Nanocrystalline Boron Nitride Coating for High Conductivity, Low Temperature Proton Exchange Membrane Fuel Cells

Abstract

Hydrogen fuel cells based on proton exchange membrane (PEM) technology are promising as an alternative to fossil fuel-based energy. Conventional PEMFC technology is operated at fully humidified conditions in a narrow temperature range (~ 80 oC) to maintain sufficient proton conductivity and power output, which necessitates high cost of operation. In this work, we demonstrate a scalable, room temperature coating of ultrathin boron nitride (BN) via pulsed laser deposition (PLD) that simultaneously increases conductivity of perfluorosulfonic acid (PFSA) based membranes while decreasing the crossover. Remarkably, BN coated membranes show a 20% increase in performance at current operational conditions (1.485 A/cm2 @ 0.6 V) and a 20% increase in power density (0.965 W/cm2) while exhibiting a maximum crossover current decrease of 32% (3.58 mA/cm2) relative to industry standard Nafion™ 211. Furthermore, we demonstrate a reduction of operational temperatures to as low as 60 oC with modified membranes without performance impact, thereby affording substantial reduction of the PEMFC operational cost. These observations are practically relevant for the development of next generation PEM technology by enabling more scalable and cost-effective high performance fuel cell stacks.