Hydrophilicity-Regulated Graded Interfacial Engineering for Anion Exchange Membrane Fuel Cells

Abstract The insufficient durability of anion exchange membrane fuel cells (AEMFCs) remains a major barrier to their practical application. Water management is one of the critical factors governing AEMFC performance and durability. Insufficient hydration at the cathode catalyst layer and the membrane interface is considered to mainly restrict the durability of AEMFCs. To address this limitation, a super hydrophilic ionomer coating was directly introduced onto the membrane surface to construct a hydrophilicity-regulated, locally water-retentive interfacial region. Benefiting from the high water uptake of QPCBP-10 (381% at 20 °C and 451% at 90 °C), the coating formed a locally water-retentive gradient region at the cathode catalyst layer and the membrane interface, building up a good reaction micro-environment. The coating loading was optimized to balance interfacial humidification, kinetic polarization, and mass-transport polarization, with an optimal loading of 0.155 mg cm−2. During the durability testing at 300 mA cm−2 and 80 °C, the coated membrane electrode assembly (MEA) showed a voltage decay rate of 3.69 mV h−1, compared with 8.17 mV h−1 for the uncoated baseline MEA, corresponding to a 55% reduction. The time-normalized charge-transfer-resistance growth rate decreased from 0.0477 to 0.0187 Ω cm2 h−1. This work provides a targeted hydrophilicity-regulated interfacial engineering strategy for localized water management and improved operational durability of AEMFCs.