt% in this case) favors the formation of continuous inner networks or connected ionic channels inside the nanocomposite CEM matrices [63], which made it easier for ion transport.…”

Interlocking Membrane/Catalyst Layer Interface for High Mechanical Robustness of Hydrocarbon‐Membrane‐Based Polymer Electrolyte Membrane Fuel Cells

“…The use of hydrocarbon (HC) ionomers in proton exchange membrane fuel cells (PEMFCs) as a membrane to replace the commonly used perfluorosulfonic acid (PFSA) ionomers has been widely explored in efforts to lower costs, raise fuel efficiency, and enable easier manufacturing of membrane/electrode assemblies (MEAs) . Examples include sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether sulfone) (SPAES), and sulfonated polyimide (SPI) . However, for the practical use of HC membranes for PEMFCs, attaining a tight interface between the HC membranes and the PFSA‐ionomer‐based catalyst layer (CL) to address the problem of interfacial delamination and consequent poor cell performance has proved challenging .…”