Abstract
The effects of temperature on hydrogen (H2) production in the alteration of olivine [(Mg,Fe)2SiO4] have been investigated under both CO2-rich (0.5 mol/L NaHCO3) and CO2-free conditions at 225–300 °C. Under CO2-rich conditions, H2 production rates showed strong temperature dependence, where the rate drastically increased for ≥275 °C, while the rate in CO2-free conditions was less temperature-dependent. At 300 °C under CO2-rich conditions, the H2 generation rate was 3 times faster than that under CO2-free conditions, and a considerable amount of CO2 was simultaneously stored as magnesite [(Mg,Fe)CO3]. Increasing the temperature under CO2-rich conditions promoted olivine consumption, while suppressing both brucite [(Mg,Fe)(OH)2] formation and incorporation of Fe(II) into secondary minerals, thus facilitating Fe(II) release and oxidation to produce H2. It has been revealed for the first time that H2 production during water-olivine-CO2 reactions is markedly accelerated via high-temperature-facilitated Fe(II) release.
Published Version
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