Synchrotron-based study of Ir model catalysts during operando ammonia oxidation

• Applicant: Fernando García Martinez, Ph.D.
• Subject Area: Solid State and Surface Chemistry, Material Synthesis
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 574114707

This proposal aims to advance understanding of the surface chemistry of iridium (Ir) catalysts during the operando ammonia (NH₃) oxidation reaction by oxygen (O₂). Gaining insight into NH₃ chemistry on Ir model surfaces has significant technological potential, such as reduce operational costs and improve selectivity for the Ostwald process. Thereby, our findings could support the rational design of next-generation, cost-effective catalysts with lower precious metal content. In the Ostwald process, NH₃ forms nitric oxide (NO) via the ammonia oxidation reaction (AOR). Afterward, NO is converted into nitric acid (HNO₃), a key chemical in fertilizer production. Partial oxidation of NH₃ to nitrogen (N₂) and nitrous oxide (N₂O) can occur, which is undesirable as neither can be further processed into HNO₃. Therefore, a better understanding of the AOR selectivity could significantly enhance the efficiency of the industrially relevant Ostwald process. The AOR takes place under pressures of several bars in industry to increase the formation of NO. However, surface-sensitive studies at these pressures are challenging, and experiments are often carried out at pressures close to 10⁻⁹ bar. We aim to bridge this pressure gap using state-of-the-art instrumentation at PETRA III to evaluate how surface structure influences AOR activity and selectivity under industrially relevant conditions. To study the AOR with high atomic-level detail, we will perform separate photoemission and surface diffraction experiments under operando conditions (different O₂ + NH₃ mixtures in the 0.1 - 0.5 bar pressure range) using different Ir model surfaces. This will allow us to determine structure-activity relationships, having an immediate scientific impact on the field of Ir-based surface catalysis, and potentially helping in the knowledge-driven design of greener catalysts.

• DFG Programme: Research Grants