Single-layer
graphene has been demonstrated to be a high-efficiency
hydrogen isotope sieving membrane in the electrochemical hydrogen
pumping system. In this work, we transferred this membrane to proton
exchange membrane water electrolysis (PEMWE), which has wide industrial
applications. Two membrane electrode assemblies with decorated Pt
and ink-coated Pt were investigated. The graphene with the decorated
Pt scheme acquired the reported highest proton-to-tritium separation
factor of 19.50 in PEMWE. However, rather than graphene, the decorated
catalyst was demonstrated to be responsible for this remarkable separation
efficiency. Previous studies from Geim’s group underestimated
the enhanced separation efficiency of decorated Pt over ink-coated
Pt, resulting in an exaggerated separation efficiency for graphene.
The behavior of proton transfer with hydrogen isotope separation through
graphene was interpreted by a serial-parallel circuit model, which
suggested that hydrogen isotope separation occurs at defect sites.
The limited separation efficiency for graphene was also well understood
by a density functional theory (DFT) calculation using an SW 55-77
model and the transition state theory for the kinetic isotope effect.
This research provides a thorough understanding of proton transfer
with hydrogen isotope separation through graphene.
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