Impact of Hydrogen Peroxide on Carbon Corrosion in Aqueous KOH Solution (Supporting Information)

Impact of hydrogen peroxide on carbon corrosion is investigated by immersion tests of catalyst-deposited highly oriented pyrolytic graphite (HOPG) samples to an aqueous solution of 1.0 mol dm⁻³ KOH + 5 mmol dm⁻³ H₂O₂. The surfaces of the HOPG samples are observed with field-emission scanning electron microscopy and X-ray photoelectron spectroscopy. HOPG without catalyst shows almost no morphological change while the distribution of C-O and C=O functional groups increases. In contrast, Pt-loaded HOPG exhibits the formation of scars and COO functional groups, which shows a relatively severe carbon corrosion reaction resulting in CO₃²⁻ formation. Since the Pt-loaded HOPG after the immersion test to 0.5 mol dm⁻³ H₂SO₄ + 5 mmol dm⁻³ H₂O₂ shows much smaller scars, it can be concluded that hydrogen peroxide corrodes Pt-loaded carbon more severely in the alkaline electrolyte solution than the acid electrolyte solution. Ag-loaded HOPG also shows the scars, while the sizes of scars are much smaller than those on the Pt-loaded HOPG. In contrast, MnO_x and CoO_x-loaded HOPGs exhibit no scar and minor oxygen-containing functional groups than the HOPG without catalyst, whereas MnO_x and CoO_x-loaded HOPGs shows larger scars than Pt and Ag-loaded HOPGs after electrochemical carbon corrosion test.