Cobalt Oxide Anodes for Chlorine Evolution
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Solution Overview
Problem
Existing electro-chlorination systems for water treatment and chlorine production face challenges due to the high cost and complexity of catalytic anodes coated with precious metals like iridium and ruthenium, which require efficient and durable alternatives for extended operation in industrial and municipal environments.
Innovation Solution
Development of catalytic anodes with a metallurgical catalyst layer comprising crystalline cobalt oxide particles in a matrix of tin and antimony, providing high selectivity and durability for the chlorine evolution reaction without the need for expensive precious metals, and a process involving specific stoichiometric ratios and heat treatment to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If precious metal coatings (iridium, ruthenium) are used on anodes to promote chlorine evolution reaction, then catalytic activity and selectivity are improved, but manufacturing cost and device complexity increase significantly
Solution Approach 1:
The invention changes the chemical composition parameters of the catalyst layer by replacing precious metals (iridium, ruthenium) with base metals (cobalt, nickel, manganese, zinc) in controlled ratios. The catalyst layer comprises 70-90 wt% metal oxides of base metals and 10-30 wt% conductive metal particles, creating a cost-effective alternative that maintains catalytic performance while reducing manufacturing complexity and cost.
Solution Approach 2:
The invention creates a composite catalyst layer structure combining base metal oxides (cobalt oxide, nickel oxide, manganese oxide, zinc oxide) with conductive metal particles (graphite, carbon black, or precious metal particles at reduced levels). This composite structure provides both catalytic activity for chlorine evolution and electrical conductivity, replacing the need for expensive pure precious metal coatings.
2Reliability
If precious metal coatings are applied to anodes to ensure durability for extended operation, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The invention replaces expensive precious metal coatings with cheaper base metal oxide-based catalyst layers. While base metals may have different longevity characteristics, the composite structure with conductive additives ensures sufficient durability for extended operation in electro-chlorination systems, achieving an acceptable service life at significantly reduced manufacturing cost.
Solution Approach 2:
The invention optimizes the compositional parameters of the catalyst layer by controlling the ratios of base metal oxides (70-90 wt%) to conductive additives (10-30 wt%). This parameter optimization ensures the catalyst layer maintains both catalytic activity and structural integrity during extended operation, providing reliable performance without requiring expensive precious metals.
3Device complexity
If base metal oxides are used instead of precious metals in catalyst layers, then manufacturing cost is reduced, but catalytic activity and selectivity for chlorine evolution may decrease
Solution Approach 1:
The invention creates a composite catalyst layer combining base metal oxides (cobalt oxide, nickel oxide, manganese oxide, zinc oxide) with conductive metal particles (graphite, carbon black, or reduced levels of precious metals). The base metal oxides provide catalytic sites for chlorine evolution while the conductive additives ensure adequate electrical conductivity and electron transfer, achieving both cost reduction and maintained catalytic activity.
Solution Approach 2:
The invention optimizes the compositional parameters by controlling the weight percentages of base metal oxides (70-90 wt%) and conductive additives (10-30 wt%). This parameter control ensures sufficient catalytic activity and selectivity for chlorine evolution reaction while using inexpensive base metals, achieving the desired balance between cost and performance.
4Device complexity
If the catalyst layer uses high proportions of base metals, then manufacturing cost decreases, but electrical conductivity of the anode may be insufficient
Solution Approach 1:
The invention creates a composite structure where base metal oxides (70-90 wt%) are combined with conductive metal particles (10-30 wt%). The conductive particles (graphite, carbon black, or small amounts of precious metals) form a conductive network within the catalyst layer, ensuring adequate electrical conductivity for efficient electron transfer during electro-chlorination while maintaining cost effectiveness through base metal usage.
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 cobalt oxide-based anodes demonstrate improved catalytic activity, selectivity, and resistance to acid, leading to efficient electrical operation at low over-potentials, extending the anode's lifetime and reducing costs compared to traditional precious metal-based anodes.
Implementation Method 1
an electrolytic cell that can operate efficiently for extended periods. To promote the generation of chlorine at the anode, it is common in the art to deploy catalytic coatings on the electrolyte-facing surface of the anode to catalyse the chlorine evolution reaction
Implementation Method 2
The chlorine evolution reaction ('CER') is a well-known reaction in industrial chemistry, which finds application in both the large-scale generation of chlorine for capture, and in the generation of chlorine for immediate applications. The chlor-alkali process generates chlorine and sodium hydroxide through the electrolysis of sodium chloride aqueous solutions
Data Source
AI summary
The present invention relates to catalytic anodes for use in electro-chlorination systems which generate chlorine from aqueous solutions via the chlorine evolution reaction. These anodes comprise an electrically conductive metallurgical catalyst layer essentially comprising crystalline cobalt oxide particles in a matrix of tin and antimony in a defined stoichiometry. The desired characteristics of this metallurgical layer may be realised via a process of preparation employing specific control of reactants and process conditions.