Platinum-group elements are essential in heterogeneous catalysis for emission control applications due to their exceptional activity. However, their scarcity necessitates strategies to optimize metal utilization and enhance catalyst stability. Alloying platinum with base metals has been shown to improve catalytic activity and noble metal efficiency. Another approach to enhancing catalyst performance and stability is by modifying surface properties with metal oxides or other functional materials. Atomic layer deposition (ALD) enables high control over catalyst composition, structure, and surface properties with Angstrom-level precision, making it a powerful tool for catalyst design and optimization. Previously, it was shown that manganese oxide (MnOx) deposited on Pt/Al2O3 via atomic layer deposition (ALD) improved catalyst durability and promoted CO oxidation rates by supplying oxygen to the Pt during the CO oxidation reaction. In this work, we investigate the influence of MnOx ALD on PtCu/Al2O3 catalysts, using propene as a probe reaction due to its abundance among emitted hydrocarbons. We find that despite having higher overall activity compared to Pt/Al2O3, PtCu/Al2O3 suffers from deactivation, losing up to 50% of its initial activity. Kinetics measurements reveal that ~1 nm of MnOx overlayer can stabilize PtCu against deactivation, while thicker MnOx layers further enhance both the stability and activity of the catalyst for over 24 hours on stream. However, after H2 pretreatment, the MnOx-modified catalysts lose their initial stability and activity, indicating that the oxidized MnOx plays a key role in stabilizing PtCu and facilitating oxygen activation. This study highlights how ALD can be leveraged for mechanistic studies of complex catalyst systems.
