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Selectivity and gas composition in electrochemical systems by mass spectrometry

Time: Fri 2024-05-24 13.00

Location: E3, Osquars backe 14, Stockholm

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Language: English

Subject area: Chemical Engineering

Doctoral student: Aleksandra Lindberg , Tillämpad elektrokemi

Opponent: Associate Professor Thijs de Groot, Eindhoven University of Technology, Nederländerna

Supervisor: Professor Göran Lindbergh, Tillämpad elektrokemi; Ann Cornell Ann M. Cornell, Tillämpad elektrokemi; Susanne Holmin, Permascand AB

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QC 20240418


This doctoral thesis presents experimental studies of gaseous products of two electrochemical systems: the chlorate process and the nickel-metal hydride (NiMH) battery, employing mass spectrometry.

The cathodic efficiency for the hydrogen evolution reaction (HER) of the chlorate process was investigated by employing ex-situ synthesized MnOx electrodes. Without the addition of toxic chromium (VI), used today in industry, high cathodic efficiency was achieved. The effect of different annealing temperatures in the electrode preparation on HER efficiency was examined. The addition of 1000 times lower concentrations of chromium (VI) than used in the industry today, together with in-situ added molybdate,showed promising results in keeping high cathodic efficiency and selectivity towards HER. The evolution of oxygen decreases anodic efficiency and also presents a safety risk due to simultaneously proceeding of HER in the undivided cell. The amount of produced oxygen by two types of electrodes TiRu and TiRuSnSb, was followed. Oxygen is produced by homogenous hypochlorite decomposition, heterogeneously by different electrode surface present in the electrolyte solution and anodically during the electrolysis i.e. electrochemically.

Investigating gas composition in batteries presents a challenge due to the complexity of reactions leading to the gas evolution.Additionally, the gas consumption has a significant impact on the amount and constituents of the collected gases. The methodology for investigating gas composition of the NiMH battery without influencing the battery performance was established. Two technologies, sampler and microcapillary, gave reasonable and complementing results.