Ce-Pr-Zr Composite Oxide for Wide-Temperature Oxygen Storage
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Solution Overview
Problem
Current composite oxides used as co-catalysts for exhaust gas purification and oxygen reduction in fuel cells have insufficient oxygen absorbing and desorbing capabilities, particularly at lower temperatures, which affects the efficiency of exhaust gas purification and the high cost of platinum catalysts in fuel cells.
Innovation Solution
A composite oxide comprising Ce, Pr, and Zr, with specific atomic percentages and optionally other elements, that lacks a tetragonal crystal phase from zirconium oxide, exhibiting large oxygen absorption and desorption capabilities over a wide temperature range without a large specific surface area, suitable for use as a co-catalyst in exhaust gas purification and oxygen reduction in fuel cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional composite oxides containing Ce and Zr are used as co-catalysts, then the catalyst structure is simple and easy to manufacture, but the oxygen absorbing and desorbing capability is insufficient particularly at lower temperatures
Solution Approach 1:
The patent uses a composite oxide material comprising Ce, Pr, and Zr in specific atomic percentage ranges (Ce: 10-80 at%, Pr: 10-60 at%, Zr: 10-60 at%). This composite material approach combines the oxygen storage capacity of cerium with the low-temperature oxygen absorption capability of praseodymium and the structural stability of zirconium, achieving superior oxygen absorbing and desorbing capability across a wide temperature range while maintaining catalyst structural integrity
Solution Approach 2:
The patent optimizes specific parameter ranges including atomic percentages of each element (Ce: 10-80 at%, Pr: 10-60 at%, Zr: 10-60 at%), temperature ranges for oxygen absorption (enhanced at lower temperatures compared to conventional catalysts) and desorption (400-700°C), and crystal phase composition (containing cubic, hexagonal, and/or fluorite phases but excluding tetragonal zirconia phase). These parameter optimizations enable the catalyst to maintain high oxygen absorbing and desorbing capability under varying operating conditions
2Reliability
If the specific surface area is increased to improve oxygen absorption, then the oxygen absorbing capability improves, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating praseodymium alongside cerium and zirconium in optimized atomic ratios. This compositional parameter change enables the material to achieve enhanced oxygen absorption capability through the electronic structure and oxygen mobility properties of praseodymium, without requiring increases in specific surface area or complex manufacturing processes
Solution Approach 2:
While not explicitly focusing on increasing surface area, the patent utilizes the inherent porous structure of the composite oxide material with cubic, hexagonal, and/or fluorite crystal phases. The porous nature of these crystal structures provides sufficient oxygen absorption capacity through bulk material properties rather than surface area dependence, simplifying manufacturing requirements
3Productivity
If platinum is used as the main catalyst for exhaust gas purification and oxygen reduction, then the catalytic activity is high, but the cost becomes prohibitively high
Solution Approach 1:
The patent replaces expensive platinum with a cost-effective composite oxide material comprising Ce, Pr, and Zr. This non-precious metal composite oxide provides sufficient catalytic activity for oxygen reduction reactions in fuel cells and exhaust gas purification, eliminating the need for costly platinum while maintaining productivity. The composite oxide acts as a co-catalyst that enhances the performance of base metal catalysts or functions as a standalone catalytic material
Solution Approach 2:
The patent employs a composite oxide material with specific composition ratios (Ce: 10-80 at%, Pr: 10-60 at%, Zr: 10-60 at%) to achieve catalytic functionality that replaces platinum. The synergistic combination of cerium (oxygen storage), praseodymium (low-temperature oxygen absorption), and zirconium (structural stability) creates a material with high catalytic activity for oxygen reduction and exhaust gas purification reactions, providing a cost-effective alternative to precious metal 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 composite oxide achieves significant oxygen absorption and desorption across a wide temperature range, enhancing exhaust gas purification efficiency and reducing the need for platinum in fuel cells by improving oxygen reduction reactions.
Implementation Method 1
A composite oxide... having large oxygen absorption and desorption capabilities over a wide temperature range
Implementation Method 2
a co-catalyst absorbs oxygen due to change of valency of Ce contained therein from three to four under an oxidizing atmosphere, and desorbs oxygen due to change of the cerium valency from four to three under a reducing atmosphere
Implementation Method 3
The oxygen reduction reaction at the cathode, 1/2O 2 + 2H +
Data Source
Figure 1~3
AI summary
A composite oxide is provided which has large oxygen absorption and desorption over a wide temperature range, in particular in a higher temperature range of not lower than 700 °C and/or in a lower temperature range of not higher than 400 °C. The composite oxide contains oxygen, R composed of at least one of Ce and Pr, and Zr at a particular ratio, and optionally a particular ratio of M composed of at least one element selected from alkaline earth metals and the like. The composite oxide is free of a tetragonal crystal phase originated from zirconium oxide, and an electron diffraction pattern of the composite oxide appears as dotted diffraction spots. The composite oxide may be used as a co-catalyst for exhaust gas purifying catalysts, an oxygen reduction catalyst for fuel cells, and the like.