Polarity Governed Selective Amplification of Through Plane Proton Shuttling in Proton Exchange Membrane Fuel Cell

Abstract

Graphene oxide (GO) anisotropically conducts protons with directional dominance of in plane ionic transport (σ IP) over the through plane (σ TP). In a typical H2-O2 fuel cell since the proton conduction occurs through the plane during its generation at the fuel electrode, it is indeed inevitable to selectively accelerate GO’s σ TP for its advancement towards a potential fuel cell membrane. We have successfully achieved ∼ 7 times selective amplification of GO’s σ TP by tuning the polarity of the dopant molecule in its nanoporous matrix. Coexistence of strongly non polar and polar domains in the dopant demonstrated a synergistic effect towards σ TP with the former decreasing the number of water molecules coordinated to protons by ∼3 times, diminishing the effects of electroosmotic drag exerted on ionic movements and the latter selectively accelerating σ TP across to catalytic layers by bridging the individual GO planes via extensive host guest H-bonding interactions. When they are decoupled, dopant with mainly non polar or polar features enhanced the σ TP only marginally revealing polarity factors contribute to fuel cell relvant transport properties of GO membranes only when they coexist. Fuel cell polarization and kinetic analysis reveal that such multi task dopants increased the fuel cell performance metrics of power and current densities by ∼ 3 times compared to pure GO membranes suggesting functional group factors of the dopants are of utmost importance in GO based proton exchange membrane fuel cells.