Improving Sodium Solubility Recovery in the Hydrolysis Step of A Manganese-Oxide Solar Thermochemical Cycle for Renewable Hydrogen Production

Hydrogen has the potential to be used as an alternative energy carrier. A clean and renewable process for hydrogen production through water splitting is attained via a three-step manganese oxide solar thermochemical cycle. The only input to the cycle is water, and the net products of the cycle are hydrogen and oxygen; all other components are preserved. Hydrogen is produced by reacting MnO with NaOH. The resultant solid NaMnO2 product is hydrolyzed in an effort to recover the sodium, resulting in the solid products Mn2O3 and NaOH. In the final step, the Mn2O3 is reduced in a high temperature solar furnace back to the original MnO, thus completing the cycle. The hydrolysis step presents the biggest efficiency barrier, as only 90% of the sodium can currently be recovered using reasonable amounts of H2O. Mixed metal oxides have been synthesized in order to improve the sodium recovery in the hydrolysis step, thus improving the overall efficiency and feasibility of this thermochemical cycle. In the new proposed cycle, Zn or Fe ions are substituted into the manganese oxide and used in the above-mentioned cycle. This poster will present the results of using these mixed metal oxides to increase sodium recovery in the hydrolysis step.