Enhanced formic acid oxidation on polycrystalline platinum modified by spontaneous deposition of gold. Fourier transform infrared spectroscopy studies

PAULA S. CAPPELLARI; GONZALO GARCÍA; JONATHAN FLORÉZ-MONTAÑO; CESAR A. BARBERO; ELENA PASTOR; GABRIEL A. PLANES

JOURNAL OF POWER SOURCES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 296 p. 290 - 297

0378-7753

Formic acid and adsorbed carbon monoxide electrooxidation on polycrystalline Pt and Au-modified Pt surfaces were studied by cyclic voltammetry (CV), lineal sweep voltammetry (LSV) and in-situ Fourier transform infrared spectroscopy (FTIRS) techniques. With this purpose, a polycrystalline Pt electrode was modified by spontaneous (electroless) deposition of gold atoms, achieving a gold surface coverage (θ) in the range of 0 ≤ θ ≤ 0.47. Results indicate the existence of two main pathways during the formic acid oxidation reaction, i.e. dehydration and dehydrogenation routes. At higher potentials than 0.5 V the dehydrogenation pathway appears to be the operative at both Pt and Au electrodes. Meanwhile, the dehydration reaction is the main pathway for Pt at lower potentials than 0.5 V. It was found that reaction routes are easily tuned by preferential Au deposition on Pt sites with (110) and (100) orientations. These Pt open surface sites are the responsible for the formic acid dehydration reaction and hence for the catalytic formation of adsorbed carbon monoxide (COad). Gold deposition on these Pt open sites produces an enhanced activity toward the HCOOH oxidation reaction. This result is discussed in terms of surface structure, nature of the material and kinetic of the reaction. In general terms, the surface inhibition of the reaction by adsorbed intermediates (indirect pathway) is almost absent at gold-modified Pt electrodes, and therefore the direct pathway appears as the main route during the formic acid electrooxidation reaction.