Electrode-level Water Management Strategies for Anion Exchange Membrane Fuel Cells

Abstract

Anion exchange membrane fuel cells (AEMFCs) have emerged as a promising alternative to commercialized proton exchange membrane fuel cells because they can enable much lower costs by using cheaper materials, especially non-precious metal electrocatalysts. However, the commercialization of AEMFCs faces several technical challenges, including water management during operation. More specifically, achieving high power density typically requires AEMFCs to be operated with anode/cathode reacting gas dew points much lower than the cell operating temperature to prevent flooding. Conversely, achieving long lifetime typically requires reacting gases with high relative humidities to be supplied to the cell. A solution is needed that can allow for high power density to be achieved under states of high hydration – i.e., high reacting gas dew points, even at lower operating temperatures (e.g., 60°C). This work explores multiple electrode-level water management strategies for AEMFCs with the goal of enabling high power operation at high states of hydration, including: i) hydrophobic catalyst layers by adding PTFE; ii) hydrophilic catalyst layers by adding Nafion®; iii) gas diffusion layers (GDLs) with patterned wettability; and iv) combinations thereof. Compared to hydrophobic electrodes suffering serious flooding at high hydration states, the promising result of this work is one of the highest reported peak power densities reported to date, 1.5 W cm^-2, under H₂/O₂ flow with hydrophilic-hydrophobic hybrid electrodes, even with anode and cathode dew points of 59 °C and 62 °C, respectively. It is expected that these electrode-level water management strategies can contribute to the commercialization of AEMFCs in the near future.