Self-Humidifying Proton Exchange Membranes for Fuel Cell Applications: Advances and Challenges

Abstract

Polymer electrolyte fuel cells (PEFCs) provide efficient and carbon-free power by converting the hydrogen chemical energy. The PEFCs can reach their greatest performance in humidified condition, as proton exchange membranes (PEMs) should be humidified for their proton transportation function. Thus, external humidifiers are commonly employed to increase the water content of reactants. However, being burdened with external humidifiers can make the control of PEFCs complicated and costly, in particular for transportation application. To overcome this issue, self-humidifying PEMs have been introduced, with which PEFC can be fed by dry reactants. In fact, internal humidification is accomplished by produced water from the recombination of permeated hydrogen and oxygen gases on the incorporated platinum catalysts within the PEM. While the water production agent remains constant, there is a broad range of additives that are utilized to retain the generated water and facilitate the proton conduction path in the PEM. This review paper has classified the aforementioned additives in three categories: inorganic materials, proton-conductive materials, and carbon-based additives. Moreover, synthesis methods, preparation procedures, and characterization tests are overviewed. Eventually, self-humidifying PEMs endowed with platinum and different additives are compared from performance and stability perspectives, such as water uptake, proton conductivity, fuel cell performance, gas cross-over, and the overall durability. In addition, their challenges and possible solutions are reviewed. Considering the concerns regarding the long-term durability of such PEMs, it seems that further investigations can be beneficial to confirm their reliability for prolonged PEFC operation.

Numerical investigation of gas cross‐over and hydrogen peroxide formation in hydrocarbon‐based fuel cell membranes

“…Obviously, gas cross‐over is a function of membrane thickness and employing thinner membranes would exacerbate the permeability problem, despite promising improvements in performance 16,47 . The impact of membrane thickness on gas cross‐over is also indicated in Figure 5A‐C.…”

“…Obviously, gas cross-over is a function of membrane thickness and employing thinner membranes would exacerbate the permeability problem, despite promising improvements in performance. 16,47 The impact of membrane thickness on gas cross-over is also indicated in Figure 5A-C. A 50% reduction in thickness has led to an approximately 90% rise in hydrogen and oxygen crossover rate through the SPEEK membrane.…”

Promising Membrane for Polymer Electrolyte Fuel Cells Shows Remarkable Proton Conduction over Wide Temperature and Humidity Ranges

“…The thickness of the cast Nafion membrane was 35 μM. The membranes were cast as thin as possible to facilitate the water back-diffusion from the cathode to the anode during fuel cell operation under low humidity operation conditions while keeping the low level of hydrogen crossover. , The prepared membranes were labeled Naf/BiPyPBI-0.1, Naf/BiPyPBI-0.25, Naf/BiPyPBI-0.5, and Naf/BiPyPBI-0.75.…”

Functionalized and Biomimicked Carbon-Based Materials and Their Impact for Improving Surface Coatings for Protection and Functionality: Insights and Technological Trends

“…There are several strategies to maintain cleanliness on surfaces, which include surfaces with self-cleaning properties, biomimetic structural design, and the use of biocidal chemical mediators to deter fouling. Amphiphilic modified surfaces are also a recent development [90,91]. An antistick coating agent based on carbon is a promising option.…”