Correlating surface structure and electrochemical properties of polycrystalline platinum electrodes

Platinum electrodes are of key importance in electrocatalysis due to their high activity for the hydrogen evolution and oxygen reduction reactions. Industrially-relevant Pt electrodes typically exhibit significant surface heterogeneity ( i.e. , poly-/nanocrystallinity), complicating the establishment of clear relationships between structure and electrochemical properties. To unravel the influence of surface structure on interfacial properties at a fundamental level, two key electrochemical parameters are studied here: the potential of zero total charge ( E pztc ) and the “double-layer” capacity ( C dl ). Using a combination of cyclic voltammetry, electrochemical impedance spectroscopy, and ex situ electron backscatter diffraction, the electrochemical responses of three different polycrystalline Pt electrodes are compared and correlated with their respective facet orientation distributions. We show that, despite significant surface complexity, the E pztc and C dl remain highly sensitive to local facet orientations, mirroring trends previously observed for model stepped single-crystal Pt surfaces. In particular, (100)-type sites dominate the capacitance response in the so-called “double-layer” region (between 0.40 – 0.60 V RHE ), due to pseudocapacitive contributions resulting from a potential-dependent OH ads coverage. These findings confirm that the structure-sensitivity of electrochemical properties previously identified for model systems can be predictably extended to polycrystalline Pt electrodes and provides a fundamental insight into macroscopic electrochemical behavior based on microscopic surface features.