Kinetic study of the redox process for storing hydrogen: Reduction stage

The redox process, the reduction of metal oxides and subsequent oxidation by steam to release hydrogen, is an interesting alternative to other methods of storing hydrogen. In order to evaluate the suitability of different metallic oxides for this purpose, either alone (Fe2O3) or as mixed oxides (NiFe2O4, CuFe2O4), a kinetic study has been carried out by means of a thermogravimetric system. The kinetic parameters of the reduction of the oxides by hydrogen have been calculated by fitting experimental data with suitable “ad hoc” models for non-catalytic gas–solid reactions. The addition of a second metal to form double oxides has a positive effect, since these exhibit greater reaction rates.