Catalysts for the direct electrolysis of seawater

The deployment of renewable energy sources has accelerated in recent years, and consequently, one of their inherent challenges became increasingly relevant: The main sources of renewable energy, wind and solar, are intermittent in nature, and the production capacity therefore does not match the energy demand at all times. As a result, they are only base-load capable if the energy produced can be stored and reconverted again when needed. Apart from energy production, a complete decarbonization of society also implies that CO 2 free alternatives for industrial processes such as steel and cement production must be found. Hydrogen as an energy carrier can serve these purposes, and a general understanding has developed that green hydrogen production by means of water electrolysis will be a key technology to reach the above mentioned goals. Although alkaline water electrolysis has been commercialized since the early 20th century, efficiency is still a major shortcoming of this technology. The work presented herein is therefore concerned with the development of highly active, noble metal-free catalysts for alkaline electrolysis and, more generally, the efficient exploration of the associated chemical spaces using machine learning guided experimentation. The work conducted in the context of this thesis can be divided in three parts. In a first approach, a co-precipitation method was used to screen various combinations of single, binary and ternary metal hydroxides derived from eight different metals (Fe, Cr, Al, Co, Ni, Mn, Zn, Cu) with regard to their oxygen evolution reaction (OER) activity. The compounds are deposited directly onto Ni foam substrates, mimicking technical electrodes. Electrochemical tests were conducted in conventional and saline KOH to assess the suitability for direct seawater electrolysis. Samples containing Fe generally outperformed Fe free compositions, and NiFeCr showed the lowest overpotential of all samples with 247 mA cm −2 in 1 M KOH. OER activity was found largely similar between the two ...