Probing Interfacial Electronic and Catalytic Properties on Well‐Defined Surfaces by Using In Situ Raman Spectroscopy

Heterogeneous metal interfaces play a key role in determining the mechanism and performance of catalysts. However, in situ characterization of such interfaces at the molecular level is challenging. Herein, two model interfaces, Pd and Pt overlayers on Au single crystals, were constructed. The electronic structures of these interfaces as well as effects of crystallographic orientation on them were analyzed by shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) using phenyl isocyanide (PIC) as a probe molecule. A clear red shift in the frequency of the C≡N stretch (νNC) was observed, which is consistent with X‐ray photoelectron spectroscopy (XPS) data and indicates that the ultrathin Pt and Pd layers donate their free electrons to the Au substrates. Furthermore, in situ electrochemical SHINERS studies showed that the electronic effects weaken Pt−C/Pd−C bonds, leading to improved surface activity towards CO electrooxidation. Shell seekers: Shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) was used to probe the electronic structures and reveal the catalytic mechanisms on Pd/Pt‐overlayer‐coated Au single crystals. This work opens up a novel way to detect the electronic structures of heterogeneous metal interfaces and understand catalytic mechanisms at the molecular level.