Scalable and efficient separation of hydrogen isotopes using graphene-based electrochemical pumping

M Lozada-Hidalgo,A K Geim,S Hu,I V Grigorieva,A Esfandiar,S Zhang

doi:10.1038/ncomms15215

M Lozada-Hidalgo, A K Geim + Show 4 more

Open Access

https://doi.org/10.1038/ncomms15215

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Abstract

Thousands of tons of isotopic mixtures are processed annually for heavy-water production and tritium decontamination. The existing technologies remain extremely energy intensive and require large capital investments. New approaches are needed to reduce the industry’s footprint. Recently, micrometre-size crystals of graphene are shown to act as efficient sieves for hydrogen isotopes pumped through graphene electrochemically. Here we report a fully-scalable approach, using graphene obtained by chemical vapour deposition, which allows a proton-deuteron separation factor of around 8, despite cracks and imperfections. The energy consumption is projected to be orders of magnitude smaller with respect to existing technologies. A membrane based on 30 m2 of graphene, a readily accessible amount, could provide a heavy-water output comparable to that of modern plants. Even higher efficiency is expected for tritium separation. With no fundamental obstacles for scaling up, the technology’s simplicity, efficiency and green credentials call for consideration by the nuclear and related industries.

Highlights

Thousands of tons of isotopic mixtures are processed annually for heavy-water production and tritium decontamination
Separating hydrogen isotopes is a task of vast proportions
Current technologies often need hundreds of stages to achieve the required degree of separation[2,4]. This means that heavy-water plants are large even compared to many chemical plants[2,3]. These issues result in high capital costs and large energy consumption[2,3]

Summary

Introduction

Thousands of tons of isotopic mixtures are processed annually for heavy-water production and tritium decontamination. Current technologies often need hundreds of stages to achieve the required degree of separation[2,4] This means that heavy-water plants are large even compared to many chemical plants[2,3]. The effective barrier is higher for deuterons than for protons because both are bound in their initial state to Nafion or water molecules, and zero-point oscillations at the hydrogen bond lift protons higher in energy than deuterons[12–14]. The current report explores the feasibility of graphene-based electrochemical pumps for industrial-scale separation of hydrogen isotopes. We suggest that this can be achieved by roll-to-roll[15] fabrication of large-area membranes that use standard CVD graphene supported on commercially available polymer films (Nafion[16])

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