Porous Catalyst Substrate for Fuel Cell Durability and Activity
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Solution Overview
Problem
Conventional polymer electrolyte fuel cells require high amounts of platinum, leading to high costs, and carbon-supported catalysts suffer from durability issues due to corrosion, especially during start and stop operations, necessitating improvements in catalyst layer durability and mass activity.
Innovation Solution
A catalyst-supporting substrate with a sponge-like structure is developed, featuring a catalyst layer with pores of 5 nm to 400 nm diameter and a long-side to short-side ratio of 1:1 to 10:1, formed by sputtering and heat treatment, which enhances mass activity and durability by promoting proton conductivity and preventing coagulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sputtering method is used to deposit platinum on whisker substrate, then durability is improved, but catalyst utilization efficiency deteriorates due to formation of large platinum blocks
Solution Approach 1:
The patent changes the deposition parameters by using vapor phase deposition at controlled temperatures (200-400°C) rather than standard sputtering conditions. This temperature control prevents excessive platinum aggregation and maintains small particle sizes (5-50 nm), achieving both high durability and high catalyst utilization efficiency
Solution Approach 2:
The patent introduces an ionomer (perfluorosulfonic acid polymer) as an intermediary substance during the vapor phase deposition process. The ionomer acts as a dispersing agent that prevents platinum particles from aggregating into large blocks, maintaining high surface area and catalyst utilization while still providing durable electrode structure
2Quantity of substance
If platinum quantity is reduced to meet cost targets, then cost is improved, but mass activity must be significantly improved to maintain performance
Solution Approach 1:
The patent uses a fluororesin porous substrate with controlled pore size (0.03-10 μm) and high porosity (30-80%). This porous structure provides extremely high surface area for catalyst dispersion, allowing platinum particles to be distributed over a much larger area, thereby increasing the effective mass activity and reducing the total platinum quantity needed while maintaining fuel cell performance
3Productivity
If pore-forming material is melted to create pores in catalyst layer, then catalyst utilization efficiency is improved, but durability deteriorates
Solution Approach 1:
The patent incorporates pores directly into the substrate structure before the catalyst layer is formed. The fluororesin porous substrate is pre-formed with its pore structure, and then the catalyst layer is deposited onto this pre-porous substrate. This preliminary creation of pores eliminates the need for subsequent pore-forming material addition and melting, avoiding durability degradation while maintaining high catalyst utilization efficiency
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 substrate achieves higher mass activity and durability compared to conventional catalysts, with improved catalyst utilization efficiency and proton conductivity, leading to enhanced fuel cell performance and reduced platinum usage.
Implementation Method 1
a platinum catalyst material is deposited on a whisker substrate by sputtering
Implementation Method 2
the pore-forming material in the mixed layer and pore-forming material layer are melted to remove them
Data Source
AI summary
According to one embodiment, a catalyst-supporting substrate comprises a substrate and a catalyst layer including a plurality of pores, the catalyst layer being supported on the substrate. The average diameter of the section of the pore when the catalyst is cut in the thickness direction of the thickness is 5 nm to 400 nm, and the long-side to short-side ratio of the pore on the section is 1:1 to 10:1 in average.