Effect of the nature of (100) surface sites on the electroactivity of macroscopic Pt electrodes for the electrooxidation of ammonia

The electrocatalytic activity of preferentially oriented (100) Pt electrodes for the electro-oxidation of ammonia was assessed as a function of the deposition potential, E-d. It is shown that under the applied electrodeposition conditions, polycrystalline Pt is formed at E-d = +0.10 V vs RUE, while preferentially oriented {100} Pt electrodes with ca. 40% of (100) surface sites are formed at E-d = 0.00 V and -0.10 V vs RHE. However, at E-d = 0.00 V. similar to 40% of these sites are long (100) terraces, while this proportion is only similar to 25% at E-d = -0.10 V. the remaining being (100) step sites. Cyclic voltammetric (0.2 M NaOH + 0.1 M NH3) and chronoamperometric (at +0.60 V vs RHE) measurements were performed to assess the electrocatalytic properties of the Pt films. The occurrence of Pt (100) surface sites leads to a factor of 5-6 increase of the current (expressed as mu A cm(Pt)(-2)) for the oxidation of ammonia as compared to polycrystalline Pt. (C) 2012 Elsevier B.V. All rights reserved.