Fluorine-Free Ion Exchange Membranes for (Photo)electrochemical Applications.

The increasing global demand for sustainable energy solutions has driven significant advancements in photoelectrochemical (PEC) technologies, particularly for hydrogen production and biomass valorization. A key challenge for PEC cells is the selection of ion exchange membranes (IEMs) that ensure efficient product separation between anode and cathode half-cells while enabling efficient ion transport. Moreover, these membranes also need to show long-term stability. Traditionally, perfluorinated membranes such as Nafion have been widely used due to their high proton conductivity and chemical resilience. However, their high cost, environmental concerns, and the impending regulatory restrictions on per- and polyfluoroalkyl substances necessitate the development of fluorine-free alternatives. This review explores the latest advancements in fluorine-free IEMs for (photo)-electrochemical applications, highlighting their synthesis, physicochemical properties, appropriate characterization methods, and performance metrics. We discuss emerging materials that offer comparable ionic conductivity, durability, and operational efficiency while addressing recyclability and environmental impact. By assessing the potential of these next-generation membranes, we aim to provide insights into their role in advancing photo- and electrochemical systems toward a more sustainable and economically viable future.