Pt-Ni-Ir Catalyst Nanoporous Structure for Fuel Cell
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Solution Overview
Problem
PEMFCs face challenges in minimizing platinum content while maintaining catalytic activity and durability, as the incorporation of iridium for improved oxygen evolution reaction activity can decrease oxygen reduction reaction activity and increase costs.
Innovation Solution
A catalyst comprising nanostructured elements with a catalyst material formula of Pt x Ni y Ir z, where x is between 26.6 and 47.8, y is between 48.7 and 70, and z is between 1 and 11.4, with layers of platinum, nickel, and iridium, and nanoporous structures formed by dealloying, which improves mass activity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If platinum content is minimized to reduce cost, then catalyst cost is reduced, but catalytic activity and PEMFC device performance decrease
Solution Approach 1:
The patent applies parameter changes by optimizing the platinum content to a specific range (26.6-47.8 at%) rather than using conventional high Pt content catalysts. This parameter optimization, combined with the alloying effect of Ni and Ir, maintains catalytic activity while significantly reducing Pt loading and cost
2Area of stationary object
If nanoporous structure is formed by dealloying to increase specific area, then specific area increases and cost is reduced, but catalyst durability may be affected
Solution Approach 1:
The patent applies preliminary action by incorporating Ir into the catalyst structure before the dealloying process. This pre-incorporation ensures that Ir is present to stabilize the nanoporous structure formed during dealloying, preventing excessive coarsening and maintaining both high specific area and long-term durability
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 catalyst retains mass activity and specific area performance after accelerated aging, enhancing durability whether iridium is incorporated in the bulk or surface, before or after annealing, and nanoporosity formation.
Implementation Method 1
PEMFCs typically require the use of electrocatalysts to improve the reaction rate of the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR)
Implementation Method 2
One method of forming nanoporous PEMFC electrocatalysts is via dealloying of a transition metal rich Pt alloy precursor, such as a PtNi alloy with 30 at.% Pt and 70 at.% Ni. During dealloying, the precursor is exposed to conditions where the transition metal is dissolved and the surface Pt has sufficient mobility to allow exposure of subsurface transition metal and formation of nanoscale ligaments which separate the nanopores.
Implementation Method 3
incorporation of certain transition metals into the Pt lattice is believed to induce contraction of the Pt atoms at the catalyst surface, which increases the kinetic reaction rate by modification of the molecular oxygen binding and dissociation energies
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~3E
AI summary
Catalyst (100) comprising nanostructured elements (102) comprising microstructured whiskers (104) having an outer surface (105) at least partially covered by a catalyst material (106) having the formula PtxNiyIrz, wherein x is in a range from 26.6 to 47.8, y is in a range from 48.7 to 70, and z is in a range from 1 to 11.4. Catalysts described herein are useful, for example, in fuel cell membrane electrode assemblies.