(511f) Solar Decomposition Of Manganese Oxide To Split Water

A three-step metal oxide cycle to produce renewable hydrogen has been proposed. This cycle employs manganese oxide and solar energy to produce hydrogen:

½Mn₂O₃ → MnO + ¼O₂ (1)

MnO + NaOH → ½H₂ + NaMnO₂ (2)

NaMnO₂ + ½H₂O → ½Mn₂O₃ + NaOH (3)

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H₂O → H₂ + ½O₂ (4)

Most work on the manganese oxide cycle has focused on the hydrogen generating step (Equation 2) and the product recovery step (Equation 3) with little work done on the reduction step (Equation 1). It is essential to understand the reduction step because the entire feasibility of the manganese oxide cycle is based on this reaction having a high overall conversion. Specifically, the viability of the MnO and O₂ phase separation must be investigated to determine how much recombination might occur during the quench step. Because of the importance of the reduction step, a kinetic study in an Aerosol Flow Reactor (AFR) has been done, as it can handle a high throughput of powder, while allowing reaction conditions to be tightly controlled. In addition, to the kinetic study in the AFR, a mechanistic study has been performed in a Thermogravimetric Analyzer. This poster will highlight results from these studies.