Highly active, robust and versatile multifunctional, fully non-noble metals based electro-catalyst compositions and methods of making for energy conversion and storage
The invention provides noble metal-free electro-catalyst compositions for use in acidic media, e.g., acidic electrolyte. The noble metal-free electro-catalyst compositions include non-noble metal absent of noble metal. The non-noble metal is non-noble metal oxide, and typically in the form of any configuration of a solid or hollow nano-material, e.g., nano-particles, a nanocrystalline thin film, nanorods, nanoshells, nanoflakes, nanotubes, nanoplates, nanospheres and nanowhiskers or combinations of myriad nanoscale architecture embodiments. Optionally, the noble metal-free electro-catalyst compositions include dopant, such as, but not limited to halogen. Acidic media includes oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, and direct methanol fuel cells and oxygen evolution reaction (OER) in PEM-based water electrolysis and metal air batteries, and hydrogen generation from solar energy and electricity-driven water splitting.
1. A method for preparing a noble metal-free electro-catalyst for an acidic electrolyte in a proton exchange membrane-based system, comprising:
combining a non-noble metal oxide precursor with a precipitation or reaction agent to form a non-noble metal oxide nano-material;
separating the nano-material;
drying the nano-material; and
forming a noble metal-free oxide nano-material of the general formula 1:
(a x b y )O z (I)
wherein the a is titanium, vanadium, iron, chromium, tantalum, tin, niobium, tungsten, molybdenum, yttrium, scandium, copper, zinc, cobalt, nickel, lanthanum, cerium, neodymium, erbium, gadolinium, ytterbium and mixtures thereof, b is Mn, O is oxygen, x and y are each a number greater than 0 and less than or equal to 2, x and y being the same or different, and z is a number that is greater than 0 and less than or equal to 4,
wherein the noble metal-free oxide nano-material is in a form selected from the group consisting of nano-particle, nanocrystalline thin film, nanorod, nanoshell, nanoflake, nanotube, nanoplate, nanosphere, nanowhisker, and combinations thereof, and
wherein the proton exchange membrane-based system is an oxygen evolution reaction in an acidic electrolyte proton exchange membrane-based water electrolyzer, or an oxygen reduction reaction in an acidic electrolyte proton exchange membrane-based fuel cell.
2. The method of claim 1 , further comprising introducing a dopant precursor prior to the step of drying the nano-material.
3. The method of claim 1 , wherein the non-noble metal oxide precursor is manganese acetate tetrahydrate.
4. The method of claim 3 , wherein the precipitation or reaction agent is potassium permanganate.
5. The method of claim 1 , wherein the non-noble metal oxide nano-material comprises manganese dioxide nanoparticles.
6. The method of claim 2 , wherein the dopant precursor is ammonium fluoride.
7. The method of claim 6 , wherein the noble metal-free oxide nano-material is fluorine-doped manganese oxide nano-material.
8. The method of claim 1 , further comprising applying the noble metal-free electro-catalyst to a substrate to form an electrode.
9. The method of claim 1 , wherein the noble metal-free oxide nano-material comprises a dopant according to the general formula II:
(a x b y )O z :w c
wherein a, b, x, y, and z are as defined in claim 7 , and
wherein c is the dopant and w is from greater than 0% by weight to about 20% by weight, based on total weight of the noble metal-free electro-catalyst.
10. The method of claim 9 , wherein the dopant is selected from the group consisting of at least one element from Groups III, V, VI and VII of the Periodic Table, wherein Group III is in reference to the Periodic Table Group including at least aluminum and boron therein, Group V is in reference to the Periodic Table Group including at least nitrogen, phosphorous, arsenic, antimony, and bismuth therein, Group VI is in reference to the Periodic Table Group including at least sulfur, selenium, and tellurium therein, and Group VII is in reference to the Period Table Group including at least fluorine, chlorine, bromine, and iodine therein.
11. The method of claim 10 , wherein the dopant is selected from the group consisting of fluorine, chlorine, bromine, iodine, sulfur, selenium, tellurium, nitrogen, phosphorous, arsenic, antimony, bismuth, aluminum, boron and mixtures thereof.
12. The method of claim 9 , wherein the dopant is present in an amount from about 10 to about 15 weight percent based on total weight of the noble metal-free electro-catalyst.
13. The method of claim 9 , wherein the non-noble metal oxide nano-material is a binary metal oxide comprising copper oxide and manganese oxide, and the dopant is fluorine.
14. The method of claim 9 , wherein x is 1.5, y is 1.5, z is 4 and w is 5, 10, or 15 percent by weight.
15. The method of claim 9 , wherein x is 1.5, y is 1.5, z is 2.75 and w is 1.25 percent by weight.