We systematically studied the catalytic activity of the oxygen evolution reaction (OER) for the tetragonal spinel oxide Mn3-xCoxO4 (0 ≤ x < 1 and 1 < x ≤ 1.5). The OER catalytic activity of Mn3-xCoxO4 (0 ≤ x < 1) dramatically improved with an increase in Co content. We found that the OER activity of Mn3-xCoxO4 (0 ≤ x < 1) increased linearly with the suppression of the Jahn-Teller distortion. We therefore propose that the Jahn-Teller distortion plays an important role in the OER activities of compounds containing Mn 3+ . Mn3-xCoxO4 (0 ≤ x < 1) provides a rare case for directly studying the effect of the Jahn-Teller distortion on OER activity.

Sr2VFeAsO3−δ remarkably enhances the oxygen evolution reaction by direct O–O bond formation between OH− coupled oxygen-vacant sites.

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We conducted in situ angle dispersive high pressure x-ray diffraction experiments on Sr3Ir2O7 up to 23.1 GPa at 25 K with neon as the pressure transmitting medium. Pressure induces a highly anisotropic compressional behavior seen where the tetragonal plane is compressed much faster than the perpendicular direction. By analyzing different aspects of the diffraction data, a second-order structural transition is observed at approximately 14 GPa, which is accompanied by the insulating state to nearly metallic state at 13.2 GPa observed previously (Li et al 2013 Phys. Rev. B 87 235127). Our results highlight the coupling between electronic state and lattice structure in Sr3Ir2O7 under pressure.

A tetragonal perovskite PbMnO(3) was obtained by treating the 6H hexagonal perovskite phase at 15 GPa and 1273 K. Structural analysis using synchrotron X-ray diffraction suggested that PbMnO(3) crystallizes in the centrosymmetric space group P4/mmm, unlike PbTiO(3) and PbVO(3) which have a polar structure in space group P4mm. Iodometric titration revealed the presence of the oxygen deficiency of x = 0.06 for PbMnO(3-x). The hexagonal 6H and the 3C perovskite phases exhibited antiferromagnetic ordering at 155 and 20 K, respectively.