Highly Dispersed, Platinum Implanted on Nanostructured Manganese Oxide Systems for Oxygen Reduction Reaction

Platinum (Pt) nanoparticle catalysts are important in key chemical processes and the automotive industry. To optimize the efficiency of such catalysts, the most practical way is to increase the exposed surface of platinum by creating small particles to increase the active surface area. Due to this, the most efficient catalyst for the oxygen reduction reaction (ORR) may be a single atom of platinum. Reducing these catalyst nanoparticles to single atoms is highly sought after, though achieving this is quite challenging. However, it is unclear how the motif of a single atom affects the reaction. Here, we bridge the gap between isolated single atoms and their motifs by synthesizing three different manganese oxide supports with isolated Pt atoms using a robust adsorption-based method. Manganese oxide offers Pt stability in such materials. Solid-state nuclear magnetic resonance (SS-NMR), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS) were used to determine the coordination and electronic environments of these catalysts and were compared to the activity to determine the active motifs. These catalysts showed an improvement over the leading commercial Pt/C (10% wt) catalyst by 11%, as determined by cyclic voltammetry. The activity followed the trend Pt-OMS-2 > Pt/C > Pt-K-OL-1 > Pt-Mn3O4. From TEM, XPS, SS-NMR, and electrochemical experiments, we reveal that the single-atom motif of Pt in OMS-2 is the most active for this reaction and that other motifs show little activity.