Speakers
Description
As a promising chemical storage medium for hydrogen, the thermal decomposition of ammonia using non-precious metal catalysts, such as Co, Ni, and Fe, has recently gained significant attention. In our work, we are exploring new avenues for the synthesis of such catalysts. We prepare nanostructured oxide precursors that contain both the active element and potential promoters in their crystal structure and generate metal nanoparticles that exhibit exceptional metal-support/promoter interactions by exsolution during reductive pretreatment or under operation conditions. We have chosen spray-flame synthesis (SFS) and continuous-flow hydrothermal synthesis (CFHS) as preparation methods for the oxide precursors, as nanoparticles can be obtained continuously. With regard to the crystal structures of the precursors, we focus on rock salt structures,1 spinels2 and perovskites. In order to be able to compare the properties of the catalysts with those of the materials prepared and tested by the collaborating partners in the project, cross-laboratory standard operating procedures were developed, the tests were automated and integrated into the data infrastructure of our institute, and the compatibility of the data structure with overarching databases was adapted.3
An important result of the project is that both the precursor structure and the synthesis method have a significant influence on the catalytic activity. In particular, catalysts derived from perovskites and spinels with general composition LaₓSr₁₋ₓCoO₃ and La2O3-CoₓNi₁₋ₓAl₂O₄ show exceptionally high activities at 500°C of 0.0423 mmol·gcat⁻¹·s⁻¹ and 0.0356 mmol·gcat⁻¹·s⁻¹, respectively, which exceed those of benchmark catalysts. Complementary operando and in situ spectroscopic and analytical methods such as X-ray diffraction, vibrational spectroscopy, NAP-XPS and electron microscopy were applied to elucidate particle size effects and the influence of promoters on catalytic properties. The function of basic promoters will be discussed.
1. Alkan, B. et al., From “Single Sites” to Stable Nanoparticles Derived from Spray-Flame Synthesized Solid Solutions of Cobalt in MgO for Ammonia Decomposition, to be submitted (2024).
2. Ngo, A. B. et al., Continuous Flow Hydrothermal Synthesis (CFHS) of Mg-doped Co Spinels under Supercritical Conditions, to be submitted (2024).
3. Moshantaf, A. et al., Advancing Catalysis Research through FAIR Data Principles Implemented in a Local Data Infrastructure – A Case Study of an Automated Test Reactor. DOI: 10.1039/D4CY00693C (2024).
