An oxygen-releasing device: Reversible oxygen release from a cobalt chelate-carbon composite in response to an applied voltage

A disk (e.g. diameter 2 cm × 2 mm) was made of [N,N′-bis(salicylidene)ethylenediamine]cobalt [Co(salen)] and carbon powder. The composite disk selectively absorbed oxygen from air, e.g. 22 cm³ oxygen per gram of composite at room temperature, which is almost stoichiometrically ascribed to 2:1 cobalt-dioxygen adduct formation. The adduct formation was an exothermic reaction, and the absorbed oxygen was released above 80°C. The application of 6 V to the disk sandwiched between platinum meshes induced a temperature elevation in the disk, which quickly released the absorbed oxygen. Under ambient conditions, the oxygen-releasing and -absorbing processes could be established within a few min and a 30 min interval, respectively, for the composite disk containing the 3-ethoxy derivative of Co(salen), while the oxygen absorption took several hours for the Co(salen) disk.