Perchloric acid solution

Silver nitrate (AgNO₃, ACS reagent, ≥99.0%), palladium(II) acetylacetonate (Pd(acac)₂, 99%), gold(III) chloride trihydrate (HAuCl₄·3H₂O, ACS reagent, ≥49.0% Au basis), oleylamine (70%, technical grade) and Nafion 117 solution (5% in a mixture of lower aliphatic alcohols and water) were purchased from Sigma-Aldrich. Ethanol (>99.7%), mEthanol (>99%), toluene (>99.5%) and perchloric acid solution (70%) were purchased from Beijing Chemical Works. Vulcan XC-72 carbon powders (XC-72C with BET surface area of 250 m² g⁻¹ and average particle size of 40 ∼ 50 nm) were purchased from Cabot. Commercial Pd/C catalyst was purchased from Johnson Matthey (JM). All chemicals were used as received. Deionized water was distilled by a Milli-Q Ultrapure-water purification system. All glassware and Teflon-coated magnetic stirring bars were cleaned with aqua regia, followed by copious rinsing with deionized water before drying in an oven.

Silver nitrate (AgNO₃, ACS reagent, ≥99.0%), palladium(II) acetylacetonate (Pd(acac)₂, 99%), platinum(II) acetylacetonate (Pt(acac)₂, 97%), gold(III) chloride trihydrate (HAuCl₄·3H₂O, ACS reagent, ≥49.0% Au basis), oleylamine (70%, technical grade) and Nafion 117 solution (5% in a mixture of lower aliphatic alcohols and water) were purchased from Sigma-Aldrich. Ethanol (>99.7%), mEthanol (>99%), toluene (>99.5%) and perchloric acid solution (70%) were purchased from Beijing Chemical Works. Vulcan XC-72 carbon powders (XC-72C with BET surface area of 250 m² g⁻¹ and average particle size of ca. 40–50 nm) were purchased from Cabot. All chemicals were used as received.

Silver nitrate (AgNO₃, ACS reagent, ≥99.0%), platinum(II) acetylacetonate (Pt(acac)₂, 97%), palladium(II) acetylacetonate (Pd(acac)₂, 99%), oleylamine (70%, technical grade) and Nafion 117 solution (5% in a mixture of lower aliphatic alcohols and water) were purchased from Sigma-Aldrich. Ethanol (>99.7%), mEthanol (>99%), toluene (>99.5%), perchloric acid solution (70%), sodium chloride (NaCl, analytical grade) and acetic acid (C₂H₄O₂, analytical grade) were purchased from Beijing Chemical Works. Vulcan XC-72 carbon powders (XC-72C with BET surface area of 250 m² g⁻¹ and average particle size of 40 ∼ 50 nm) were purchased from Cabot. All chemicals were used as received. Deionized water was distilled by a Milli-Q Ultrapure-water purification system. All glassware and Teflon-coated magnetic stirring bars were cleaned with aqua regia, followed by copious rinsing with deionized water before drying in an oven.