Methods and systems for making calcium oxide (CaO), carbon dioxide (CO.sub.2) and/or calcium hydroxide (Ca(OH).sub.2) from aragonite, for example, oolitic aragonite, are provided. The method can include applying solar energy, for example, by focusing one or more mirrors in one or more heliostats, to heat a reactant mixture in a vessel. The reactant mixture includes oolitic aragonite and can be heated to a temperature from 500° C. to 950° C. The system can include a vessel and a means for applying solar energy to heat a supply of oolitic aragonite disposed inside the vessel. Methods of converting the CO.sub.2 to ethanol, ethylene, graphene, and/or methane are also provided.

One variation of a method includes: ingesting an air sample captured during an air capture period at a target location for collection of a first mixture including carbon dioxide and a first concentration of impurities; conveying the first mixture through a liquefaction unit to generate a second mixture including carbon dioxide and a second concentration of impurities less than the first concentration of impurities; in a methanation reactor, mixing the second mixture with hydrogen to generate a first hydrocarbon mixture comprising a third concentration of impurities comprising nitrogen, carbon dioxide, and hydrogen; conveying the first hydrocarbon mixture through a separation unit configured to remove impurities from the first hydrocarbon mixture to generate a second hydrocarbon a fourth concentration of impurities less than the third concentration of impurities; and depositing the second hydrocarbon mixture in a diamond reactor containing a set of diamond seeds to generate a first set of diamonds.

Disclosed herein are carbon doped tin disulphide (C—SnS.sub.2) and other SnS.sub.2 composites as visible light photocatalyst for CO.sub.2 reduction to solar fuels. The in situ carbon doped SnS.sub.2 photocatalyst provide higher efficiency than the undoped pure SnS.sub.2. Also disclosed herein are methods for preparing the catalysts.

Disclosed herein are carbon doped tin disulphide (C—SnS.sub.2) and other SnS.sub.2 composites as visible light photocatalyst for CO.sub.2 reduction to solar fuels. The in situ carbon doped SnS.sub.2 photocatalyst provide higher efficiency than the undoped pure SnS.sub.2. Also disclosed herein are methods for preparing the catalysts.

A hydrocarbon is produced by applying mechanical energy to a metal body containing stainless steel by solid-solid contact so that a contact pressure per unit area is 30 kPa or more, in the presence of a gas containing carbon dioxide and a hydrogen source, thereby adding hydrogen to carbon dioxide. Further, a hydrocarbon is produced by providing a reaction vessel for applying mechanical energy to a metal body by solid-solid contact in the presence of a gas containing carbon dioxide and a hydrogen source, a gas introduction unit for introducing the gas containing carbon dioxide to the reaction vessel, a hydrogen source introduction unit for introducing the hydrogen source to the reaction vessel, and a gas discharge unit for discharging a gas containing the hydrocarbon produced in the reaction vessel, and adding hydrogen to the carbon dioxide in the reaction vessel.

A hydrocarbon is produced by applying mechanical energy to a metal body containing stainless steel by solid-solid contact so that a contact pressure per unit area is 30 kPa or more, in the presence of a gas containing carbon dioxide and a hydrogen source, thereby adding hydrogen to carbon dioxide. Further, a hydrocarbon is produced by providing a reaction vessel for applying mechanical energy to a metal body by solid-solid contact in the presence of a gas containing carbon dioxide and a hydrogen source, a gas introduction unit for introducing the gas containing carbon dioxide to the reaction vessel, a hydrogen source introduction unit for introducing the hydrogen source to the reaction vessel, and a gas discharge unit for discharging a gas containing the hydrocarbon produced in the reaction vessel, and adding hydrogen to the carbon dioxide in the reaction vessel.

A hydrocarbon is produced by applying mechanical energy to a metal body containing stainless steel by solid-solid contact so that a contact pressure per unit area is 30 kPa or more, in the presence of a gas containing carbon dioxide and a hydrogen source, thereby adding hydrogen to carbon dioxide. Further, a hydrocarbon is produced by providing a reaction vessel for applying mechanical energy to a metal body by solid-solid contact in the presence of a gas containing carbon dioxide and a hydrogen source, a gas introduction unit for introducing the gas containing carbon dioxide to the reaction vessel, a hydrogen source introduction unit for introducing the hydrogen source to the reaction vessel, and a gas discharge unit for discharging a gas containing the hydrocarbon produced in the reaction vessel, and adding hydrogen to the carbon dioxide in the reaction vessel.

A hydrocarbon is produced by applying mechanical energy to a metal body containing stainless steel by solid-solid contact so that a contact pressure per unit area is 30 kPa or more, in the presence of a gas containing carbon dioxide and a hydrogen source, thereby adding hydrogen to carbon dioxide. Further, a hydrocarbon is produced by providing a reaction vessel for applying mechanical energy to a metal body by solid-solid contact in the presence of a gas containing carbon dioxide and a hydrogen source, a gas introduction unit for introducing the gas containing carbon dioxide to the reaction vessel, a hydrogen source introduction unit for introducing the hydrogen source to the reaction vessel, and a gas discharge unit for discharging a gas containing the hydrocarbon produced in the reaction vessel, and adding hydrogen to the carbon dioxide in the reaction vessel.

A hydrocarbon is produced by applying mechanical energy to a metal body containing stainless steel by solid-solid contact so that a contact pressure per unit area is 30 kPa or more, in the presence of a gas containing carbon dioxide and a hydrogen source, thereby adding hydrogen to carbon dioxide. Further, a hydrocarbon is produced by providing a reaction vessel for applying mechanical energy to a metal body by solid-solid contact in the presence of a gas containing carbon dioxide and a hydrogen source, a gas introduction unit for introducing the gas containing carbon dioxide to the reaction vessel, a hydrogen source introduction unit for introducing the hydrogen source to the reaction vessel, and a gas discharge unit for discharging a gas containing the hydrocarbon produced in the reaction vessel, and adding hydrogen to the carbon dioxide in the reaction vessel.

A hydrocarbon is produced by applying mechanical energy to a metal body containing stainless steel by solid-solid contact so that a contact pressure per unit area is 30 kPa or more, in the presence of a gas containing carbon dioxide and a hydrogen source, thereby adding hydrogen to carbon dioxide. Further, a hydrocarbon is produced by providing a reaction vessel for applying mechanical energy to a metal body by solid-solid contact in the presence of a gas containing carbon dioxide and a hydrogen source, a gas introduction unit for introducing the gas containing carbon dioxide to the reaction vessel, a hydrogen source introduction unit for introducing the hydrogen source to the reaction vessel, and a gas discharge unit for discharging a gas containing the hydrocarbon produced in the reaction vessel, and adding hydrogen to the carbon dioxide in the reaction vessel.