Study of Deuterium Isotope Separation by PEFC

Abstract

Hydrogen evolution and oxidation reactions were studied on a polycrystalline platinum electrode in 0.05 M D 2 SO 4 solution at 298 K by using a rotating disk electrode, focusing on the kinetic isotope effect on reactivity. The polarization measurements in the evolution reaction regime, on the one hand, revealed two Tafel regions: at low overpotentials close to the equilibrium potential, the Tafel slope was 0.039 V dec -1 , suggesting a Volmer-Tafel mechanism; and at potentials around 0.05 V or lower, a slope of 0.168 V dec -1 indicated that a transition to a Heyrovsky-Tafel mechanism occurred.In the oxidation reaction regime, on the other hand, a single Tafel slope of 0.055 V dec -1 was observed at potentials of 0.08 V or lower. Comparing between the deuterium and protium data for the kinetic factors supported the presence of an isotope effect, whereby the deuterium was more easily dissociated on the platinum electrode. The present kinetic result supported the deuterium separation of polymer electrolyte fuel cell (PEFC) in which the mixture gases of H 2 and D 2 were purged. The deuterium separation factor increased with increasing in the hydrogen utilization. This suggests a new isotope separation technique and also provides useful data for fuel cells.

Hydrogen isotope separation with an alkaline membrane fuel cell

“…Interestingly, the present result was smaller than the value of α reported for a PEFC system [8]. This might be explained because the systems produce water at different sites.…”

“…Such high catalytic activity might be attributed to the fuel cell's well-designed nanostructure. The same phenomenon was also reported when the fuel cell was operated with a cation exchange membrane (Nafion) [8]. This suggests that the exchange reaction depends on the catalyst rather than the membrane (H + or OH − type).…”

“…Less electricity was consumed by the separation process owing to the implementation of hydrogen energy recycling. More recent work has reported the hydrogen isotope effect during the anodic reaction in polymer electrolyte fuel cells (PEFCs) [8][9][10]. However, PEFCs require precious metal catalysts, rendering them expensive and unsuitable for use at the industrial scale.…”

Deuterium isotope separation by combined electrolysis fuel cell

“…The PEFC set up has been described in our previous paper [29], therefore, only the main points are mentioned here. Japan Automobile Research Institute (JARI) standard cell (FC Development Corp., Japan) was used.…”

“…To consider the full advantages of a CEFC system, it is necessary to investigate not only energy consumption but also the synergetic effects of additional separation in the fuel cell. It has been reported that the kinetic isotope effect of the hydrogen oxidation reaction is also been observed in PEFCs [28][29][30][31]. Hence, CEFCs have the potential to separate hydrogen isotopes more efficiently and cheaply than…”