Metal oxides from acidic solutions
Forming a metal oxide by treating an acidic solution containing a metal to yield a precursor in the form of a semi-liquid, semi-solid or solid, and treating the precursor to yield a product including the metal oxide. An organic or inorganic component may be combined with the precursor to yield a second semi-liquid, semi-solid or solid. The product may be treated to yield a new material. In some cases, the metal oxide has an empirical formula H x M 2 A 1 y -A 2 z , where M represents a transition metal or any combination of transition metals in Groups 3-12; A 1 is a first oxyanion; A 2 is a second oxyanion; 0≤x≤3; 0≤y≤3; 0≤z≤3; and y+z>0.
1. A method comprising:
heating an acidic solution comprising a metal to yield a precursor in the form of a semi-liquid, semi-solid or solid; and
calcining the precursor to yield a product comprising an oxide of the metal,
wherein the acidic solution has a pH of 2 or less, and heating the acidic solution to yield the precursor results in a pH change of 2 or less.
2. The method of claim 1 , wherein the acidic solution comprises a metal-stabilizing agent that stabilizes the metal in the acidic solution.
3. The method of claim 2 , wherein the metal-stabilizing agent decomposes at a temperature less than 100° C.
4. The method of claim 1 , further comprising combining an additive with the acidic solution to modify the acidic solution before heating the acidic solution to yield the precursor, wherein the additive is an organic compound or an inorganic compound, and modifying the acidic solution results in a pH change of 2 or less.
5. The method of claim 4 , wherein the additive comprises an inorganic compound, a carbon-forming agent, or a combination of thereof.
6. The method of claim 1 , wherein calcining the precursor comprises calcining the precursor in air or in a controlled gas environment.
7. The method of claim 1 , wherein the acidic solution comprises at least one oxyanion.
8. The method of claim 7 , wherein the acidic solution comprises two or more compositionally different oxyanions.
9. The method of claim 1 , wherein the product comprises, in its chemical structure, at least two different ligands selected from the group consisting of oxyanions, polyoxoanions, and polyoxyanions.
10. The method of claim 1 , wherein the product comprises, in its chemical structure, protons or structural hydroxyl ions.
11. The method of claim 1 , wherein the metal is a transition metal in Groups 3-12.
12. The method of claim 1 , wherein the acidic solution comprises two or more different metals.
13. The method of claim 1 , wherein the metal is in the form of or derived from a metal salt or complex.
14. The method of claim 1 , further comprising combining an organic or inorganic component with the precursor to yield a second semi-liquid, semi-solid or solid.
15. The method of claim 1 , further comprising treating the product to yield a new material.
16. The method of claim 1 , wherein the metal oxide is a crystalline solid having proton or hydronium ions as charge-balancing cations in the structure.
17. The method of claim 1 , wherein the metal oxide is a proton conductor, an acid catalyst, or a battery material.