KR-20260065771-A - SUB-NANOCLUSTER CATALYSTS WITH CARBON SHELL, ULTRA-LOW PLATINUM LOADINGS AND ITS ALLOY FOR OXYGEN REDUCTION REACTION

Abstract

The present invention relates to a subnanocluster catalyst having subnano-level platinum or a platinum alloy as catalytic active particles, wherein a carbon shell is formed on the surface of the catalytic active particles, and can provide a catalyst with excellent durability and activity while drastically reducing the amount of platinum used.

Inventors

• 함형철
• 이어윤
• 이현주
• 신상용

Assignees

• 인하대학교 산학협력단
• 한국과학기술원

Dates

Publication Date

20260511

Application Date

20260421

Claims (5)

1. carbon shell; and A catalyst for a fuel cell comprising platinum or a platinum alloy located inside a carbon shell, The above platinum or platinum alloy is a sub-nanocluster, and An overlap is formed between the sp2 orbitals of the carbon shell and the d orbitals of the subnanocluter platinum or platinum alloy, and The carbon shell mentioned above is graphene, and The above sub-nanoclust platinum or platinum alloy has a diameter greater than or equal to the diameter of a platinum atom and less than 1.0 nm, and The above catalyst forms the carbon shell by supporting a platinum precursor on a polystyrene-based carbon carrier synthesized without using a vinylbenzyl azide crosslinking agent and then heat-treating it. The above catalyst is a fuel cell catalyst that maintains an activity per mass of platinum of at least 85% of the initial value even after 10,000 cycles under a durability evaluation in which a cyclic voltammetry curve is repeatedly measured in a voltage range of 0.6V to 1.0V (vs. RHE) in a 0.1M HClO₄ electrolyte.
2. In paragraph 1, The catalyst active site in the above fuel cell catalyst is a cross-section or surface of a carbon shell.
3. In paragraph 2, The catalytic active reaction occurring at the above-mentioned catalytic active site is an oxygen reduction reaction, which is a catalyst for fuel cells.
4. In paragraph 1, The above sub-nanoclust platinum or platinum alloy is a catalyst for a fuel cell represented by the following chemical formula 1. [Chemical Formula 1] Pt x M y (Pt is platinum, M is one selected from the group consisting of 3d, 4d, and 5d transition metals, and x > 0, y ≥ 0, x+y ≤ 60.)
5. In paragraph 1, The above-mentioned subnanocluster platinum or platinum alloy is a catalyst for a fuel cell having one or more shapes selected from the group consisting of spherical, icosahedron, octahedron, cuboctahedron, and cubic.

Description

Sub-nanocluster catalysts for oxygen reduction reaction comprising ultra-low platinum, its alloys, and a carbon shell The present invention relates to a novel subnanocluster catalyst for oxygen reduction reactions comprising a carbon shell and subnanocluster platinum or a platinum alloy, which can be utilized as an air electrode catalyst for a Polymer Electrolyte Membrane Fuel Cell (PEMFC) and can drastically reduce the amount of platinum used in catalyst manufacturing. Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are fuel cells comprising a polymer electrolyte capable of hydrogen ion exchange, a fuel electrode where hydrogen oxidation occurs, and an air electrode where oxygen reduction occurs as their main components. They are attracting attention as next-generation fuel cells due to their advantages of being environmentally friendly and capable of operating at low temperatures, as they produce water as a byproduct. Each electrode of a polymer electrolyte fuel cell consists of a catalyst for the reaction and a support for the catalyst. Most polymer electrolyte fuel cells currently developed use platinum-supported carbon catalysts as electrode catalysts, in which platinum (Pt) particles of size 2 to 5 nm are dispersed on a carbon (C) support. Among the two electrodes, which are divided into a fuel electrode and an air electrode, hydrogen oxidation occurs at the fuel electrode and oxygen reduction reaction (ORR) occurs at the air electrode. Since the oxygen reduction reaction at the air electrode is kinetically about five times slower than the hydrogen oxidation reaction at the fuel electrode, the oxygen reduction reaction at the air electrode catalyst effectively determines the overall performance of the cell, and a simple way to improve the oxygen reduction reaction is to increase the amount of platinum catalyst used. However, since platinum itself is a very expensive precious metal and the cost of catalyst materials containing platinum accounts for 45% of the total cost of polymer electrolyte fuel cells using platinum (Pt)-based catalysts, there is a need to develop technology that can drastically reduce the amount of platinum used. Accordingly, as an alternative to reduce the amount of Pt while increasing activity and durability, research is being conducted on the development of catalysts using platinum (Pt)-based nickel (Ni) or cobalt (Co) alloys, such as U.S. Patent No. 9960430. However, there are difficulties in commercialization of such platinum-transition metal alloys because internal metals emerge to the surface and leach into the electrolyte during the operating environment of the battery, resulting in reduced durability. Therefore, for the commercialization of polymer electrolyte fuel cells, it is urgent to develop catalyst materials with new compositions and structures based on ultra-low platinum that can reduce the amount of platinum catalyst used in the air electrode to be economical, while simultaneously maintaining the activity and durability of the oxygen reduction reaction above a certain level. FIG. 1 is a flowchart illustrating the process of fabricating a catalyst for oxygen reduction reaction containing sub-nanocluster catalyst active particles according to the present invention. FIG. 2 shows the structure of a pure platinum cluster (Pt 6 ) and a platinum-based alloy cluster (Pt 3 Fe 3 ) included in a catalyst for an oxygen reduction reaction according to one embodiment of the present invention. FIG. 3 shows the structure of a catalyst ((A)) comprising sub-nanocluter platinum (Pt 6 ) and a catalyst ((B)) comprising a sub-nanocluter platinum alloy (Pt 3 Fe 3 ) as catalysts according to one embodiment of the present invention, showing sub-nanocluter particles supported on a graphite support and a carbon shell surrounding them. FIG. 4 shows the possible 2-electron and 4-electron oxygen reduction reaction mechanisms in the carbon shell cross-section of a catalyst according to one embodiment of the present invention. FIG. 5 shows a structure in which oxygen is adsorbed on a carbon shell cross-section in a catalyst comprising subnanocluster platinum (Pt 6 ) according to one embodiment of the present invention. FIG. 6 shows the onset potential and free energy according to the reaction mechanism of the oxygen reduction reaction in a catalyst comprising subnanoclustered platinum (Pt 6 ) according to one embodiment of the present invention (U onset potential, Uocv open potential). FIG. 7 shows the hydrogen peroxide (hydrogen peroxide) desorption energy and hydrogen peroxide decomposition activation energy in a catalyst comprising subnanocluster platinum (Pt 6 ) according to one embodiment of the present invention. FIG . 8 shows a structure in which oxygen is adsorbed on a carbon shell cross-section in a catalyst comprising a subnanocluster platinum alloy ( Pt₃Fe₃ ) according to one embodiment of the present invention. FIG. 9 shows the onset potential and free energy according to the reaction