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 (Ed = −0.10 V vs RHE, [HCl] = 10 mM and [Na2PtCl6•6H2O] = 0.5 mM) and by varying the deposition charge. For comparison, polycrystalline Pt thin films were prepared using the same solution but with Ed = +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 μA cmPt−2) for the oxidation of ammonia and formic acid, respectively.This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Research Chair program. Also, one of us (EB) would like to acknowledge the financial support of NSERC through an Alexander Graham Bell Canada Graduate Scholarship (CGS) (Master degree) and the Michael Smith Foreign Study Supplements program, as well as the Fond Québécois de la Recherche sur la Nature et les Technologies (FQRNT) through the master research scholarships (B1) program