Electrodeposited platinum thin films with preferential (100) orientation: Characterization and electrocatalytic properties for ammonia and formic acid oxidation

The electrocatalytic activity of preferentially oriented {100} Pt electrodes for the electro-oxidation of ammonia (0.2 M NaOH + 0.1 M NH3) and formic acid (0.5 M HCOOH + 0.5 M H2SO4) was assessed. They were prepared without using any surfactant through potentiostatic deposition (E-d = -0.10 V vs RHE, [HCl] = 10 mM and [Na2PtCl6 center dot 6H(2)O] = 0.5 mM) and by varying the deposition charge. For comparison, polycrystalline Pt thin films were prepared using the same solution but with E-d = +0.10 V vs RHE. Quantification of the fraction of (111) and (100) sites was performed by bismuth irreversible adsorption and deconvolution of the hydrogen region, respectively. Samples with as much as 47% of (100) surface sites were obtained. The preferential orientation was further confirmed by CO stripping voltammetry that exhibits similar characteristic features, as well as a similar potential of zero total charge than those expected for a preferential (100) surface. As compared to polycrystalline Pt, the occurrence of Pt (100) surface sites leads to an electrocatalytic activity enhancement by a factor of 4.8 and 2.6 (expressed as mu A cm(Pt)(-2)) for the oxidation of ammonia and formic acid, respectively. (C) 2012 Elsevier B.V. All rights reserved.