Crystal Structure-mediated Difference in Spectroscopic Behavior of OER Intermediate on MnO2 in the Presence of Pyridine

An in situ spectroelectrochemical technique was applied to MnO2 oxygen evolution electrocatalysts with different crystal structures (α-MnO2 and β-MnO2) to monitor the Mn3+ intermediate in the presence of pyridine. Upon the addition of pyridine to the electrolyte, the UV-vis signal of Mn3+ disappeared on β-MnO2 while remaining on α-MnO2. Electrochemical and spectroscopic analysis confirmed that pyridine accelerated interfacial charge transfer between the electrolyte and the MnO2 surface by coordinating to the MnO6 octahedra, triggering more activity enhancement than α-MnO2.