Autogenic reaction synthesis of photocatalysts for solar fuel generation
In one preferred embodiment, a photocatalyst for conversion of carbon dioxide and water to a hydrocarbon and oxygen comprises at least one nanoparticulate metal or metal oxide material that is substantially free of a carbon coating, prepared by heating a metal-containing precursor compound in a sealed reactor under a pressure autogenically generated by dissociation of the precursor material in the sealed reactor at a temperature of at least about 600° C. to form a nanoparticulate carbon-coated metal or metal oxide material, and subsequently substantially removing the carbon coating. The precursor material comprises a solid, solvent-free salt comprising a metal ion and at least one thermally decomposable carbon- and oxygen-containing counter-ion, and the metal of the salt is selected from the group consisting of Mn, Ti, Sn, V, Fe, Zn, Zr, Mo, Nb, W, Eu, La, Ce, In, and Si.
1. A photocatalyst for conversion of carbon dioxide and water into a hydrocarbon and oxygen, the photocatalyst comprising at least one metal oxide material that is substantially free of a carbon coating, prepared by heating a metal-containing precursor compound in a sealed reactor under a pressure autogenically generated by dissociation of the precursor material in the sealed reactor at a temperature of at least about 400° C. to form a nanoparticulate carbon-coated metal or metal oxide material, and subsequently substantially removing the carbon coating; wherein:
the precursor material comprises a solid, solvent-free salt comprising a metal on and at least one thermally decomposable carbon- and oxygen-containing counter-ion;
the metal oxide consists of a mixture of SnO 2 nanoparticles and TiO 2 nanoparticles; the SnO 2 consists essentially of rutile SnO 2 that is substantially free of a carbon coating, and is formed by thermal reaction of tin ethoxide in a sealed reactor at a temperature of about 600° C. under an autogenically generated pressure of up to about 100 pounds-per square-inch (psi) to form a nanoparticulate carbon-coated rutile SnO 2 powder, and subsequently substantially removing the carbon coating;
the TiO 2 consists essentially of carbon-doped anatase TiO 2 that is substantially free of a carbon coating, and is formed by thermal reaction of titanium acetoacetonate in a sealed reactor at a temperature of about 700° C. under an autogenically generated pressure of up to about 150 pounds-per square-inch (psi) to form a nanoparticulate carbon-coated anatase TiO 2 powder, and subsequently substantially removing the carbon coating;
the SnO 2 nanoparticles have a particle size in the range of about 10 to about 20 nm; and the TiO 2 nanoparticles have a particle size in the range of about 10 to about 30 nm.
2. A photocatalyst for conversion of carbon dioxide and water into a hydrocarbon and oxygen, the photocatalyst comprising nanoparticles of carbon-doped anatase TiO 2 that are substantially free of a carbon coating, and nanoparticles of rutile SnO 2 that are substantially free of a carbon coating.
3. The photocatalyst of claim 2 , wherein the nanoparticles of SnO 2 have a particle size in the range of about 10 to about 20 nm, and the nanoparticles of TiO 2 have a particle size in the range of about 10 to about 30 nm.