Existing studies of single crystal surface/polymer interfaces revealed intriguing interfacial behaviors . Nafion is the most widely used proton conducting polymer electrolyte, and its ionomer is frequently used as a binder in electrode preparation . Thus, existing literature focus on the interface between Nafion and different single crystal facets of Pt. In a pioneering work, Attard and coworkers revealed that adsorption of the sulfonate group in Nafion depends sensitively on the width of terrace on single crystal Pt facets with different step densities . The sharp sulfonate adsorption/desorption cyclic voltammetric peaks could serve as diagnostic features for the adsorbed OH at step sites on Pt surfaces. Kodama and coworkers investigated the effect of the structure of the backbone and side-chains of perfluorosulfonic acid ionomers on the sulfonate adsorption on Pt single crystal surfaces and the oxygen reduction reaction (ORR) activity . It was demonstrated that the structure of the polymer backbone and length of the side-chain, which do not specifically adsorb on Pt, have a significant impact on the sulfonate adsorption.