Formic acid electrooxidation activity of Pt and Pt/Au catalysts: Effects of surface physical properties and irreversible adsorption of Bi

Abstract

Revealing formic acid oxidation (FAO) behaviors and designing a catalyst are very important in direct formic acid fuel cell industry. Herein, we introduced various Pt substrates of Pt nanoparticles (Pt NPs), Pt deposits on Au nanoparticles (Pt/Au NPs), Pt disk, and Pt deposits on bulk Au disks (Pt/Au disk), and the catalysts modified with Bi by irreversible adsorption. For FAO in the absence of Bi-modification, the catalytic activity increased in the order of Pt disk < Pt NP < Pt/Au disk < Pt/Au NP. On the other hand, the presence of Bi on Pt surfaces enhanced the catalytic performance in the order of Pt/Au NP < Pt/Au disk approximate to Pt NP < Pt disk. The observed activities were found to be highly correlated with a synergistic effect by Bi modification and the surface physical properties of various modified Pt substrates. The single fuel cell performances of various Bi-modified Pt NPs and Pt/Au NPs were additionally examined for real application: the performances per substrate surface area, and Pt mass of Pt/Au NPs and Bi/Pt/Au NPs were better than those of Pt NP and Bi/Pt NPs. Furthermore, the presence of Bi corresponded to single cell potentials higher than those in the absence of Bi by more than 0.1 V at 100mA cm(-2). The full understanding of the effects of surface physical properties and the irreversible adsorption of Bi further deepens the catalytic pathways of formic acid oxidation. (C) 2018 Elsevier Ltd. All rights reserved.