Pt–Rh Model Nanoparticle Catalysts for Selective Oxidation of Ammonia to Nitrogen─A Systematic Screening Study

High Resolution Image Download MS PowerPoint Slide Abatement processes for ammonia (NH 3 ) slip have gained renewed attention due to growing interest in using liquid NH 3 as a marine fuel. A promising approach is selective catalytic oxidation (SCO) of NH 3 to nitrogen (N 2 ). This study presents the catalytic performance of five well-defined Al 2 O 3 -supported mono- and bimetallic Pt–Rh model catalysts for this reaction. Key findings show that the larger Pt nanoparticles (17 nm) exhibit a higher NH 3 turnover frequency (TOF) than the smaller ones (8 nm) while maintaining similar product selectivity. Additionally, the NH 3 TOF decreases in the order Pt > Pt 1– x Rh x solid solution > Rh. Despite this trend, the catalysts Pt, Pt 1– x Rh x solid solution, and Rh exhibit narrow and distinct temperature windows where the N 2 selectivity exceeds 80% at 195–225, 240–250, and 300–315 °C, respectively. Thermal stability tests conducted in air for 8 h and 1 week reveal that both the Rh(core)–Pt(shell) and the Pt 1– x Rh x solid solution nanoparticles undergo Rh surface enrichment. These results indicate that neither elemental configuration remains stable under the SCO-NH 3 conditions.