Au@h-BN Core–Shell Nanostructure as Advanced Shell-Isolated Nanoparticles for In Situ Electrochemical Raman Spectroscopy in Alkaline Environments

Abstract

Recent advancements in in situ electrochemical Raman spectroscopy using shell-isolated nanoparticles have facilitated direct analysis of electrochemical mechanisms. However, shell materials such as SiO₂ and Al₂O₃ commonly adopted for shell-isolated nanoparticle-enhanced Raman spectroscopy are unstable and unreliable in alkaline environments, posing significant obstacles for relevant research in the alkaline environment. While alternative shell materials have been explored, finding suitable replacements for traditional SiO₂ shells is still challenging. To address this issue, this study proposes hexagonal boron nitride (h-BN), with atomically ultrathin and insulating properties, as an alternative shell material. Specifically, pinhole-free Au nanoparticles coated by an h-BN shell (Au@h-BN) with a uniform thickness of 1 nm are synthesized through a controlled two-step process. The resulting Au@h-BN exhibits more pronounced Raman scattering and long-term stability under alkaline conditions compared to Au@SiO₂. Theoretical simulations support a stronger electromagnetic field distribution around Au@h-BN compared to that around Au@SiO₂. In situ Raman studies conducted during electrochemical reactions of Ni and Cu electrodes demonstrate the superior Raman enhancement effect and durability of Au@h-BN compared to Au@SiO₂. These results suggest that Au@h-BN holds significant potential for advancing long-term in situ Raman studies in alkaline systems, supporting the development of efficient catalysts for sustainable energy applications.