Optimization and DFT study for boosted electooxidation of formic acid at NiOx modified Pt using urea derivatives as...

This paper addresses the enhancement of formic acid electrooxidation (FAO) at Pt and Pt-NiOx nanoparticles based-catalysts assisted with urea derivatives as blending fuels. Blending formic acid with various ratios of urea derivatives showed noticeable enhancements of FAO as demonstrated by a favorable negative shift of its onset potential (E_onset) and increase of its peak current density concurrently with suppression of the amount of CO poisoning reaction intermediate. Among all the used derivatives, phenyl urea (PU) showed superior enhancing effect towards the direct FAO with a minimal CO formation together with a favorable negative shift of E_onset by 150 mV. The superb enhancing effect of PU over U and/or other urea derivatives (investigated herein) is attributed mainly to the withdrawing inductive effect of the phenyl group attached to urea. That is the formation of 8 membered ring via hydrogen bonding between PU and formate anion is thought to enrich the electrode/electrolyte interface by FA in such a favorable orientation facilitating the C-H scissoring resulting in the direct oxidation of FA (to CO₂) with almost no possibility for CO formation. DFT calculations are used to support this assumption in line with experimental results.