SERS for Probing Highly Reactive Pd Sites with Elongated Pd-Pd Bonds on the Au Surface

Bondlength is an important structural parameter that can affectthe activity of catalysts. In core-shell gold-palladium(Au@Pd) nanocatalysts, sites with elongated Pd-Pd bonds arisingfrom lattice mismatches between Au and Pd exhibit distinct catalyticactivity. Despite their impact on catalysis, bond-length alternationshave not been directly observed or characterized. Herein, we usedthe surface-enhanced Raman scattering (SERS) spectra of chemisorbed2,6-dimethylphenyl isocyanide (2,6-DMPI) structural reporter to spectroscopicallyprobe elongated Pd-Pd bonds on Au@Pd. In a catalyzed Suzuki-Miyauracoupling reaction, we found that strained sites with elongated Pdbonds are >100 times more active than unstrained sites. SERS spectraand theoretical simulations reveal that changes in bond lengths influencethe electronic state of Pd atoms more profoundly than substitutingcoordination atoms or reducing coordination numbers. Further, we discoveredthat Pd growth begins as a continuous atomic chain rather than a singleatom as thought previously.

Automated summary

Bond length is an important structural parameter that can affect the activity of catalysts. In core-shell gold-palladium (Au@Pd) nanocatalysts, elongated Pd-Pd bonds resulting from lattice mismatches between Au and Pd are found to exhibit distinct catalytic activity. Surface-enhanced Raman scattering (SERS) spectra of chemisorbed 2,6-dimethylphenyl isocyanide (2,6-DMPI) were used to investigate the elongated Pd-Pd bonds on Au@Pd. The study revealed that strained sites with elongated Pd bonds are more than 100 times more active in a catalyzed Suzuki-Miyaura coupling reaction.