The commercialization of polymer electrolyte membrane fuel cells (PEMFCs), especially for heavy-duty vehicles with lifetimes exceeding one million miles, is hindered by the limited durability of the polymer electrolyte membrane (PEM). Nafion, a perfluorosulfonic acid (PFSA) membrane, is the benchmark for PEMFCs, offers excellent proton conductivity but undergoes chemical degradation due to reactive free radicals generated by gas crossover. This degradation damages the polymer chains, compromising membrane integrity and reducing overall stack performance. Addressing this challenge is key to advancing PEMFCs for long-term, large-scale applications. This dissertation addresses these durability concerns by investigating alternative membrane architectures aimed at overcoming the barriers to large-scale PEMFC commercialization. Specifically, graphene, with its exceptional gas barrier properties, is applied as a coating on PEMs to enhance chemical stability. Graphene's ability to block atom and molecule transport while allowing proton permeation is exploited in this work. Accelerated stress testing shows a 72% improvement in chemical stability for graphene-coated membranes compared to uncoated ones, attributed to the reduced gas crossover and free radical formation. Single-layer graphene coatings achieved a 20% reduction in gas crossover, while double-layer coatings reduced it by 55%, without significantly impacting membrane ionic resistance. However, challenges related to water management at high current densities were noted, warranting further investigation. Beyond membrane architecture, this dissertation investigates the understanding of potential decay during the OCV hold test. During OCV hold, an approximate 100 mV decay is observed in the first 24 hours. Significant recovery of this OCV loss has been achieved through the conventional “wet recovery process,” which involves lowering the cell potential under over-humidified conditions, confounding the effects of potential reduction and catalyst/ionomer reorganization due to humidification. This study introduces a novel “dry recovery protocol,” using 30% RH and applying 30 minutes of low potential hold in an H2/N2 environment followed by H2/Air. OCV recovery of 82%, 73%, 62%, and 58% was achieved at hold potentials of 0.13, 0.2, 0.6, and 0.8 V, respectively. The small changes in electrochemically active surface area and hydrogen crossover rate observed after 48 hours cannot fully explain the nearly 100 mV OCV drop, suggesting oxide coverage increases as the dominant factor for sharp OCV decay.