Surface engineering of nanotubular ferric oxyhydroxide "goethite" on platinum anodes for durable formic acid fuel cells.

A peerless inexpensive electrochemical engineering of spherical Pt nanoparticles (nano-Pt: ca. 100 nm in average diameter) was achieved with intersected ferric oxyhydroxide nanotubes (α-FeOOH (goethite): ca. 20 nm in average diameter). The FeOOH@Pt catalyst exhibited ca. 2.5 and 1.94-times increases in the catalytic activity and poisoning tolerance, respectively, of the formic acid electro−oxidation (FAO) – the anodic reaction in the direct formic acid fuel cells (DFAFCs). Surprisingly, with a post-activation of the FeOOH@Pt catalyst at 0.48 V vs. reversible hydrogen electrode (RHE) in 0.2 mol L−1 NaOH, a favorable Fe2+/Fe3+ transformation succeeded to eliminate the permanent CO poisoning of Pt that impaired the catalytic performance of DFAFCs. This was synchronized (relatively to nano-Pt) with a four-fold increase in the catalytic efficiency, ca. −174 mV shift in the onset potential, and eightfold enhancement in the catalyst's durability for FAO. The activated FeOOH@Pt catalyst also showed a mass activity of 296 mA mg−1 Pt (at 0.8 V), which was ca. nine times higher than that (34 mA mg−1 Pt) of the commercial Pt/C catalyst. The ascertained improvement in the electron transfer at the FeOOH@Pt surface foresees quick industrialization for DFAFCs. TOC. A simple layer-by-layer electrochemical assembly and a post-activation of a peerless inexpensive FeOOH/Pt/GC nanostructured catalyst was recommended for "mitigated CO-poisoning" formic acid electro−oxidation. [Display omitted] • An efficient and robust FeOOH/Pt anodic catalyst was developed for the direct formic acid fuel cells (DFAFCs). • The catalyst's activation at 0.48 V vs. RHE in NaOH resulted in a boosted (fourfold) catalytic performance. • The activation enriched the catalyst surface with α-FeOOH (goethite phase). • The electronic properties of Pt were tuned to accelerate the charge transfer of FAO. • The peerless inexpensive modification of Pt with FeOOH will sustain the market to realize DFAFCs. [ABSTRACT FROM AUTHOR]