Elucidation of the different reaction mechanisms and pathways offered by the AOR

Project Information

EluMecAOR

Grant agreement ID: 101069017

DOI

10.3030/101069017

Project closed

EC signature date 1 August 2022

Start date 1 January 2023

End date 31 December 2024

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 173 847,36

Coordinated by

MAX-PLANCK-GESELLSCHAFT ZUR FORDERUNG DER WISSENSCHAFTEN EV
Germany

Periodic Reporting for period 1 - EluMecAOR (Elucidation of the different reaction mechanisms and pathways offered by the AOR)

Reporting period: 2023-01-01 to 2024-12-31

Summary of the context and overall objectives of the project

The European Union aspires to achieve a greenhouse gas-free economy by 2050.1 To meet this ambitious goal, green hydrogen is considered a pivotal energy source.2 One promising method for storing hydrogen involves using ammonia as a hydrogen carrier. At 8 bar, ammonia has more than twice the volumetric energy density (10.5 MJ/L) compared to compressed hydrogen at 700 bar (5 MJ/L).3 Furthermore, with the increasing production of green ammonia via the Haber-Bosch process coupled with renewable energy sources, it becomes a viable option for hydrogen production. Companies such as Siemens Energy, BP, and ThyssenKrupp are joining efforts to enhance ammonia production in countries with abundant renewable energy resources.4-7
Consequently, readily available ammonia emerges as an excellent candidate not only for hydrogen transport but also as a standalone energy source for fuel cells. For this reason, it is crucial to understand how to electrochemically decompose ammonia to generate electrical power.
The objective of this project is to elucidate the various descriptors and mechanisms governing the ammonia electro-oxidation reaction (AOR) and to identify the chemical species produced during this reaction. This knowledge will pave the way for designing efficient catalysts to harness energy from ammonia.

1. https://ec.europa.eu/clima/policies/strategies/2050_en
2. https://ec.europa.eu/energy/topics/energy-system-integration/hydrogen_es
3. Schüth, F.; Palkovits, R.; Schlögl, R.; Su, D. S. Ammonia as a possible element in an energy infrastructure: catalysts for ammonia decomposition. Energy Environ. Sci. 2012, 5, 6278
4. Lewis, J. Origin and MOL explore shipping green ammonia from Australia from 2026(www.upstreamonline.com) August 2021
5. Paul, S. BP sees potential for green hydrogen, ammonia plant in Australia (www.reuters.com) August 2021
6. https://www.siemens-energy.com/uk/en/offerings-uk/green-ammonia.html
7. https://www.thyssenkrupp-industrial-solutions.com/power-to-x/en/green-ammonia

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The EluMecAOR project conducted fundamental studies on the kinetics of AOR using potentiometric techniques across various temperatures. Efforts were also directed at enhancing the catalytic activity of the reaction through chemical modifications to the catalyst. Additionally, voltammetric and spectroscopic characterizations were performed under operational conditions (Raman and Q-EXAFS) to detect intermediates during the ammonia oxidation reaction.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The findings highlight the presence of key intermediates in AOR (NH2, *NO, and *N) and underscore the critical role of the solvent in reaction kinetics. Analysis of kinetic parameters, such as activation energy and pre-exponential factor, revealed that the solvation kinetics of ions play a crucial role in AOR, much like in reactions such as HER and ORR, where hydroxide ion solvation-(de)solvation affects catalytic performance. Specifically, in AOR, the results distinguish between poisonous species (*N and *NO) that arise in parallel mechanisms at different potentials under time-dependent dynamic conditions.
Furthermore, the results show how these poisonous species influence the reaction’s activation energy and the configurational entropy of the catalyst surface. The catalytic activity of AOR also depends on the catalyst's surface charge, which varies with pH.
From a fundamental perspective, this work is pivotal for developing and designing new catalysts with high activity, stability, and selectivity, enabling the use of ammonia as an energy source in fuel cells or for synthesizing high-value chemical compounds.