Manipulating Water in High-Performance Hydroxide Exchange Membrane Fuel Cells through Asymmetric Humidification and Wetproofing

Abstract

Hydroxide exchange membrane fuel cells (HEMFCs) are an emerging low-cost alternative to conventional proton exchange membrane fuel cells. In addition to producing water at the anode, HEMFCs consume water at the cathode, leading to distinctive water transport behavior. We report that gas diffusion layer (GDL) wetproofing strictly lowers cell performance, but that the penalty is much higher when the anode side is wetproofed compared to the cathode side. We attribute this penalty primarily to mass transport losses from anode flooding, suggesting that cathode humidification may be more beneficial than anode humidification for this device. GDLs with little or no wetproofing perform best, yielding a competitive peak power density of 737 mW cm −2 .

Beyond catalysis and membranes: visualizing and solving the challenge of electrode water accumulation and flooding in AEMFCs

“…Among these, water is particularly important in AEMFCs because of its severe intrinsic imbalance. 34,[40][41][42][43] In a PEMFC, water is only generated at the cathode at a rate of 2 water molecules for every 4 electrons transferred. In an AEMFC, there are 4 water molecules generated at the anode in addition to 2 water molecules consumed at the cathode for every 4 electrons transferred (Fig.…”

Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

“…However, many AEMs in the literature do not have the same efficient phase separation as Nafion ® and limited OH À conductivity (Table 1), which translates directly to low water backdiffusion rates [15,17]. Therefore, engineering solutions have been explored in a number of studies, including running commercial systems at very low current density [16], pressurizing the gas streams, or even feeding condensed water through the cathode [10] e none of which are tenable long-term solutions to high performing AEMFCs. Compared to many modern AEMs (Table 1), radiation-grafted ETFE-based AEMs have been reported to have high conductivity [13,18] and high water back diffusion rates [15,17], which may be utilized to alleviate the water gradient that is intrinsic to operating AEMFCs.…”

Quaternized poly(phenylene oxide) anion exchange membrane for alkaline direct methanol fuel cells in KOH‐free media

“…Since the ion transport will be from the cathode to anode, water is now produced at the anode and consumed at the cathode. Thus the water management regime is altered and potentially simplified; also the problem of flooding at the cathode is avoided …”