Exploration of heterogeneous catalyst for molecular hydrogen ortho-para conversion

The catalysts for nuclear spin conversion of molecular hydrogen (ortho-para H2 conversion), are categorized into four groups in the ascending order of activity at 77 K; Group 1: metallic materials and most of the oxides containing low-valence metal cations; Groups 2 and 3: metal oxides comprising high-valence cations; Group 4: metal oxides and hydroxides that consist of magnetic metal cations.


Molecular hydrogen (H2) ortho-para conversion (O/P conversion) proceeds slowly at low temperatures accompanying a heat release. Thus, catalysts for accelerating this conversion rate are highly demanded in terms of the storage and utilization of liquid H2. The catalysts for this purpose are experimentally screened by examining a broad range of materials covering magnetic, non-magnetic, metallic, and nonmetallic oxides. The primary conclusions obtained are summarized below. (1) active materials are required to be non-metallic and to bear the cations with ionic radii smaller than the bond length of H2. (2) Metallic materials have almost no activity irrespective of with or without magnetism (3) The activity of materials belonging to (1) is largely enhanced when the constituting cation has a magnetic moment. In addition, there is a class of materials for which the activity is distinctly enhanced just upon substitution by the foreign ions.

Author list:

Hideki Abe*, Hiroshi Mizoguchi, Ryuto Eguchi, Hideo Hosono*

How to cite:

H. Abe, H. Mizoguchi, R. Eguchi, H. Hosono, Exploration 2023, 20230040.