Studies on Electrochemical Hydrogen Isotope Separation

Graphene-integrated Proton Exchange Membrane (PEM) electrochemical cells have emerged as a novel area of scientific investigation in the realm of hydrogen isotope separation. Chemical Vapor Deposited (CVD) graphene has been especially useful due to its large-scale production capability for scaling-up purposes. The research described in this dissertation explores the role that inadvertent introduction of cations, notably ammonium and copper, during the CVD graphene transfer onto PEM substrates, such as Nafion, might play in affecting hydrogen ion transport and isotope separation in PEM electrochemical cells. An extensive review of existing literature exposed a gap concerning unintentional cation introductions during graphene transfer, and this research posits that observations of apparent isotope separation could be attributable to effects from ammonium or copper cations in the membranes. Central to these studies is the elucidation of the challenges in reproducing optimal H/D selectivities, attributed to methodological inconsistencies. Seeking deeper insights, this study tapped into the capabilities of the Online Electrochemistry Mass Spectrometry (OEMS) system. Rather than relying on comparative studies in separate H and D electrochemical pump cells, the OEMS facilitated time-dependent studies of evolved gases in electrochemical pump cells, allowing for the direct analysis of true isotope separation from gas mixtures. Employing techniques to directly probe H/D separation, this dissertation identifies a minimal impact of graphene on this process. This investigation aligns with other recent works that question established beliefs regarding CVD graphene\u27s pronounced impact on hydrogen isotope separation