Iridium-Platinum Layered Catalyst for Durable PEMFC Activity
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Solution Overview
Problem
Polymer electrolyte membrane fuel cells (PEMFCs) face challenges in minimizing platinum content while maintaining catalytic activity and durability, as existing electrocatalysts often require expensive precious metals like iridium and gold, which can decrease mass activity and increase costs.
Innovation Solution
A catalyst comprising an iridium layer with a thin platinum layer on top, where the iridium layer has an average thickness of 0.04 to 30 nanometers and the platinum layer has an average thickness of 0.04 to 50 nanometers, with a specific atomic ratio, enhancing the catalyst's surface area and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If iridium is incorporated into the PEMFC ORR electrocatalyst to improve durability, then the catalyst durability is improved, but the mass activity decreases and cost increases
Solution Approach 1:
The patent applies local quality by creating a layered structure where iridium is positioned specifically at the substrate interface rather than being uniformly distributed. The Ir layer (0.04-30 nm) is located at the bottom to provide durability, while the Pt layer (0.04-50 nm) is positioned at the catalytic surface to maintain high mass activity for ORR. This spatial differentiation of material functions resolves the contradiction between durability and mass activity.
2Quantity of substance
If platinum content is minimized to reduce cost, then the catalyst cost is reduced, but the catalytic activity and performance decrease
Solution Approach 1:
The patent uses composite materials by combining iridium and platinum in a layered structure. The Ir/Pt composite leverages the high durability of iridium at the substrate interface and the high catalytic activity of platinum at the surface. This composite approach reduces overall platinum content while maintaining or enhancing both durability and catalytic activity, resolving the contradiction between cost reduction and performance maintenance.
3Reliability
If gold is incorporated to modify catalyst properties, then certain catalytic properties are improved, but mass activity substantially decreases due to surface segregation
Solution Approach 1:
The patent inverts the conventional approach by placing the less catalytically active material (iridium) at the bottom layer rather than mixing it uniformly or placing it at the surface. This inversion ensures that iridium provides structural stability and durability at the interface without compromising the surface catalytic activity, avoiding the surface segregation problem that plagues gold-based catalysts.
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 design improves mass activity, specific surface area, and fuel cell performance by stabilizing the platinum layer and reducing the need for excessive precious metal usage, thereby reducing costs and increasing durability.
Implementation Method 1
The catalyst design improves mass activity, specific surface area, and fuel cell performance by stabilizing the platinum layer
Implementation Method 2
PEMFC electrocatalysts are often in the form of nanometer-scale thin films or particles on support materials
Implementation Method 3
Fuel cells produce electricity via electrochemical oxidation of a fuel and reduction of an oxidant
Implementation Method 4
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
Data Source
AI summary
Catalyst comprising an Ir layer having an outer layer with a layer comprising Pt directly thereon, wherein the Ir layer has an average thickness in a range from 0.04 to 30 nanometers, wherein the layer comprising Pt has an average thickness in a range from 0.04 to 50 nanometers, and wherein the Pt and Ir are present in an atomic ratio in a range from 0.01:1 to 10:1. Catalysts described herein are useful, for example, in fuel cell membrane electrode assemblies.