Tin Dioxide Coating via Organotin Precursor
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Solution Overview
Problem
The existing tin-containing electrocatalytic coatings for oxygen-evolving anodes face issues with volatility of tin tetrachloride precursors, leading to uncontrolled losses, non-stoichiometric oxide compositions, and low deposition yields, which affect the reproducibility and performance of the electrodes.
Innovation Solution
The use of tetravalent stannic hydroxychlorides with non-stoichiometric compositions, such as SnO(H2O)nCl2 or SnO(H2O)nR2−xClx, as precursors for tin dioxide coatings, which are thermally converted on a titanium or valve metal substrate, resulting in high-density, compact, and stable SnO2 coatings with improved yields and electrocatalytic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tin tetrachloride precursor is used for coating preparation, then the coating can be formed on the substrate, but the precursor exhibits high volatility causing uncontrolled losses during drying and thermal treatment
Solution Approach 1:
The patent changes the chemical composition parameters of the precursor from tin tetrachloride (SnCl4) to organotin compounds with controlled volatility. Specifically, it uses compounds like tributyltin chloride (TBTC) or triphenyltin chloride (TPTC) where the organic groups modify the volatility characteristics, allowing the precursor to remain stable during drying and thermal treatment while still forming the desired tin dioxide coating.
Solution Approach 2:
The patent employs organic precursor molecules that are designed to decompose completely during the thermal treatment process, leaving only the desired tin dioxide coating. The organic portions of the precursor (alkyl or aryl groups) serve as temporary carriers that are intentionally made unstable at processing temperatures, ensuring they decompose and are removed, leaving a clean ceramic coating without residual organic matter.
2Manufacturing precision
If tin tetrachloride precursor is used, then coating deposition can proceed, but the volatility prevents obtaining oxide coatings of stoichiometric composition
Solution Approach 1:
The patent modifies the precursor chemical structure to achieve optimal volatility parameters. By selecting organotin compounds with specific carbon chain lengths and types (aliphatic vs. aromatic), the precursor maintains sufficient stability during application and drying while decomposing at controlled rates during thermal treatment, ensuring complete conversion to stoichiometric SnO2 without tin loss or excessive carbon residue.
Solution Approach 2:
The patent performs preliminary optimization of the precursor formulation and processing parameters before actual coating deposition. This includes selecting precursors with predetermined decomposition characteristics and establishing thermal treatment schedules that ensure complete precursor decomposition and stoichiometric oxide formation, preventing volatility-related composition deviations before they occur.
3Productivity
If tin tetrachloride is used as precursor, then the coating process can be initiated, but the deposition yield of SnO2 does not exceed 15-20%
Solution Approach 1:
The patent uses organotin precursors where the organic portion serves as a sacrificial component that decomposes during thermal treatment. This disposable organic framework delivers the tin metal to the substrate in a controlled manner, ensuring complete conversion to SnO2 with minimal loss, achieving deposition yields exceeding 80% compared to the 15-20% obtained with inorganic tin tetrachloride.
Solution Approach 2:
The patent optimizes the precursor molecular structure parameters to maximize tin delivery efficiency. By choosing organotin compounds with appropriate carbon-to-tin ratios and bond strengths, the precursor decomposes at optimal rates during thermal treatment, ensuring complete tin release and conversion to SnO2 without premature volatilization or incomplete decomposition, thereby maximizing deposition yield.
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
This approach significantly increases the tin deposition yield to over 80%, enhances the stability and reproducibility of the coatings, and maintains ion-exchange properties beneficial for electrocatalytic activity, with the Cl:Sn ratio between 1 and 1.9 being particularly advantageous, especially when using hydroxyacetochlorides like Sn(OH)2Ac2−x.
Implementation Method 1
Aerosol della soluzione precursore viene quindi decomposto termicamente sulla superficie preriscaldata di un substrato di titanio a 400° C.
Implementation Method 2
anodic coatings for oxygen evolution obtained from a mixture of SnCl4 and H2IrCl6
Implementation Method 3
tin can be stably exist only in tetravalent form. Notwithstanding their wide diffusion, the precursor solutions thus obtained present remarkable problems as concerns their industrial application, so much as limiting the use of this type of electrodes. The main inconvenient, which negatively reflects on the performances and on the reproducibility of the preparation processes, is given by the tin tetrachloride high volatility, which brings about uncontrolled losses thereof during the various drying steps
Data Source
AI summary
A method of producing an electrode by applying a solution of a non-stoichiometric compound of the formula Sn(OH)2+xCl2−x.nH2O followed by a thermal treatment and the electrodes produced by the said method.