Methodology development for SO2 crossover mitigation in sulphur dioxide depolarized electrolyzer

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master_Iyer_Raghavendra_2024.pdf (2.67 MB)

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Insinööritieteiden korkeakoulu | Master's thesis
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Date

2024-08-19

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Major/Subject

Sustainable Energy Conversion Processes

Mcode

ENG3069

Degree programme

Master's Programme in Advanced Energy Solutions (AAE)

Language

en

Pages

72

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Abstract

Renewable hydrogen plays a key role in the ongoing energy transition, and water electrolysis is employed for its generation using the proton exchange membrane (PEM) electrolyzer. However, this technology requires high overpotentials and uses expensive platinum group metal catalysts, limiting their suitability for large-scale hydrogen production. An alternative to the PEM technology is the SO2 depolarized electrolyzer (SDE), which uses SO2 at the anode and requires less energy (E° = 0.16 V) compared to PEM electrolyzer (E° = 1.23 V). However, the SDE faces the issue of SO2 crossover, causing the formation of parasitic products such as sulphur and H2S at the cathode. This thesis details the building of an improved setup and the associated troubleshooting performed during setup construction. The significance of the bichromatometry titration technique is elucidated and the technique was also optimized, highlighting the influence of the solution’s H2SO4 concentration on titration accuracy. Further, a standard operational protocol is established for the SDE, with its performance being analyzed by monitoring various parameters such as current, SO2 concentration, electrolyte concentration, volume of product gas, and gas purity. Graphite, and gold on Vulcan coatings were prepared on the membrane and tested to study their potency in reducing SO2 crossover. The results indicated the potential of such coatings in aiding the reduction of SO2 crossover and the need for further optimization to improve their efficacy. The scope of future work involves further optimization of the bichromatometry titration, utilizing a better designed electrolysis cell with a lower surface area to study the SO2 crossover effect and optimize membrane coatings, and performing long-duration electrolysis to assess the performance of the system and its stability.

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Supervisor

Santasalo-Aarnio, Annukka

Thesis advisor

Narayana Prasad, Pragya

Keywords

sulphur dioxide depolarized electrolyzer, SO2 crossover, bichromatometry titration, gas purity, membrane electrode assemblies

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https://urn.fi/URN:NBN:fi:aalto-202408255705

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[dipl] Insinööritieteiden korkeakoulu / ENG