Sensitivity and Vulnerability of the Pt Surface to Alkaline Solution

Surface (electro)chemistry of platinum (Pt) remains a long-standing yet vibrant topic of interest. pH value of electrolytes has been found to play an important role in affecting various electrochemical behaviors of Pt. This study emphasizes the chemical sensitivity of the Pt surface to alkaline solutions and the resulting vulnerability of its electrochemical activity and stability for hydrogen electrocatalytic oxidation (HOR) on Pt. In situ and ex-situ characterizations reveal that simple bathing in an alkaline solution can profoundly alter the Pt surface characteristics, which exhibit a lower work function and upshifted d-band center compared to both the pristine and acid-bathed samples. Such chemical sensitivity of the Pt surface to alkaline solution might be associated with a rapid and spontaneous neutralization reaction between OH– (acting as a Brønsted base) and preexisting surface PtxO species (acting as Lewis acid) in alkaline conditions. During the HOR process, the preadsorbed OH– decreases the ECSA, imparts a significant energy barrier for oxidative desorption of Had, and impairs the catalytic stability of the Pt electrocatalysts. This work calls for attention to the unignorable adverse sensitivity and vulnerability of Pt electrocatalysts in alkaline media.