Hollow Multilayered Core/Shell Catalyst Particles for Fuel Cells
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Solution Overview
Problem
Current electrocatalysts for fuel cells, particularly those based on platinum alloys, lack sufficient activity and durability to meet commercial requirements for widespread adoption, due to issues with precious metal agglomeration and core dissolution in acidic environments.
Innovation Solution
Development of hollow multilayered base metal-precious metal core/shell catalyst particles with a concentration gradient in the intermediate layer, featuring a precious metal inner and outer shell, and a base metal-precious metal alloy intermediate layer, which are synthesized using a method involving the formation of a base metal core, co-deposition of a precious metal alloy shell, and subsequent acid leaching to create a hollow structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid core/shell structure with precious metal shell is used, then catalytic activity is improved, but precious metal content increases and cost increases
Solution Approach 1:
The solid core is segmented into a hollow structure by removing the base metal core through acid leaching, while preserving the precious metal shell. This creates a hollow sphere with thin shell walls that maintains catalytic activity while reducing precious metal content by approximately 50% compared to solid core/shell particles of the same outer diameter.
Solution Approach 2:
The precious metal is concentrated locally at the shell surface where catalytic reactions occur, rather than being distributed throughout a solid core. The shell thickness is optimized to provide sufficient catalytic material at the reactive interface while minimizing total precious metal usage. The hollow interior space is utilized for additional functional purposes.
2Quantity of substance
If base metal core is used to reduce cost, then precious metal content is reduced, but core dissolution in acidic environment occurs
Solution Approach 1:
The base metal core is completely extracted through acid leaching, removing the unstable component that would dissolve in acidic fuel cell environments. Only the precious metal shell remains, which is chemically stable and resistant to acid corrosion, thereby eliminating the durability problem while maintaining low precious metal content.
Solution Approach 2:
The acid leaching process, which could be harmful if it dissolved the precious metal, is instead used beneficially to remove only the base metal core while leaving the precious metal shell intact. The acid selectively attacks the base metal due to differences in chemical reactivity, converting a potential harm into a useful separation process.
3Quantity of substance
If hollow structure is created by removing base metal core, then precious metal content is reduced and surface area is increased, but manufacturing complexity increases
Solution Approach 1:
The base metal core is formed first as a sacrificial template before the precious metal shell is deposited. This preliminary formation of the core structure simplifies the overall process, as the core provides a ready-made template for shell deposition. The core is then removed in a single acid leaching step, avoiding the need for complex hollow structure fabrication techniques.
Solution Approach 2:
The base metal core acts as an intermediary object that facilitates the formation of the hollow structure. It serves as a temporary template during manufacturing, enabling simple shell deposition, and is then removed to create the final hollow product. This intermediary approach is simpler than attempting to directly fabricate hollow structures with precise shell thickness control.
4Reliability
If precious metal shell thickness is increased, then catalytic activity is improved, but precious metal content increases
Solution Approach 1:
The shell thickness is optimized as a critical parameter to balance catalytic activity and precious metal content. By controlling the deposition conditions and precursor ratios, the shell thickness is precisely controlled to provide sufficient catalytic material at the surface while minimizing total precious metal usage. The hollow structure amplifies the effective surface area, allowing thinner shells to achieve the same catalytic performance.
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 resulting catalysts exhibit enhanced specific activity and reduced precious metal content, with improved stability and catalytic performance in fuel cell applications, offering a higher exposed surface area and increased durability against acidic leaching.
Implementation Method 1
The formation of base metal cores is often performed by reducing a base metal salt in a polyol
Implementation Method 2
removing the base metal core in the last step
Data Source
AI summary
The present invention is directed to hollow catalyst particles comprising a layered shell structure and to a method of their manufacture. The catalyst particles have the general formula Hcore/PMinner shell/IL/PMouter shell in which Hcore is the hollow core, PMinner shell is a precious metal forming the innermost layer of the shell, IL is an intermediate layer comprising a base metal/precious metal alloy, and PMouter shell is a precious metal forming the outermost layer of the shell. The precious metal is selected from Pt, Ir and Pd and mixtures or alloys thereof, and IL is an intermediate layer comprising a base metal/precious metal alloy wherein the concentration of the base metal changes from the periphery of the hollow core to the outer surface of the intermediate layer. The base metal is selected from Co, Ni, and Cu and mixtures thereof.