The heavy isotopes of hydrogen, deuterium (D) and tritium (T) are materially important in nuclear energy production. In current heavy-water nuclear fission reactors, D is used as a neutron-moderator. Similarly, in nuclear fusion reactors, which are expected to represent the next generation of nuclear power, the reaction of D and T is responsible for the energy production stage.

Many researchers have studied various isotope-separation methods, including water distillation, chemical exchange, water electrolysis and combined electrolysis catalytic exchange (CECE). The electrolysis method yields the most effective separation but the process consumes enormous amounts of electricity. This has led to a search for other methods that are more energetically efficient.

In an attempt to solve the above problem, we proposed a new concept of hydrogen separation system: the Combined Electrolysis Fuel Cell (CEFC) process [1]. Here, hydrogen and oxygen were produced by electrolysis and used for power generation by fuel cells. Less electricity was consumed by the separation process owing to the implementation of hydrogen energy recycling. More recent works have reported the hydrogen isotope effect in polymer electrolyte fuel cells (PEFCs) [2, 3].

We found that CEFC could reduce 20 % electric energy, comparing with the only electric separation process. Furthermore, CEFC showed the high separation factor (α ≃10) due to the synergistic effect of PEFC and water electrolysis. Here, we will discuss the separation efficiency and the calculation of the total energy consumption by CEFC in several electrolytic and FC conditions.

REFERENCES

[1] H. Matsushima et al., Energy, 30 (2005) 2413.

[2] R. Ogawa et al., Electrochemistry Communications, 70 (2016) 5.

[3] S. Shibuya et al., Journal of The Electrochemical Society, 163 (2016) F704