Towards Sustainable Proton Exchange Membranes: Materials and Challenges for Water Electrolysis

This article provides a comparative analysis of sustainable polymer membranes based on biopolymers and Nafion in the context of proton exchange membrane (PEM) for water electrolyzers. Nafion, a perfluorinated polymer, has been a standard choice for PEM applications due to its excellent proton conductivity and chemical stability. However, the sustainability challenges associated with its production, lifecycle and cost necessitate the exploration of alternative materials that may offer comparable performance while being environmentally friendly. The most promising alternative polymer for PEM electrolyzers appears to be cellulose with good thermal stability at 200 °C and a water absorption of 35%, which is slightly higher compared to Nafion membranes with a water absorption value of around 30%. Sustainable PEMs also have much lower hydrogen permeability, e.g., chitosan has been determined to have a permeability of 7 barrers, while Nafion is characterized by a value of more than 100 barrers. The biggest drawbacks of sustainable membranes are proton conductivity and durability, where Nafion membranes are still superior. This review also focuses on mechanical properties, chemical resistance, preparation methods and cost-effectiveness. Sustainable polymers show promising properties for supporting efficient hydrogen production, especially in dynamic operating environments facilitated by renewable energy sources.