Cobalt/Manganese Catalysts for the Oxygen Evolution Reaction

In order to reduce the CO2 emissions, it is necessary to scale down the dependency on fossil fuels such as oil or natural gas. However, alternative renewable energy sources such as wind or solar power are problematic too: they do not generate power continuously, but rather intermittently (e.g. there is no wind power in still air). Since the need for power is present all the time, the excess energy produced has to be stored. One way to achieve this is to split water into its elements, hydrogen and oxygen, via electrolysis. The generated hydrogen can subsequently be used as an energy storage, which can either be transformed back to electrical power, or be used as feed stock in the chemical industry to produce other materials (nowadays, most of the hydrogen used there originates from fossil fuels as well). Unfortunately, the water splitting process is inefficient since the formation of oxygen (oxygen evolution reaction) is very sluggish and thus hampers the whole reaction, leading to more energy being required to perform the splitting, rendering this process infeasible. The solution is to use catalysts for the oxygen evolution reaction, which can lower the energy requirements and consequently speed up the reaction. However, most of the conventional catalysts consist of noble metals (such as platinum), which are very expensive. This is why there are attempts to replace them by cheaper materials such as cobalt or manganese. Even though it is known that cobalt- and manganese-containing materials can be better catalysts than precious metals, it is not yet clear why they work so well. The goal of this project is to discern the mechanisms of the oxygen evolution reaction on cobalt and manganese catalysts. To achieve this, state-of-the-art techniques such as X-ray spectroscopy or electron microscopy will be used to investigate the catalysts during their operation. With these experiments, chemical changes, such as the formation of transition states, which lower the energy requirements, can be followed in order to determine the reaction pathways. In turn, this knowledge will be of use to design even better catalysts.