Atomically Dispersed Platinum on Gold Nano-Octahedra with High Catalytic Activity on Formic Acid Oxidation

Platinum was epitaxially deposited on gold octahedral nanocrystals using an electrochemical method. The coverage of platinum on the gold surface was finely controlled from fully covered multiple overlayers (5 monolayers; denoted as ML) to atomically dispersed submonolayer (0.05 ML). Catalytic activity for formic acid oxidation increased significantly (0.52 A/mg_Pt for 5 ML to 62.6 A/mg_Pt for 0.05 ML) with decreasing coverage. This high activity resulted from the control of the reaction pathway toward direct oxidation producing no surface-poisoning species, induced by the absence of platinum ensembles and the bifunctional effect from neighboring Pt–Au sites. The distribution of atomically dispersed platinum was further confirmed by no activity for methanol oxidation, which necessitates platinum ensembles. This result exemplifies that a rational design of the catalyst nanostructure can lead to contrasting activities with the same catalyst, unprecedentedly high activity for formic acid oxidation vs no activity for methanol oxidation

Support Effects in Single-Atom Platinum Catalysts for Electrochemical Oxygen Reduction

Single-atom catalysts (SACs) provide an ideal platform for reducing noble-metal usage. SACs also exhibit unusual catalytic properties due to the absence of a metal surface. The role of the support may have a significant effect on the catalytic properties, similar to that of the ligand molecules in homogeneous catalysts. Here, the support effect was demonstrated by preparing a single-atom platinum catalyst on two different supports: titanium carbide (Pt1/TiC) and titanium nitride (Pt1/TiN). The formation of single-atom Pt was confirmed by STEM, EXAFS, and in situ IR spectroscopy. Pt1/TiC showed higher activity, selectivity, and stability for electrochemical H₂O₂ production than Pt1/TiN. Density functional theory calculations presented that oxygen species have strong affinity into Pt1/TiN, possibly acting as surface poisoning species, and Pt1/TiC preserves oxygen–oxygen bonds more with higher selectivity toward H₂O₂ production. This work clearly shows that the support in SACs actively participates in the surface reaction and does not just act as anchoring sites for single atoms