Microelectrochemical Study on the Surface Oxidation of Pt: The Effects of Crystal Orientation and Grain Boundary

Abstract

Microelectrochemical polarization measurements of polycrystalline Pt were performed to clarify the effect of the crystal orientation and grain boundary on the surface oxidation of Pt. Cyclic voltammograms (CV) for Pt(100)-like and Pt(110)-like grains on polycrystalline Pt after mechanical polishing showed no anodic peak below 1.35 V, which is similar to that for well-annealed Pt(111) single crystal. The anodic current of Pt(110)-like grain was significantly larger than Pt(100)-like. A small but concrete current increase appeared around 1.051.3 V in the CV of the surface including grain boundaries. This suggests the grain boundary may be the preferential site for the dissolution.

Dissolution of Platinum Single Crystals in Acidic Medium

“…The surface of Pt(poly) is made up of the Pt basal planes, higher index facets and includes many grain boundaries. Grain boundaries can act as preferential sites for oxidation and dissolution . Therefore, it is difficult to predict the quantity of dissolution and onset potential relative to Pt(111), Pt(100) and Pt(110).…”

“…Grain boundaries can act as preferential sites for oxidation and dissolution. [59] Therefore, it is difficult to predict the quantity of dissolution and onset potential relative to Pt(111), Pt(100) and Pt(110). However, it is reasonable to assume that Pt(poly) would have a behaviour in between the basal planes.…”

Revisit to Grain Boundary Effect in Pt Nanocrystals toward the Oxygen Electroreduction Reaction

“…Furthermore, studies have revealed that GBs can act as preferential sites for oxidation, and the exposed crystallographic facet of an electrocatalyst controls the oxidation state of the atoms. [40,41] In bimetallic Pt alloys, an optimal CN of ~8 is assumed to be present in GBs before electrochemical treatments. However, [36] Copyright 2016, John Wiley & Sons.…”

“…Therefore, the ORR performance may decrease on GB sites. Furthermore, studies have revealed that GBs can act as preferential sites for oxidation, and the exposed crystallographic facet of an electrocatalyst controls the oxidation state of the atoms [40,41] …”