Large-scale floating polyacrylonitrile hybrid micro-/nanofiber membrane achieves efficient H/D isotope separation via photocatalytic proton transport

Advancements in isotope separation are both essential and challenging. The separation of water isotopes is vital in industrial production, biopharmaceuticals, and healthcare applications. This process is energy-intensive and complex due to the similarity of the isotopes. Pure polyacrylonitrile (PAN) is resistant to proton permeability, but neutral hydrogen radicals are capable of penetration. In this study, we report a novel approach using PAN macroscopic hybrid micro-/nanofibers in combination with a photocatalyst to separate hydrogen ion isotopes. Application of photocatalytic water splitting to generate protons results in significantly slower deuteron permeation in these fibers relative to protons, resulting in a separation factor of approximately 15 at room temperature. The composite PAN fibers exhibit a conductivity of 17.5 mS cm−1 at 25 °C and 95 % relative humidity. Our approach not only converts sunlight directly into storable hydrogen, but also enriches heavy water from H₂O/D₂O by H/D isotope separation. This study provides new insights into proton transport mechanisms in acidic media and demonstrates the significant potential of high molecular weight polymers for hydrogen isotope separation. [Display omitted] •The separation of hydrogen isotopes (separation factor: 15) was realized for the first time in heavy and light water using a functional PAN membrane. We have shown that the photocatalytic sieving effect of hydrogen isotopes is related to the zero-point oscillation effect.•The proposed Pt NC@CZS-GAF membranes transformed PAN into proton-conductive materials. Pt nanoclusters were introduced into the PAN matrix, allowing proton conductivity to reach 17.5 mS cm⁻1 at 25 °C and 95 % relative humidity. The membranes also exhibited a higher H₂ generation rate of 12.3 mmol‧m⁻2‧h⁻1 under visible light.•We propose that the coordination of N and Cd mediates electron transfer from the catalyst to PAN.