Structure-Activity relationship of proton exchange membrane for nuclear wastewater under gamma radiation

Abstract

As the most widely used proton exchange membrane (Nafion), the impact of irradiation on the structure and properties of the membrane used in nuclear wastewater is a crucial focus of attention. This work investigates the structure–activity relationship of the wet Nafion under gamma irradiation. The membrane tensile strength decreased by 53.25 % and proton conductivity decreased by 50.96 % at 800 kGy. Long-term oxidation stability tests showed that the 600 kGy membrane could no longer be used after one cycle, with a 43.59 % decrease in electrical power and hydrogen permeation density of 37.78 mA/cm². The microstructure analysis shows that the membrane has not undergone chain breakage, but the molecular chain structure of the membrane has changed, increasing in free volume. Therefore, a novel structure–activity relationship was derived for the irradiation of membranes in aqueous environments, where wet membranes undergo co-swelling with radiation energy and water under gamma irradiation, increasing the free volume of the membrane structure. By combining theoretical simulations, different free volume models of membranes were constructed to verify the structure–activity relationship between mechanical properties, proton conductivity, hydrogen permeation performance, and free volume. This work provides a feasible structure–activity relationship for proton exchange membranes in nuclear wastewater under gamma radiation.