Metal Catalyst with Controlled Metallic Bond State
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Solution Overview
Problem
Conventional metal catalysts with fine metal particles supported on carrier particles face challenges in achieving high catalytic activity due to insufficient exposure of metal elements on the surface, leading to reduced catalytic performance, especially when the particle diameter is 3 nm or less.
Innovation Solution
The catalysts are optimized by adjusting the proportion of metallic bond state to 40% or more, measured by X-ray photoelectron spectrometry, and ensuring a suitable distance between fine metal particles to prevent clustering, while using a reducing agent with weak reducing power and specific carrier materials like carbon black with a BET specific surface area between 500 to 1500 m2/g to maintain high catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of fine metal particles to be supported is increased to enhance catalytic activity, then the catalytic activity is improved, but the distance between adjacent fine metal particles decreases excessively causing plural fine metal particles to behave like one catalyst particle and catalytic activity decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle diameter of fine metal particles to 3 nm or less and adjusting the supported amount to maintain an optimal distance between particles. This quantitative parameter control resolves the contradiction by finding the optimal point where catalytic activity is maximized before particle proximity causes negative effects.
2Reliability
If the particle diameter of fine metal particles is decreased to increase specific surface area, then the catalytic activity is improved, but the proportion of metallic bond state on the surface decreases leading to reduced catalytic performance
Solution Approach 1:
The patent resolves this contradiction by establishing specific parameter ranges: particle diameter of 3 nm or less combined with a metallic bond state proportion of 40% or more. This dual parameter control allows the use of ultra-fine particles for high surface area while maintaining sufficient metallic character for catalytic function through controlled reduction treatment.
Solution Approach 2:
The patent employs reduction treatment (reverse of oxidation) using reducing agents to adjust the metallic bond state proportion. By controlling the reduction process, the patent ensures that fine metal particles maintain adequate metallic character (40% or more) even at ultra-fine sizes, resolving the contradiction between particle size and metallic bond state.
3Length of moving object
If the amount of fine metal particles to be supported is small to maintain adequate distance between particles, then particle distribution is optimized, but sufficient catalytic activity cannot be obtained
Solution Approach 1:
The patent resolves this contradiction by changing the fundamental parameter of particle diameter to 3 nm or less. This ultra-fine sizing allows a higher number of particles to be supported while maintaining adequate inter-particle distance, thus achieving both sufficient catalytic activity (through higher particle count) and optimal distribution (through maintained distance).
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 approach enhances catalytic activity by ensuring a sufficient proportion of exposed metal elements and optimal particle distribution, preventing clustering and maintaining high efficiency even at low temperatures, thus improving the performance of the metal catalysts for fuel cells and automobile exhaust gas applications.
Implementation Method 1
a method comprising the step of reducing ions of metal to be deposited by the action of a reducing agent in a reaction system of a liquid phase containing carrier particles dispersed therein thereby to deposit the metal on the surface of the carrier particles in the form of fine particles
Implementation Method 2
which is ascribed by subjecting to waveform separation of a binding energy peak peculiar to the metal as measured by using an X-ray photoelectron spectrometer
Data Source
AI summary
The present invention relates to a metal catalyst containing fine metal particles, characterized in that the fine metal particles have a particle diameter of 3 nm or less and also have a proportion of metallic bond state of 40% or more, which is ascribed by subjecting to waveform separation of a binding energy peak peculiar to the metal as measured by using an X-ray photoelectron spectrometer. The fine metal particles are preferably fine platinum particles. The fine metal particles are preferably supported on the surface of carrier particles by reducing ions of metal to be deposited through the action of a reducing agent in a reaction system of a liquid phase containing the carrier particles dispersed therein, thereby to deposit the metal on the surface of carrier particles in the form of fine particles. The proportion of metallic bond state of the fine metal particles is adjusted within the above range by reducing after deposition thereby to decrease the oxidation state.