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This Week’s Discoveries | 23 October 2018

23 October 2018
This Week's Discoveries
Niels Bohrweg 2
2333 CA Leiden
De Sitterzaal



Suppressing the evolution of chlorine during salt water electrolysis using manganese oxide.


Jan Vos (LIC)
I am a fourth year PhD student in the group of Marc Koper, where we are focused on surface (electro)chemistry and electrochemical reactions related to sustainable energy storage and interconversion. My research concerns the electrocatalysis of the anode in electrolysis cells, an area containing one of the main bottlenecks that’s holding back widespread implementation of water electrolysis as a means of energy storage. I’m very passionate about all things catalysis; surface (electro)catalysis related to energy conversion and sustainability particularly gets me going. In my free time, I enjoy gaming, reading, and roaming the land on my road bike.


The electrolysis of water enables the ‘capture’ of solar or wind energy by converting electricity into chemical fuels. The use of seawater as feedstock is highly preferred over fresh water in this process, due to the scarcity of the latter and the high energy and capital cost of water desalination. Unfortunately, the presence of chloride ions in salt water may lead to the formation of toxic chlorine at the anode, a process which strongly competes with the preferred formation of oxygen from water molecules. Whereas oxygen is an environmentally friendly byproduct that can simply be discarded in the atmosphere, the unwanted formation of chlorine prohibits the use of saline water for practical electrolyzers.

In this work, we explore how a nanometer-thin layer of manganese oxide deposited on the anode was able to suppress the anodic formation of chlorine, favoring the principle of selective saline water splitting. We will show via fundamental surface studies that the mechanism by which manganese oxide promotes oxygen evolution is not so much a catalytic effect, but that the material simply acts as a physical barrier that prevents chloride ions from reacting at the electrode surface.


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