Hydrogen can be produced using a renewable manganese oxide base water splitting cycle. This cycle has three reactions steps:
½Mn2O3→ MnO + ¼ O2ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý (1)
MnO + NaOH → ½ H2Ìý+ NaMnO2ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý(2)
NaMnO2Ìý+ ½ H2O → ½ Mn2O3Ìý+ NaOHÌýÌýÌý ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý(3)
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H2O → H2Ìý+ ½ O2 Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý Ìý (4)
The third step of this cycle is the hydrolysis of NaMnO2Ìýused to recover sodium hydroxide and Mn2O3. The second reaction has a tendency to form a birnessite type of sodium manganese oxide. Birnessite traps sodium in the manganese oxide crystal phase preventing complete hydrolysis and requires the addition of excess water to the third reaction step, which significantly decreases the overall cycle efficiency [1]. On average, Ìý10% birnessite NaMnO2Ìýwill enter the high temperature solar reaction step with a potential of forming highly reactive and corrosive gases such as Na2O [2]. The main goal of my research is to investigate various ways of improving the efficiency of the manganese oxide hydrolysis step while reducing the amount of birnessite sodium manganese oxide carried through the cycle.