Chlorine Electrode Catalyst Composition for Polarity Switching
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Solution Overview
Problem
Existing chlorine-generating electrodes for dilute salt water, such as tap water, face challenges in achieving high chlorine generation efficiency and long service life when polarity is switched at short intervals at a relatively high current density, particularly in domestic appliances where size reduction is necessary.
Innovation Solution
A chlorine-generating electrode with a catalyst layer composed of 2 to 24 mol% platinum, 41 to 49 mol% iridium oxide, and 35 to 49 mol% tantalum oxide, formed on a titanium or titanium-based alloy substrate with a porous platinum coating and titanium oxide intermediate layer, designed for polarity switching every 5 to 60 seconds at a current density of 0.05 to 0.25 A·cm−2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a porous platinum coating layer on a titanium substrate with a composite catalyst layer (30-65 mol% iridium oxide, 10-40 mol% tantalum oxide, 25-60 mol% platinum) is used, then chlorine generation efficiency is improved and stability during acid washing is improved, but service life under frequent polarity switching at high current density deteriorates
Solution Approach 1:
The patent changes the compositional parameters of the catalyst layer, specifically adjusting the mol% ratios of iridium oxide (41-49 mol%), tantalum oxide (35-49 mol%), and platinum (2-24 mol%). This parameter optimization resolves the contradiction by finding a composition that balances chlorine generation efficiency with durability under polarity switching conditions.
Solution Approach 2:
The patent uses a composite catalyst layer combining three materials (iridium oxide, tantalum oxide, and platinum) in specific proportions. This composite structure leverages the complementary properties of each material: iridium oxide for stability, tantalum oxide for durability under polarity switching, and platinum for catalytic activity, thereby resolving the service life issue while maintaining efficiency.
2Ease of operation
If polarity is switched at short intervals at high current density to remove scale and enable maintenance-free operation, then ease of operation is improved, but service life of the electrode deteriorates
Solution Approach 1:
The patent optimizes the compositional parameters of the catalyst layer, particularly increasing tantalum oxide content (35-49 mol%) which provides exceptional stability under polarity switching conditions. This allows the electrode to withstand frequent polarity reversals required for maintenance-free operation without degrading.
Solution Approach 2:
The electrode enables self-maintenance through automatic polarity switching that removes scale deposits from the cathode surface during normal operation. The optimized catalyst layer composition ensures this self-cleaning process does not compromise the electrode's service life.
3Volume of moving object
If electrode distance is reduced to 2 mm or less to reduce apparatus size for domestic appliance installation, then device complexity is reduced and compactness is improved, but current density requirements increase leading to faster electrode degradation
Solution Approach 1:
The patent optimizes the catalyst layer composition with specific mol% ranges of iridium oxide (41-49%), tantalum oxide (35-49%), and platinum (2-24%). This composition enables the electrode to operate at high current densities required for compact 2 mm electrode spacing while maintaining service life through enhanced stability and resistance to degradation.
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 electrode achieves high chlorine generation efficiency and extended service life, outperforming previous designs by maintaining efficiency and durability under conditions of frequent polarity switching at high current density.
Implementation Method 1
generate chlorine by electrolyzing dilute salt water while repeatedly switching the polarity of an anode and a cathode every 5 to 60 seconds at a current density of 0.05 to 0.25 A·cm−2
Implementation Method 2
the catalyst layer consists of 2 mol % to 24 mol % of platinum, 41 mol % to 49 mol % of iridium oxide, and 35 mol % to 49 mol % of tantalum oxide in terms of metal amount
Data Source
AI summary
Disclosed herein are an electrode for generating chlorine comprising in sequence a substrate consisting of titanium or titanium-based alloy, an intermediate layer, and a catalyst layer, and a method for generating chlorine by electrolyzing dilute salt water in an electrolytic cell comprising at least a pair of said electrodes with an anode and a cathode. The intermediate layer comprises a porous platinum coating and titanium oxide provided on the substrate, the catalyst layer, in particular, consists of 2 mol % to 24 mol % platinum, 41 mol % to 49 mol % iridium oxide, and 35 mol % to 49 mol % tantalum oxide in metal equivalent. The electrode and the method with high chlorine generation efficiency and longer life time are provided under the condition of electrolyzing dilute salt water while repeatedly switching the polarity of anode and cathode every 5 to 60 seconds at a current density of 0.05 to 0.25 A·cm−2.