De-alloyed PtXY Catalyst Surface Composition for Fuel Cell Cathodes
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Solution Overview
Problem
Current catalysts for the oxygen reduction reaction in fuel cells, particularly those based on platinum alloys, face challenges in achieving optimal activity and stability, leading to inefficiencies in platinum usage and increased costs due to high catalyst loading.
Innovation Solution
A de-alloyed catalyst of formula PtXY, where X is Ni, Co, or Cr, and Y is Zn, Al, Sn, Be, Pb, Ga, V, In, Y, Sr, or Ti, with a surface atomic composition significantly lower than the bulk, achieved through a leaching process, enhancing the oxygen reduction reaction activity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum alloy catalysts are used for oxygen reduction reaction, then catalytic activity is improved, but platinum loading and cost increase
Solution Approach 1:
The patent changes the surface composition parameters of the catalyst by creating a core-shell structure where the surface is enriched with platinum through selective leaching. This parameter change at the surface level (higher Pt concentration) provides high catalytic activity while the bulk composition can be optimized to reduce overall platinum loading, thus resolving the contradiction between activity and quantity.
Solution Approach 2:
The patent employs a composite catalyst structure combining platinum with base metals (Ni, Co, Cr) in a core-shell configuration. The composite material leverages the high catalytic activity of platinum at the surface while using cheaper base metals in the core, thereby reducing overall platinum content while maintaining or enhancing catalytic performance for oxygen reduction reaction.
2Reliability
If platinum alloy catalysts are used for oxygen reduction reaction, then catalytic activity is improved, but catalyst cost increases
Solution Approach 1:
By modifying the surface composition to be platinum-enriched through controlled leaching processes, the patent achieves high catalytic activity with reduced overall platinum content. This parameter optimization at the surface level allows for lower total platinum loading, directly reducing catalyst manufacturing cost while preserving the required catalytic activity.
Solution Approach 2:
The composite catalyst structure combines expensive platinum with cheaper base metals (Ni, Co, Cr) in a core-shell architecture. This material composition strategy reduces the quantity of expensive platinum required, thereby lowering catalyst cost while the platinum-rich surface maintains high catalytic activity for the oxygen reduction reaction.
3Quantity of substance
If de-alloyed catalyst with surface composition control is used, then platinum usage is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies selective leaching to extract (remove) base metals (Ni, Co, Cr) from the alloy surface, leaving behind a platinum-enriched surface layer. This extraction process creates the desired core-shell structure with reduced overall platinum content while achieving high surface platinum concentration, thus reducing total platinum usage despite the added manufacturing step.
Solution Approach 2:
The catalyst is first synthesized as a homogeneous alloy precursor with controlled composition before undergoing selective leaching. This preliminary alloy formation step establishes the foundation for subsequent surface enrichment, allowing precise control over final surface composition and enabling reduced platinum usage through the pre-designed core-shell architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The de-alloyed catalyst demonstrates improved activity and stability, reducing platinum usage and costs while maintaining high performance in fuel cells, specifically at the cathode of proton exchange membrane fuel cells.
Implementation Method 1
subjecting the catalyst alloy precursor to conditions sufficient to leach a portion of X and/or Y from the catalyst alloy precursor to provide the de-alloyed catalyst
Implementation Method 2
an electrochemical reduction of oxygen at the cathode... The chemical energy of the fuel and the oxidant is converted to electrical energy and heat
Data Source
AI summary
A de-alloyed catalyst of formula PtXY, wherein X is selected from the group consisting of Ni, Co and Cr; and Y is selected from the group consisting of Zn, Al, Sn, Be, Pb, Ga, V, In, Y, Sr and Ti; characterised in that the total atomic composition relative to Pt of X and Y at the surface of the de-alloyed catalyst as determined from X-ray photoelectron spectroscopy is between 20 and 99% lower than the total atomic composition relative to Pt of X and Y in the bulk of the de-alloyed catalyst is disclosed.