Iridium/Iridium Oxide pH Electrode with SPEEK/IL Sandwich Structure
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Solution Overview
Problem
In situ pH measurement in deep sea environments, particularly near hydrothermal vents, is challenging due to high pressure and the presence of redox substances, which cause potential drift in metal electrodes and result in inaccurate readings, as seen with Nafion electrodes that allow sulfide ions to interfere.
Innovation Solution
An iridium/iridium oxide electrode with a SPEEK/IL sandwich structure is developed, featuring two layers of SPEEK/SiOx/IL composite film and an outer SPEEK film, with an ionic liquid layer between each composite film layer and the electrode, enhancing proton conductivity and resistance to sulfide ion interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Nafion electrode is used to prevent redox substance permeation, then electrode protection is improved, but sulfide ion interference increases due to phase separation allowing smaller ions to pass through
Solution Approach 1:
The patent uses a composite film structure combining SPEEK (sulfonated polyether ether ketone) and ionic liquid (IL) materials. This composite structure leverages the narrow and tortuous permeation channels of SPEEK to block sulfide ions while maintaining proton conductivity through the ionic liquid component, thus preventing sulfide ion interference without compromising electrode protection.
Solution Approach 2:
The patent applies different functional properties to different parts of the film structure. The SPEEK component provides mechanical support and sulfide ion blocking through its narrow channels, while the ionic liquid component provides proton conductivity. This local differentiation of material functions resolves the contradiction between blocking harmful ions and maintaining necessary conductivity.
2Stability of the object's composition
If metal electrode is used for high temperature and pressure operation, then operational stability is improved, but potential drift occurs due to redox substance interaction
Solution Approach 1:
The patent introduces a composite film as an intermediary layer between the metal electrode and the sulfide ion-containing environment. This film acts as a selective barrier that prevents direct contact between redox substances and the electrode surface, thereby eliminating potential drift while maintaining operational stability in high temperature and pressure conditions.
Solution Approach 2:
The patent extracts the problematic interaction between metal electrodes and redox substances by placing a protective composite film between them. This separation removes the harmful chemical interaction while preserving the electrode's ability to function in high temperature and pressure environments.
3Measurement precision
If SPEEK film is used to resist sulfide ion interference, then measurement accuracy is improved, but proton conductivity may be reduced
Solution Approach 1:
The patent combines SPEEK with ionic liquid to create a composite film where SPEEK provides sulfide ion blocking through its narrow permeation channels, while the ionic liquid component compensates for any reduction in proton conductivity. The synergistic effect of this composite structure maintains both measurement accuracy and proton conductivity.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the film by incorporating ionic liquid into the SPEEK matrix. This changes the film's properties to maintain proton conductivity while preserving the sulfide ion blocking capability, thus resolving the contradiction between measurement accuracy and proton conductivity.
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 SPEEK/IL sandwich structure improves proton conductivity, reduces sulfide ion interference, and extends the electrode's service life, enabling accurate and stable pH detection in high-pressure, high-temperature environments.
Implementation Method 1
permeation channels inside the SPEEK film are narrower and more tortuous than those of the Nafion film. Accordingly, the SPEEK film can exhibit desirable resistance to sulfide ion interference
Implementation Method 2
An IL of the IL layer is [HOEtMIM][Cl] with a structural formula as follows. The IL has low volatility, strong conductivity, high viscosity, low vapor pressure, stable properties
Data Source
AI summary
An iridium/iridium oxide electrode for quantitatively detecting pH in a sulfide ion environment, and a preparation method and use thereof are provided. In the present disclosure, a sensitive layer of the iridium/iridium oxide electrode is coated with a sulfonated polyether ether ketone/ionic liquid (SPEEK/IL) sandwich structure. The SPEEK/IL sandwich structure includes two layers of SPEEK/SiOx/IL composite film and one layer of SPEEK film. The SPEEK film is arranged on an outermost layer. The SPEEK/IL sandwich structure covered on a surface of the electrode has an isolation effect on ions other than hydrogen ions, and especially shows a desirable isolation effect on sulfide ions with a smaller ion size. In this way, the electrode is not easily disturbed by redox substances in a complex aqueous environment.