ICRC 2024 - Session 3

Dr. Till Frömling, Fraunhofer IWK

Dr. Andreas Brumby, Materials Valley e.V.

Dr. Marc Widenmeyer, Technische Universität Darmstadt

For the energy transition we aim to dispel fossil fuels from our society. In order to enable this, renewable energies are important to fill the related energy gap. In this respect electrochemistry offers several solutions for energy storage and conversion by the use of (super-)capacitors, batteries as well as electrocatalysis in fuel cells and electrolysers (H2 and CO2). In several of such devices critical raw materials are used, like platinum in fuel cells and iridium and platinum in hydrogen electrolysers. If we would like to become sustainable in a general perspective, it is necessary to not only develop sustainable technologies but also using earth abundant elements to replace precious group metal catalysts. In proton exchange fuel cells (PEFCs), iron nitrogen carbon (FeNC) catalysts reach similar activities but still need to be improved in terms of durability in comparison to platinum.[1] From its chemistry iron by itself would not be stable under PEFC operation. However, induced by nitrogen ligands, the iron is stabilized making it applicable even in PEFCs. This illustrates the importance of the local environment on the reactivity of iron.[2-5]In our CRC Iron, upgraded! we use this approach and explore systematically,[6] how the local environment changes the properties associated with iron aiming for structure-property maps for different fields of application and to deduce general trends in chemistry.In this work, I will introduce the concept of our CRC towards a sustainable materials database and highlight some of the results for the FeNC catalysts.

Climate-neutral hydrogen plays an important role on the path to a climate-neutral society, including as a raw material for the petrochemical industry, as a reducing agent in the production of steel and other metals and as a clean energy source. Although the technological foundations were laid a long time ago, many technologies are not yet fully developed and therefore not yet competitive. In his presentation, Steffen Hasenzahl will focus on the development and scaling of membranes for the next generation of electrolyzers, the provision of cost-effective electrocatalysts and the use of high-performance plastics for the transportation of hydrogen.

Hydrogen is widely discussed as the prime future energy carrier in terms of gravimetric energy density and availability through water splitting, but inherent limitations in efficient storage and transportation capabilities limit a widespread technology rollout. Moreover, green alternatives for hydrogen production apart from electrolysis based on renewable energies must be established to diversify the production landscape for increased security of supply and decentralized logistics. Apart from thermochemical cycles and biological hydrogen production direct conversion of solar energy to chemical energy in photochemical or photoelectrochemical systems are seen as viable and scalable technologies. Efficient photocatalysts providing high photocurrents at low overpotentials with inherent stability combined with raw material availability are of key importance to establish this technology as a feasible addition in the growing hydrogen economy. The presentation will review current advances in the development of catalysts for photoelectrochemical water splitting reactions and highlight the technological potential as well as limitations in terms of scalability and resource demands.

The EU Commission proposed in March 2023 the ECRMA (European Critical Raw Materials Act). Andreas will give a short introduction on the ECRMA and discusses the implications especially for the emerging Hydrogen Economy, e.g. for electrolysis development. He will also mention the PFAS (Per- and polyfluoroalkyl substances) legislation process and by this stressing the necessity of "supply chain thinking".

Ammonia borane (AB) has a rich history in the realm of chemical hydrogen storage. Discovered in the mid-20th century, it was re-discovered in the early 21st century and has been extensively studied in the past two decades. AB naturally stores 19.5 wt% of hydrogen and can release >67% of it when heated to 200 °C. This release can occur below 100 °C when AB is destabilized, for example, through nanoconfinement.

AB has also paved the way for various BN(C)H compounds, often derived from it. Examples of these derivatives include metal amidoboranes, hydrazine borane, alkylamine boranes, as well as boron nitride (pure or carbon-doped) and borocarbonitride. Remarkably, all of these compounds have, at one point or another, been considered for chemical or physical hydrogen storage.

In our group, we have explored these derivatives. Initially, our focus was on their role as hydrogen carriers, particularly in the case of hydrides. Subsequently, we investigated their potential for physical hydrogen storage, emphasizing boron nitride-based porous systems. Recently, we have observed that some exhibit the potential to capture gases beyond hydrogen, sparking new interests in gas capture, hydrogen separation/purification. The upcoming ICRC 2024 meeting will provide an excellent opportunity to showcase our latest achievements.