Novel PEFC Application for Deuterium Isotope Separation

A Spontaneous Heavy Hydrogen Generator via a Protium Redox

The extreme significance of heavy hydrogen (D2) in medicinal, nuclear, and chemical sectors, despite its scarce natural abundance, underscores the vital imperative for inventing novel chemistries for its production. We showcase a spontaneous heavy hydrogen generator during commensurate electrical energy production by decoupling the direct chemistry of OD-/D+ dual ions via a protium redox. This exergonic electrochemistry yields ∼357 mL of D2 in nearly 85 h of continuous operation, with a commensurate electrical energy output of 122 kJ/per mole of D2. This laboratory-level demonstration of spontaneous heavy hydrogen production presents a novel chemistry for the scalable manufacture of nonprimordial D2.

A density functional theory (DFT) study on reduced partition function ratios of oxygen species adsorbed on a Pt19 cluster and oxygen isotope effects

A density functional theory (DFT) computation on oxygen species adsorbed on platinum (Pt) catalyst surfaces has been carried out to elucidate oxygen isotope fractionation observed at the cathode of a polymer electrolyte membrane fuel cell (PEMFC). The Pt(111) catalyst surface was modelled by a Pt₁₉ cluster, and O, OH, OHH, OO, OOH, OHOH and HOHOH were assumed to be the oxygen species adsorbed on the Pt(111) surface. The oxygen isotope reduced partition function ratios (RPFRs) of the adsorbed species were calculated using the vibrational frequencies obtained by normal mode analyses performed on the optimized structures. Various oxygen isotope exchange equilibria among the adsorbed oxygen species and oxygen and water molecules in the gas phase were examined using their RPFRs. Experimental observation that the lighter ¹⁶O is enriched in water molecules exhausted from the cathode is explainable in a satisfactory manner by assuming oxygen isotope exchange equilibria of O₂ molecule with O, OH, OO and OOH adsorbed on the Pt(111) surface that appear in the first half of the conversion reaction from O₂ to H₂O and those of H₂O molecule with the adsorbed oxygen species, OHH, OHOH and HOHOH, formed in the latter half of the conversion reaction.

Observation of 18O/16O isotope effects at the cathode of a polymer electrolyte membrane fuel cell

¹⁸O/¹⁶O isotope effects were observed at the cathode of a polymer electrolyte membrane fuel cell at 25 and 35°C. Results of experiments in which the ¹⁸O/¹⁶O isotope ratios of the oxygen gases supplied to and exhausted from the cell were measured revealed that the lighter isotope ¹⁶O reacted more preferentially to form water molecules at the cathode than the heavier one, ¹⁸O. The value of the oxygen isotope separation factor, S₁, defined as the ratio of the ¹⁸O/¹⁶O isotope ratios of the oxygen gases supplied to and exhausted from the cell, ranged from 1.0030 to 1.0139, and tended to decrease with decreasing rate of oxygen utilisation (θ) and with increasing flow rate of the feed oxygen gas (D_F). The value of another separation factor, S₂, defined as the ratio of the ¹⁸O/¹⁶O isotope ratios of the exhausted oxygen gas and oxygen having reacted to form water molecules at the cathode, ranged from 1.0049 to 1.0304. The S₂ value was much less affected by the change in θ and D_F than the S₁ value with the majority of the S₂ value being in the range of 1.0240-1.0304.