Separating hydrogen isotopes is a task of vast proportions. Over a thousand tons of heavy water (D2O) are produced every year to supply nuclear reactors worldwide as well as for medical and research applications. The production remains expensive for two reasons. First, the low natural abundance of deuterium (0.015%) implies that huge amounts of water should be processed (the industry standard for initial enrichment is 20% of D2O). Second, current technologies often need hundreds of stages to achieve the required degree of separation. This means that heavy-water plants are large even compared to many chemical plants. These issues result in high capital costs and large energy consumption. Indeed, producing 1 kg of enriched heavy water requires about 10 MWh , the annual energy consumption of a typical US household. Separating tritium—hydrogen’s heaviest isotope—is equally important and challenging, not least for its radioactivity. Nuclear reactors produce tritium during their operation, which has to be continuously removed to ensure optimum performance. Furthermore, experimental fusion facilities require tritium as a fuel, whereas accidents like the one at Fukushima Daiichi leave behind thousands of tons of diluted tritiated water. The current demand stimulates search for new separation technologies that could provide higher separation factors, reduce the number of stages and minimize the energy consumption.
It has recently been shown that perfect monolayers of graphene – impermeable to thermal atoms and molecules – are permeable to hydrogen nuclei. Moreover, the two-dimensional (2D) crystals could efficiently separate protons from deuterons. However, those studies used micron-size crystals obtained by exfoliation, a method unsuitable for industrial-scale applications. So the aim of this project is to explore the feasibility of graphene-based electrochemical pumps for industrial-scale separation of hydrogen isotopes.
