Graphite Anodes with Oxide Coatings for Low-Overpotential Chlorine Evolution

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Solution Overview

Problem

Existing graphite anodes in molten halide systems face high anodic overpotential, leading to increased energy consumption and environmental issues such as CO2 and perfluorocarbon emissions, making them unsuitable for efficient chlorine gas production and metal recovery processes.

Innovation Solution

Development of a dimensionally stable anode using a graphite substrate coated with transition metal oxides like RuO2, which reduces overpotential and enables efficient chlorine gas evolution in chloride molten salt electrolysis, allowing for the co-production of metals and chlorine gas with minimal environmental impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If graphite anodes are used in molten halide systems, then the anode structure is simple and mechanically stable, but the anodic overpotential is high leading to increased energy consumption

Engineering Contradiction:

Improveanode structureVSAvoidenergy consumption

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent applies composite materials by combining transition metal oxides (such as RuO2, IrO2, or their mixtures) with graphite to form a coated anode structure. The transition metal oxide coating (1-100 micrometers thick) is applied onto the graphite substrate, creating a composite electrode that maintains the mechanical stability of graphite while introducing the electrocatalytic properties of transition metal oxides to reduce anodic overpotential for chlorine evolution.

Inventive Principle:

Principle #40Composite materials

2Productivity

If graphite anodes are used in fluoride-containing electrolytes, then the electrolysis process can proceed, but harmful perfluorocarbon emissions are generated

Engineering Contradiction:

Improveelectrolysis processVSAvoidperfluorocarbon emissions

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful interaction between graphite and fluoride-containing electrolytes that produces perfluorocarbon emissions into a beneficial process by introducing transition metal oxide coatings. These coatings act as a barrier and catalytic surface that promotes chlorine evolution while suppressing the formation of harmful perfluorocarbons, thus eliminating the environmental malignity while maintaining electrolysis productivity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Use of energy by moving object

If transition metal oxides are used as coated anodes, then the overpotential for chlorine gas evolution is reduced, but the anode fabrication becomes mechanically difficult

Engineering Contradiction:

Improveoverpotential for chlorine evolutionVSAvoidanode fabrication

Core Design Contradiction:

Use of energy by moving objectVSEase of manufacture

Solution Approach 1:

The patent uses graphite as an intermediary substrate that mediates between the transition metal oxide coating and the electrolysis process. The graphite substrate provides mechanical stability and ease of fabrication, while the transition metal oxide coating (applied via techniques like screen printing, spray drying, or dip-coating) provides the electrocatalytic function. This intermediary approach allows the transition metal oxide to be handled in a mechanically robust form factor.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Productivity

If conventional fluoride-based molten salt electrolysis is used for rare earth metal production, then metal production can be achieved, but harmful CO2 and PFC emissions and high energy consumption occur

Engineering Contradiction:

Improvemetal productionVSAvoidenvironmental malignity

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by modifying the electrochemical parameters at the anode surface through transition metal oxide coating. This changes the reaction pathway and reduces the overpotential for chlorine evolution, thereby lowering the cell voltage and energy consumption. Simultaneously, the coating suppresses harmful side reactions that produce CO2 and PFC emissions, achieving sustainable metal production.

Inventive Principle:

Principle #35Parameter changes

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 anode achieves low chlorine evolution potential, suppresses side reactions, and enables continuous production of metals and chlorine gas with reduced energy consumption and minimal emissions, facilitating sustainable metal recovery processes.

Implementation Method 1

transition metal oxide coated anodes, such as ruthenium dioxide (RuO2) coated anodes, are catalytic to and reduce the overpotential for electrolytic chlorine gas evolution

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

electrolytic chlorine gas evolution in chloride molten salt electrolysis

Methodology Applied

Scientific EffectElectrolysis: Electrolysis

Data Source

PatentUS12378684B2Dimensionally stable anode for electrolytic chlorine evolution in molten salts

Publication Date: 2025.08.05 CASE WESTERN RESERVE UNIV

AI summary

An anode for electrolytic chlorine evolution in a molten salt electrolyte includes a graphite substrate and a coating including a transition metal oxide disposed on at least a portion of the substrate.