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

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 ≈ 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 100 mA 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.