P2-7762 Types of Hydrogen: for Effective Storage of Liquid HydrogenKey Words:Hydrogen, Storage, Ortho-Para conversion, Catalysts Hydrogen (H2) exists in two nuclear-spin isomers: ortho-hydrogen and para-hydrogen. Their interconversion plays a crucial role in the efficient storage of liquid hydrogen, as the slow spontaneous conversion from ortho to para releases heat and causes boil-off losses Max 55% losses). To overcome this challenge, catalytic promotion of ortho–para conversion before liquification is essential.⚫Metal catalysts showed almost no activity.⚫Mixed-valence oxides exhibited strong catalytic performance.⚫A possible correlation with cation size was observed.⚫The reaction may be promoted by local electric fields.ConclusionMethodologyNew set up for practical O/P conversion⚫Design of catalysts that enhance the local electric field⚫Defect engineering for controlled charge distribution⚫Development of practical catalysts for real-world applicationsFuture PlanIntroduction•A comprehensive screening approach led to the discovery of a series of promising catalysts.•Most metals showed negligible activity.•Materials with intrinsic mixed valence states and structural defects emerged as highly active.Theme underDiscussionCatalyst Screening ResultsOperation Test (Conventional FeOxHy)•System operation was confirmed, consistent with the thermodynamic equilibrium curve of ortho-and para-hydrogen.•Successfully achieved complete O/P conversion at 30 K.•A closed system apparatus was employed for the experiment.•The catalyst was cooled to 77 K using liquid nitrogen.•Hydrogen gas was circulated through the system using a plunger pump, and the time-dependent composition was analyzed.•The ortho–para hydrogen ratio was determined by Raman spectroscopy.•Measurement range: 3–400 K•Practical catalytic activity observed near the L-hydrogen temp (~20 K)Hydrogen Production Catalyst Material Group, GREEN Shusaku Shoji, Hideki Abe,＊＊ Hiroshi Mizoguchi, Ryuto Eguchi, Hideo Hosono E-mail：： Shoji.shusaku@nims.go.jp, Abe.Hideki@nims.go.jp00.20.40.60.811.21.4Rate constant of O/P conversion (/hr)•Mn3O4,CeO2, Co oxide systems showed high activity00.511.522.53050100150200250300O/P ratioTemperature(K)200300400500600700Wave number(cm-1)Intensity (a.u.)OrthoParaRT30K
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