Proton incorporations and superconductivity in a cobalt oxyhydrate

We report evidence of proton incorporations in a newly-discovered cobalt oxyhydrate superconductor. During the hydration process for Na0.32CoO2 by the direct reaction with liquid water, it was shown that substantial NaOH was gradually liberated, indicating that H+ is incorporated into the hydrated compound. Combined with the thermogravimetric analysis, the chemical composition of the typical sample is Na0.22H0.1CoO2·0.85H2O. It shows bulk superconductivity at 4.4 K.