Recent advances in Raman spectroelectrochemistry on single-crystal surfaces

Benefiting from a principally contaminant-free and well-defined surface, single-crystal electrodes offer new insights into interfacial processes and are important in electrochemistry. The early impetus for using single-crystal electrodes in electro-catalysis was to investigate the surface structure at the atomic level for the reactions that are sensitive to the surface. These studies were usually performed in an ultra-high vacuum with atomic force microscopy (AFM), scanning tunneling microscope (STM), and X-ray methods to avoid the contamination. However, such characterizations are limited in their ability to identify chemical species definitively, a limitation that has similarly plagued the study of single-crystals. Recent advances in shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) have enabled the detection of reaction intermediates on single-crystal electrodes, in which shell-isolated nanoparticles on the single-crystal electrode can enhance the Raman signal from the surface, without changing the surface structure and electrochemical response. Thus, this work aims to review recent advances in Raman spectroelectrochemical studies on single-crystal electrode surfaces. The discussion focuses on how SHINERS technology has enabled the effective detection of intermediate species and, when combined with the electrochemical method, has yielded novel insights into the dynamic evolution of surface structure and electrocatalytic reaction mechanisms. Finally, the challenges and future of single-crystal electrodes are introduced.