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Structural Transformation of Monocrystalline Platinum Electrodes upon Electro-oxidation and Electro-dissolution

Structural Transformation of Monocrystalline Platinum Electrodes upon Electro-oxidation and Electro-dissolutionAtomic-level understanding of the degradation of Pt materials is important for the rational design of nanoscopic Pt electrocatalysts for fuel cells. We report on the dissolution and structural transformation of spherical, monocrystalline, polyoriented Pt (Pt(spherical)) in 0.50 M aqueous H2SO4 upon potential cycling in the surface oxide formation–reduction region. The potential cycling is performed in the ELEU range (EL = 0.07 V and 0.90 ≤ EU ≤ 1.50 V) to correlate dissolution and morphology data to EU. The amount of dissolved Pt is monitored using flow injection coupled to inductively coupled plasma mass spectrometry (ICPMS), and structural changes, which modify cyclic voltammetry profiles, are examined using scanning electron microscopy (SEM). In the case of EU ≤ 1.20 V, there is minor dissolution of the (100) and (110) facets, while the (111) facet remains stable. In the case of EU ≥ 1.30 V, all facets undergo significant dissolution. Changes in the surface morphology of Pt(spherical) upon repetitive potential cycling in the 0.07–1.50 V range were examined in relation to the number of transients (1 ≤ n ≤ 30000). The SEM images reveal that the (111) facet develops pits, the (100) facet uniformly distributed hillocks (pyramids), and the (110) facet columns. We report structural changes for 25 basal, stepped, and kinked facets. Their analysis demonstrates that the (531) facet is the least roughened and thus the most stable. The original results reported in this article represent a major contribution to the current understanding of the interfacial electrochemistry and electrocatalysis of Pt materials. (Read More)