Method of manufacturing metal single-atom catalysts
A method is disclosed for preparing a metal single-atom catalyst for a fuel cell including the steps of depositing metal single atoms to a nitrogen precursor powder, mixing the metal single atom-deposited nitrogen precursor powder with a carbonaceous support, and carrying out heat treatment. The step of depositing metal single atoms is carried out by sputtering, thermal evaporation, E-beam evaporation or atomic layer deposition. The method uses a relatively lower amount of chemical substances as compared to conventional methods, is eco-friendly, and can produce a single-atom catalyst at low cost. In addition, unlike conventional methods which are limited to certain metallic materials, the present method can be applied regardless of the type of metal.
1. A method for preparing a metal single-atom catalyst, comprising the steps of:
(1) depositing metal single atoms on a nitrogen precursor powder by sputtering using argon as a sputtering gas under a working pressure of 0.1-5 mTorr and an electric power intensity of 1-20 W for 1-5 hours;
(2) mixing the metal single atom-deposited nitrogen precursor powder formed in step (1) with a carbonaceous support to form a mixed powder;
(3) carrying out heat treatment; and
wherein the mixing of the metal single atom-deposited nitrogen precursor powder with a carbonaceous support at step (2) does not use liquid.
2. A method as in claim 1 wherein the working pressure is 0.1 to 2 mTorr.
3. A method as in claim 1 wherein the metal single atom is at least one selected from the group consisting of platinum, gold, palladium, cobalt, silver, rhodium, iridium, ruthenium, nickel, iron, copper, manganese, vanadium, chromium, molybdenum, yttrium, lanthanum, cerium, zirconium, titanium, tantalum and osmium.
4. A method as in claim 1 wherein the nitrogen precursor powder is at least one selected from the group consisting of melamine, glucosamine, urea, thiourea, dicyandiamide and 2-cyanoquanidine.
5. A method as in claim 1 wherein the carbonaceous support is at least one selected from the group consisting of carbon nanotubes, carbon nanofibers, graphene, reduced graphene oxide (rGNO), carbon black, graphite, reduced graphite oxide (rGO) and carbon spheres.
6. A method as in claim 1 wherein the mixing at step (2) is carried out at a weight ratio of the metal single atom-deposited nitrogen precursor powder to the carbonaceous support of 100-500:1.
7. A method as in claim 1 wherein the heat treatment in step (3) is carried out under vacuum, or under at least one gaseous atmosphere selected from the group consisting of argon, nitrogen, ammonia, hydrogen, and helium, at 400-1000° C. for 0.5-4 hours.
8. A method as in claim 1 wherein the metal single-atom catalyst is at least one selected from a catalyst for oxygen reduction, catalyst for hydrogen generation, catalyst for carbon dioxide reduction, catalyst for oxygen generation, catalyst for hydrogen oxidation, catalyst for ammonia reduction and a catalyst for a fuel cell electrode.
9. A method for preparing a metal single-atom catalyst according to claim 1 , which further comprises a step of vacuum drying the nitrogen precursor powder before step (1); and
wherein the nitrogen precursor powder is melamine;
the metal single atoms are platinum;
the deposition is carried out through sputtering;
the sputtering is carried out at a working pressure of 0.1-2 mTorr;
the carbonaceous support is reduced graphite oxide (rGO);
the mixing is carried out at a weight ratio of the metal single atom-deposited nitrogen precursor powder to the carbonaceous support of 200-300:1;
the heat treatment is carried out under an argon gas atmosphere at 700-900° C. for 1-3 hours;
the metal single atoms in the metal single-atom catalyst have an average size of 0.1-0.3 nm; and
wherein platinum, nitrogen, and carbon are distributed homogenously in the catalyst, and wherein X-ray diffraction of the catalyst reveals no crystalline structure related to platinum.