Understanding the Effect of the Adatoms in the Formic Acid Oxidation Mechanism on Pt(111) Electrodes

Abstract

The engineered search for new catalysts requires a deep knowledge about reaction mechanisms. Here, supported by a combination of computational and experimental results, the oxidation mechanism of formic acid on Pt(111) electrodes modified by adatoms of the pblock is elucidated for the first time. DFT calculations reveal that some adatoms, such as Bi or Pb, have positive partial charge when adsorbed on the bare surface whereas others, Se or S, remain virtually neutral. When the partial charge is correlated with previously reported experimental results for the formic acid oxidation reaction, it is found that the partial positive charge is directly related to the increase in catalytic activity of the modified surface. Further, it is obtained that such a positive partial charge is directly proportional to the electronegativity difference between the adatom and Pt. Thus, the electronegativity difference can be used as an effective descriptor for the expected electrocatalytic activity. Furthermore, this partial positive

Supportless, Bismuth-Modified Palladium Nanotubes with Improved Activity and Stability for Formic Acid Oxidation

“…6,[12][13][14][15][16][17][18] The addition of adatoms to the catalyst surface, like Bi or Sb, has been shown to improve formic acid electro-oxidation activity at low overpotentials by so-called ensemble or third-body effects. 4,5,[19][20][21][22][23][24][25] Coupled in situ surface-enhanced infrared spectroscopy and first-principles density functional theory (DFT) calculations indicate that the addition of adatoms can influence the configuration of the formic acid molecule at the catalyst surface. 4 High adatom coverage can promote the adsorption of formic acid in the CH-down configuration 4 that is considered the precursor for the direct formic acid oxidation (FAO) pathway and high activity at low overpotentials.…”

Heterogeneous electrocatalysis of formic acid oxidation on platinum single crystal electrodes

“…Additionally, temperature dependent studies revealed that the activation energy for the reaction diminished as the coverage increases [26,27]. Moreover, the values were around 20 kJ mol -1 for the Bi coverage that displays the higher activity.…”

“…This behavior suggests that reaction requires free platinum sites, and that the enhancement takes place on those free sites close neighborhood to sites occupied by the adatom. It was also realized that the enhancement of the activity was dependent on the electronegativity of the adatom: better results were obtained with the less electronegative adatoms [21,26].…”

PtAu catalyst with enhanced activity for formic acid oxidation

“…It turned out that HCl is a promising capping and stabilizing agent for obtaining nanocatalysts with characteristics of single crystals and preferential surface facet orientation [17,18]. It is well known that formic acid electro-oxidation at lower potentials is almost inhibited on Pt(100) and Pt(110) surfaces of single crystals.…”