P-block elements adsorption induced shift of potential of zero free charge of Pt(111)/HClO4 interface

Potential of zero free charge (PZFCs) of Pt(111)/0.1 M HClO 4 interface with adsorbed P-block elements X ad ( X = I, Br, Te, Se and S) of various coverages are investigated using electrochemical reduction of peroxodisulfate (PDS) as the probe reaction, aiming at understanding the mechanism of adatom in regulating the PZFCs of Pt(111)@X ad /0.1 M HClO 4 interface. Experimental observations reveal that increase adatom coverage on Pt(111) results in a monotonic positive shift in the PZFCs with S, Se and Br adatoms. The maximum PZFCs with saturated S ad , Se ad and Br ad are in the range of ca. 0.5–0.53 V RHE , which is positively shifted by ca. 0.14–0.17 V comparing to the PZFC of unmodified Pt(111)/0.1 M HClO 4 interface. In contrast, whereas I and Te adatoms lead to a nonmonotonic change of PZFCs with coverage, characterized by an initial positive shift up to ca. 0.51/0.48 V RHE followed by a sharp drop down to ca. 0.17/0.14 V RHE at higher coverages. The origin for such phenomenon can be well rationalized by the displacement of adsorbed water on Pt(111) by X ad , such displacement induced change of electron spillover from the Pt surface as well as the electronic effect of X ad and Pt.