In situ dynamic tracking of heterogeneous nanocatalytic processes by shell-isolated nanoparticle-enhanced Raman spectroscopy

Abstract

Surface molecular information acquired in situ from a catalytic process can greatly promote the rational design of highly efficient catalysts by revealing structure-activity relationships and reaction mechanisms. Raman spectroscopy can provide this rich structural information, but normal Raman is not sensitive enough to detect trace active species adsorbed on the surface of catalysts. Here we develop a general method for in situ monitoring of heterogeneous catalytic processes through shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) satellite nanocomposites (Au-core silica-shell nanocatalyst-satellite structures), which are stable and have extremely high surface Raman sensitivity. By combining operando SHINERS with density functional theory calculations, we identify the working mechanisms for CO oxidation over PtFe and Pd nanocatalysts, which are typical low- and high-temperature catalysts, respectively. Active species, such as surface oxides, superoxide/peroxide species and Pd–C/Pt–C bonds are directly observed during the reactions. We demonstrate that in situ SHINERS can provide a deep understanding of the fundamental concepts of catalysis.

Practical Guidelines for Shell‐Isolated Nanoparticle‐Enhanced Raman Spectroscopy of Heterogeneous Catalysts

“…The remaining Raman bands are associated with Si−OH (990 cm −1 ) and Si (520 cm −1 ) from the Si wafer . However, in contrast to other work, we observed the growth of carbon during the reduction. The major contribution to the SHINER spectra consists of carbonaceous species as is apparent by the carbon D and G bands at respectively 1350 and 1590 cm −1 (Figure b).…”

Thermally Stable TiO2‐ and SiO2‐Shell‐Isolated Au Nanoparticles for In Situ Plasmon‐Enhanced Raman Spectroscopy of Hydrogenation Catalysts

“…[26] An importants tep forward in the development of SHINERS in catalysis was recently realized by Tian et al by demonstrating SHINs as au niversal support materiala nd nano-antenna for various solid catalyst nanoparticles. [27] In a follow-up study,t hey provedt hat with SHINERS, the typeo f coating material hasa ne vident effect on the behavior of solid catalysts. [28] In this research work, we present ar elativelyf acile colloidal method to prepare metal@TiO 2 @Au and metal@SiO 2 @Au shellisolated nanoparticles (SHINs) and illustrate their potential in the field of heterogeneous catalysis ( Figure 1).…”

“…An important step forward in the development of SHINERS in catalysis was recently realized by Tian et al. by demonstrating SHINs as a universal support material and nano‐antenna for various solid catalyst nanoparticles . In a follow‐up study, they proved that with SHINERS, the type of coating material has an evident effect on the behavior of solid catalysts…”

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

“…[28] As shown in Figure 5d,t he Pt-Pd overlayers show the best performance for FOR (the comparison to 1MLP ta nd 1MLP do n1ML Pt covered Au(111) are displayed in Figure S6), giving a6.8-and 1.1-times increase in oxidation current densities compared to Pt(111) and 1MLPd, respectively.S imilarly,b etter CO oxidation activity is also observed in Figure 5e.S imilar improved performance of Ag@Pd overlayers toward formic acid decomposition were ascribed to optimal structural and electronic effects. [29] Herein, in situ spectra display the Pd-C frequencyi sr ed shifted on Pt-Pd overlayers compared to 1MLPdasshown in Figure 5f.Whenthe potential increased, the Pt-O and Pd-O bands at about 562 cm À1 and 650 cm À1 ,r espectively,t hat are also observed on Pd nanocatalysts, [30] appear after 0.3 Vo n the Pd-Pt layer, while it appears after 0.7 Von1ML Pd. From this detailed fingerprint information on the metal-molecule interactions,i tc an be concluded the weaker surface interaction with CO,t he adsorption of reactive oxygen, and synergistic effects contribute to the higher catalytic activity.…”