While screening thermochemical cycles we determined that the cadmium carbonate cycle has the potential of producing hydrogen at very high efficiency using high temperature solar thermal energy.  The cycle consists of three chemical reactions:

                                           Cd(s) + CO₂(g) + H₂O(l) => CdCO₃(s)            T < 300^oC,

                                                    CdCO₃(s) => CdO(s) + CO₂(g)                     T ~ 500^oC,

                                                        CdO(s) => Cd(g) + ½ O₂(g)                       T > 1400^oC.

The results are presented on an experimental program aimed at accelerating the rate of the hydrogen production reaction.  A flowsheet is presented for the overall process and the cost of hydrogen is estimated.