Understanding the molecular mechanism of oxygen reduction reaction using in-situ Raman spectroscopy

Polymer electrolyte membrane fuel cells (PEMFCs) offer a clean and efficient energy conversion solution, but the cathodic oxygen reduction reaction (ORR) presents significant challenges to the further advancement of PEMFCs due to its slow kinetics. Understanding the fundamental reaction mechanism of ORR is crucial for designing efficient ORR electrocatalysts. This review focuses on in-situ surface-enhanced Raman spectroscopy (SERS) study of ORR on various Pt-based catalysts, from model single-crystal electrodes to efficient nanocatalysts. By capturing key intermediate species, SERS provides valuable insights into the ORR mechanism. Various intermediate species, including adsorbed oxygen (O∗), hydroxyl (OH∗), peroxide (OOH∗), etc., have been in-situ detected and correlated with the electrochemical performance. Such information not only helps to unveil the specific reaction pathway but also provides valuable guidance for the synthesis of efficient ORR catalysts towards PEMFCs.