In situ exploration of oxygen electrocatalysis using core-shell nanostructure-enhanced Raman spectroscopy

Abstract

Advancements in fuel cells and water electrolyzers have significantly bolstered the utilization of hydrogen energy. Notably, the oxidation and reduction processes of oxygen at the electrode—termed oxygen evolution reaction (OER) and oxygen reduction reaction (ORR)—manifest sluggish reaction kinetics, thus requiring noble metals as catalysts, which considerably impedes system efficiency and cost. The imperative for enhancing reaction rates and diminishing overpotential necessitates the development of effective catalysts, which strongly depends on the mechanistic understanding of these reactions at the molecular level. Therefore, this review summarizes our recent efforts in utilizing in situ enhanced Raman spectroscopy, especially the borrowing surface-enhanced Raman spectroscopy (SERS) strategy, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), and the SHINERS-satellite strategy, to capture oxygen intermediate species as a bridge to investigate the molecular mechanisms of OER and ORR. Combining in situ SERS with other characterization techniques and theoretical simulation, the structural evolution of active sites and intermediates, including ∗OOH, ∗OH, ∗OO, etc., during OER/ORR has been monitored under reaction conditions, and the reaction mechanisms together with structure-activity correlations have been identified at the molecular level. These findings may provide a pivotal scientific foundation towards the discovery of better materials for electrochemical hydrogen energy.