Nomination of the Master Thesis by Marie Charlotte Neumann
for the European Materials Day 2023
Title: „Influence of (heat-controlled) High-Pressure Torsion (HPT) of Ni, Ni(OH)2, and Fe2O3 powder blends on catalysis and active phase formation for OER and HER“

It is our great pleasure to nominate the Master thesis of Marie Char-lotte Neumann (born: 25.05.1997 in Frankfurt am Main, Germany) for the European Materials Day 2023. The master thesis submitted by Ms. Marie Neumann is thematically related to the functional properties of nanocomposites prepared by high-pressure torsion and was con-ducted in a cooperation between Physical Metallurgy (Prof. K. Durst) and Surface Science (Prof. J. P. Hofmann) in the Department of Ma-terials and Geosciences at Technical University Darmstadt. The thesis can be considered as interdisciplinary, since a non-conventional pro-cessing route (HPT deformation of powders) was used to prepare a catalyst for water electrolysis and a quite wide and different spectrum of processing and characterization techniques was required to suc-cessfully complete the thesis. Furthermore, Marie was required to organize her work between two groups, which she very successfully managed and furthermore she is currently preparing a manuscript for an international journal based on the results of her thesis.
The thesis aimed at the preparation and spectroscopic as well as mi-croscopic characterization and electrochemical testing of Ni/Fe com-posite materials as catalysts for alkaline water electrolysis. One ques-tion was whether observations from recent literature on the influence of heterointerfaces on catalytic activity can also be represented by HPT processing and how a High-Pressure-Torsion (HPT) treatment of the Ni/Fe systems leads to a change of the electrochemical perfor-mance parameters with respect to the O2 and H2 evolution reactions in water electrolysis.
Ms. Neumann worked on this issue very systematically and carefully and prepared not only Ni + Fe2O3 HPT samples but also correspond-ing bulk and powder reference samples, including NiFe alloys. The HPT treatments were also investigated as a function of temperature. For material characterization, Ms. Neumann used metallurgical tech-niques such as Vickers hardness determination by indenter, scanning electron microscopy and roughness determination. Raman and XPS were used for spectroscopic characterization. ICP-OES was per-formed on the electrolytes used to measure leaching from the elec-trodes. A selection of samples was examined microscopically before and after electrocatalysis to identify morphological changes. These were then also compared with evaluation of roughness and electro-chemical surface area (by double layer capacitance measurements). The HPT treatments resulted in a strong grain refinement and inter-mixing of the powders with a strongly increase interfacial area, which also had an influence on the OER in the case of powder samples. Interestingly, Ms. Neumann was able to show that regardless of whether alloy or Ni/Fe powder mixtures were used, the OER activity behaved very similarly, which she attributed to the formation of a simi-lar catalytically active phase. Introduction of iron was found with posi-tive effect on OER catalysis. Increasing the phase boundaries be-tween Fe and Ni containing oxide induced by HPT treatment also had a positive effect on catalysis.
In the thesis, the scientific background of the work is thematically very well introduced including a good overview of the problem, the neces-sary concepts of HPT treatment and electrocatalysis. This is followed by a concise presentation of the characterization methods used. Overall, the work is of a very good scientific, linguistic and design lev-el. The results obtained are carefully prepared, described and dis-cussed. The underlying experiments systematically and carefully per-formed including discussion of the validity of the data.
Overall, it can be said that Ms. Neumann carried out and coordinated a complex and extensive experimental work in two fields. Her working method was very systematic and independent, and Ms. Neumann was able to cover the complete process chain up to the evaluation of the catalytic properties of her composites on several material sys-tems. With her presentation on 14.02.2023, Marie Neumann was able to demonstrate a sound knowledge and understanding of the funda-mentals of the work in presentation, discussion and defence of the results.
Besides her scientific work, Marie Neumann has also been a very active materials science student, being a student member of the Ma-terials Science Exam committee (2021-2022), the faculty council (2019-2021),several search committees as well as actively organizing the 22. KaWuM (Konferenz aller werkstofftechnischen und material-wissenschaftlichen Studiengänge) in Nov. 2021. She has been co-organizing the 2023 summer school of the CRC 1548 FLAIR (Fermi level engineering of electroceramic oxides), where she is currently working as a PhD student.
Darmstadt, 29.09.2023


Prof. Dr.-Ing. Karsten Durst         Prof. Dr. rer. nat. Jan Philipp Hofmann