Abstract: Methods and systems for producing hydrogen and capturing carbon dioxide are disclosed. In some embodiments, the methods include the following: mixing magnesium bearing minerals with one or more acids and/or chelating agents to form a magnesium-rich solvent including magnesium hydroxide; mixing a gas including carbon dioxide with the magnesium-rich solvent in a reactor possibly in the presence of one or more water-gas shift catalysts; increasing a temperature and a steam pressure inside the reactor until a substantial portion of the magnesium hydroxide in the solvent and the carbon dioxide and water in the gas react to form magnesium carbonate and hydrogen; and increasing pH in the reactor thereby increasing a rate that the solvent and the carbon dioxide react.