RuO2-SnO2-Ir Anode Coating for Chlorine Evolution
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Solution Overview
Problem
Existing electrodes for chlorine evolution in chlor-alkali cells suffer from suboptimal chlorine overvoltage and contamination with oxygen, leading to inefficient chlorine production and increased energy consumption, especially at high current densities, which affects the purity and usability of chlorine in industrial applications.
Innovation Solution
A tin-based catalytic coating with a specific composition and structure, comprising 55-70% tin, 5-20% iridium, and 20-40% ruthenium oxides, applied in layers of controlled thickness and noble metal loading, is used on a metal substrate to enhance chlorine evolution selectivity and reduce electrode wear, with an intermediate heat treatment step to further decrease oxygen contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a catalyst based on RuO2 mixed with TiO2 is used, then the overvoltage of anodic chlorine evolution is reduced, but the overvoltage is not yet optimal and energy consumption is increased
Solution Approach 1:
The invention changes the chemical composition parameters of the catalyst by replacing TiO2 with SnO2 and adding specific amounts of noble metals (Ir and/or Pt), thereby optimizing the catalytic properties and reducing both chlorine overvoltage and energy consumption simultaneously
Solution Approach 2:
The invention uses a composite catalyst material consisting of RuO2 mixed with SnO2 and supplemented with noble metals (Ir and/or Pt), combining the advantages of different materials to achieve optimal chlorine evolution performance with reduced energy consumption
2Reliability
If a second noble metal (Ir or Pt) is added to a RuO2-SnO2 formulation, then chlorine overvoltage is reduced, but oxygen evolution reaction overvoltage is also lowered causing excessive oxygen contamination
Solution Approach 1:
The invention precisely controls the composition parameters by limiting Ir content to 0.1-5% and Pt content to 0.1-5%, and optimizing the RuO2-SnO2 base composition, thereby achieving sufficient chlorine evolution efficiency while minimizing oxygen evolution and contamination
Solution Approach 2:
The invention creates a catalyst with non-uniform composition characteristics by combining RuO2, SnO2, and small amounts of noble metals in specific proportions, where each component contributes differently to chlorine and oxygen evolution reactions, achieving selective catalysis
3Object-generated harmful factors
If critical amounts of Pd and Nb are added, then oxygen contamination is partially mitigated, but at high current densities the purity level of product chlorine is still far from the minimum target
Solution Approach 1:
The invention changes the catalyst composition parameters by using RuO2-SnO2 as the base with controlled additions of Ir (0.1-5%) and/or Pt (0.1-5%), achieving superior chlorine purity (>99.5%) at high current densities compared to Pd-Nb formulations
Solution Approach 2:
The invention employs a composite catalyst system of RuO2-SnO2-Ir and/or Pt that works synergistically to provide both high chlorine evolution efficiency and high selectivity, achieving chlorine purity levels that exceed industry requirements even at high current densities
4Productivity
If alternating layers of tin oxides and titanium oxides are applied, then process performance is partially improved, but the invention provides a more optimized solution with specific noble metal loading
Solution Approach 1:
The invention optimizes the catalyst formulation by precisely controlling the composition ratios of RuO2, SnO2, and noble metals (Ir and/or Pt), achieving enhanced chlorine evolution performance without requiring complex alternating layer structures
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 proposed electrode achieves improved cell voltage, selectivity of chlorine over oxygen production, and reduced noble metal consumption, leading to more efficient and longer-lasting chlorine production with higher purity, addressing the limitations of prior art.
Implementation Method 1
The electrolysis of alkali chloride brines, such as sodium chloride brine for the production of chlorine and caustic soda
Implementation Method 2
anodes based on titanium or other valve metals activated with a superficial layer of ruthenium dioxide (RuO2) which has the property of lowering the overvoltage of the anodic chlorine evolution reaction
Data Source
AI summary
An electrode suitable as chlorine-evolving anode in electrolytic cells and a method for obtaining thereof is provided. The electrode has a metal substrate coated with a catalytic composition made of thin layers based on oxides of tin, iridium and ruthenium and combines excellent characteristics of anodic potential and selectivity with respect to the reaction of chlorine evolution without resorting to the use of dopants such as platinum and palladium.