Halogen-Doped Tin Oxide Particles for Fuel Cell Electrodes
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Solution Overview
Problem
Halogen-containing tin oxide particles tend to elute in acidic environments, limiting their acid resistance and stability in applications such as fuel cells.
Innovation Solution
Producing halogen-containing tin oxide particles through a method involving neutralization of a halogen-containing aqueous solution with an alkali, oxidation of the precursor, and subsequent hydrothermal treatment under high-temperature-high-pressure conditions (270°C or higher and 20 MPa or higher) to enhance acid resistance and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If halogen-containing tin oxide is produced by conventional methods (contact with fluorine gas or hydrothermal treatment at lower conditions), then conductivity is improved, but acid resistance deteriorates due to halogen elution
Solution Approach 1:
The invention changes the production parameters by performing hydrothermal treatment at extremely high temperature (270°C or higher) and high pressure (20 MPa or higher). This parameter change transforms the tin oxide precursor into a crystal structure where halogen is strongly bonded, preventing elution in acidic environments while maintaining conductivity
Solution Approach 2:
The invention creates a composite structure within the tin oxide particles by forming a core-shell like structure where the inner core contains strongly bonded halogen-substituted tin oxide crystals formed under high temperature-high pressure conditions, while the outer layer maintains conductivity. This composite approach ensures both acid resistance and electrical conductivity
2Reliability
If conventional hydrothermal treatment is performed at lower temperature and pressure, then production cost and energy consumption are reduced, but acid resistance deteriorates
Solution Approach 1:
The invention dramatically increases the temperature parameter to 270°C or higher and pressure to 20 MPa or higher during hydrothermal treatment. This parameter change is necessary to form the highly acid-resistant halogen-substituted tin oxide crystal structure, accepting higher energy consumption as a trade-off for achieving superior acid resistance
3Object-affected harmful factors
If halogen is used as dopant instead of antimony, then environmental load is reduced, but acid resistance deteriorates due to halogen elution
Solution Approach 1:
The invention uses high temperature (270°C or higher) and high pressure (20 MPa or higher) hydrothermal treatment to transform the halogen-doped tin oxide into a stable crystal structure. This parameter change enables halogen to be strongly incorporated into the crystal lattice, preventing elution and achieving acid resistance while maintaining the environmental benefits of using halogen instead of antimony
Solution Approach 2:
The invention creates a stable composite structure where halogen is strongly bonded within the tin oxide crystal matrix formed under high temperature-high pressure conditions. This composite approach maintains the environmental advantages of halogen doping while achieving the acid resistance typically associated with more stable dopants
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 particles exhibit high acid resistance, improved conductivity, and reduced halogen elution, making them suitable for use in transparent conductive films, fuel cell electrodes, and infrared shielding applications.
Implementation Method 1
neutralizing a halogen-containing aqueous solution containing a divalent tin compound with an alkali to form a slurry containing a tin oxide precursor
Implementation Method 2
oxidizing the precursor
Implementation Method 3
performing hydrothermal treatment on the slurry containing the oxidized precursor under a high-temperature-high-pressure condition in which a temperature is 270°C or higher and pressure is 20 MPa or higher
Data Source
Figure 1
AI summary
These halogen-containing tin oxide particles have a BET specific surface area of 25 - 100 m2/g and a crystallite diameter of 8 - 30 nm. The particles optimally contain 0.01 - 0.75 mass% halogen. Fluoline is optimally cantained as the halogen. Optimally, the particles additionally contain tantalum, niobium, phosphorus, antimony, tungsten, or molybdenum. The volume resistivity is optimally 0.1 - 1000 Ω·cm.