Noble Metal Alloy Catalysts via Polyol Reduction
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Solution Overview
Problem
Existing methods for manufacturing noble metal alloy catalysts, such as PtRu and PtCo, often result in incomplete alloy formation and particle agglomeration due to heat treatment and calcination processes, leading to low degrees of alloying and larger crystallite sizes.
Innovation Solution
A two-step sequential reduction process in polyol solvents, where the first metal is activated at 80-160°C and then the noble metal is added, followed by further heating to 160-300°C, ensuring uniform reduction and deposition on a support material without the need for heat treatment, thereby achieving high alloying and small crystallite sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heat treatment and calcination processes are used to manufacture noble metal alloy catalysts, then the catalysts can be formed, but the degree of alloying becomes low and crystallite size increases due to particle agglomeration
Solution Approach 1:
The patent changes the chemical parameters of the reduction process by using polyol solvents with specific functional groups that can reduce metal ions at lower temperatures. This allows the formation of highly alloyed catalysts with small crystallite sizes without requiring high-temperature heat treatment that would cause particle agglomeration and reduce alloying degree.
Solution Approach 2:
The patent introduces polyol solvents as intermediary reducing agents that mediate the formation of noble metal alloys. These polyols enable controlled reduction at lower temperatures, preventing direct high-temperature processing that leads to particle growth, while still achieving complete alloy formation through their unique chemical reducing capability.
2Length of moving object
If conventional reduction methods are used, then the manufacturing process is simple, but particle agglomeration occurs leading to larger crystallite sizes
Solution Approach 1:
The patent changes the temperature parameter by conducting the reduction process at lower temperatures using polyol solvents. This temperature control prevents particle agglomeration and maintains small crystallite sizes while the polyol solvent provides steric stabilization to maintain particle stability throughout the process.
Solution Approach 2:
The polyol solvent acts as an intermediary that simultaneously provides reduction capability and steric stabilization. The long hydrocarbon chains of the polyols adsorb on particle surfaces, preventing agglomeration and maintaining small crystallite sizes, while the hydroxyl groups provide reducing capability for metal ion reduction.
3Manufacturing precision
If high temperature processing is applied, then reduction is more complete, but sintering and particle growth occur reducing catalyst performance
Solution Approach 1:
The patent fundamentally changes the temperature parameter from high-temperature processing to low-temperature processing by utilizing the unique reducing capability of polyol solvents. This allows complete alloy formation to occur at lower temperatures where sintering and particle growth are suppressed, maintaining small crystallite sizes and high catalyst performance.
Solution Approach 2:
The patent replaces the thermal energy-driven reduction mechanism with a chemically-driven reduction mechanism using polyol solvents. Instead of relying on high temperature to drive reduction, the patent uses the chemical reducing capability of polyols, substituting thermal processing with chemical processing that occurs at lower temperatures.
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
This method achieves a high degree of alloying and small crystallite sizes, enhancing catalyst performance by improving tolerance to carbon monoxide poisoning and increasing activity in fuel cells and CO oxidation processes, while avoiding sintering and particle growth.
Implementation Method 1
A mixture of metal compounds in a polyol solvent is converted to a colloidal particle suspension by raising the pH and heating the solution
Implementation Method 2
The mixture is subsequently heated to 80 to 160° C. In the next step, the precursor compound of a second metal is added to the slurry. After a certain period of time, the temperature is further increased in a range of 160 to 300° C.
Implementation Method 3
A mixture of metal compounds in a polyol solvent is converted to a colloidal particle suspension
Data Source
AI summary
The present invention provides a method for manufacture of supported noble metal based alloy catalysts with a high degree of alloying and a small crystallite size. The method is based on the use of polyol solvents as reaction medium and comprises of a two-step reduction process in the presence of a support material. In the first step, the first metal (M1=transition metal; e.g. Co, Cr, Ru) is activated by increasing the reaction temperature to 80 to 160° C. In the second step, the second metal (M2=noble metal; e.g. Pt, Pd, Au and mixtures thereof) is added and the slurry is heated to the boiling point of the polyol solvent in a range of 160 to 300° C. Due to this two-step method, an uniform reduction occurs, resulting in noble metal based catalysts with a high degree of alloying and a small crystallite size of less than 3 nm. Due to the high degree of alloying, the lattice constants are lowered. The catalysts manufactured according to the method are used as electrocatalysts for polymer electrolyte membrane fuel cells (PEMFC), direct-methanol fuel cells (DMFC) or as gas phase catalysts for CO oxidation or exhaust gas purification.