Arabian Journal of Chemistry (Mar 2023)

Amendment of palladium nanocubes with iron oxide nanowires for boosted formic acid electro−oxidation

  • Heba H. Farrag,
  • Islam M. Al-Akraa,
  • Nageh K. Allam,
  • Ahmad M. Mohammad

Journal volume & issue
Vol. 16, no. 3
p. 104524

Abstract

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To quickly move the formic acid (FA) fuel cells closer to a real commercialization, an inexpensive, efficient, and durable electrocatalyst for the direct FA electro-oxidation (FAEO) was developed. This involved a sequential modification of a glassy carbon (GC) substrate with palladium nanocubes (ca. 70 nm, nano-Pd) and iron oxide nanowires (nano-FeOx, ca. 40 nm and 150 nm in average diameter and length, respectively). The deposition sequence and loading level of nano-FeOx in the catalyst were optimized to minimize the catalyst's poisoning with CO that might probably release from a parallel dehydration of FA or from CO2 reduction. Surprisingly, the FeOx/Pd/GC catalyst exhibited a high (21.6 mA cm−2) specific activity for FAEO, which denoted ca. 7 times that of the “pristine” Pd/GC catalyst. This was synchronized with a better (up to fivefold increase in turnover frequency) “long-termed” stability that extended for 90 min of continuous electrolysis at room temperature. A successful effort was dedicated to improving more the catalyst's stability by activating the catalyst electrochemically at –0.5 V vs Ag/AgCl/KCl (sat.) in 0.2 mol L−1 NaOH. The CO stripping agreed perfectly with the impedance analysis in appending the observed enhancement in the catalytic efficiency of FAEO to a favorable electronic modulation at the Pd surface that boosted the oxidative desorption of poisoning CO species at a lower potential.

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