Efficient Direct Formic Acid Fuel Cells (DFAFCs) Anode Derived from Seafood waste: Migration Mechanism

Abstract

Commercial Pt/C anodes of direct formic acid fuel cells (DFAFCs) get rapidly poisoned by in-situ generated CO intermediates from formic acid non-faradaic dissociation. We succeeded in increasing the Pt nanoparticles (PtNPs) stability and activity for formic acid oxidation (DFAFCs anodic reaction) by embedding them inside a chitosan matrix obtained from seafood wastes. Atop the commercial Pt/C, formic acid (FA) is predominantly oxidized via the undesired poisoning dehydration pathway (14 times higher than the desired dehydrogenation route), wherein FA is non-faradaically dissociated to CO resulting in deactivation of the majority of the Pt active-surface sites. Surprisingly, PtNPs chemical insertion inside a chitosan matrix enhanced their efficiency for FA oxidation significantly, as demonstrated by their 27 times higher stability along with ~400 mV negative shift of the FA oxidation onset potential together with 270 times higher CO poisoning-tolerance compared to that of the commercial Pt/C. These substantial performance enhancements are believed to originate from the interaction of chitosan functionalities (e.g., NH2 and OH) with both PtNPs and FA molecules improving FA adsorption and preventing the PtNPs aggregation, besides providing the required oxygen helping with the oxidative removal of the adsorbed poisoning CO-like species at low potentials. Additionally, chitosan induced the retrieval of the Pt surface-active sites by capturing the in-situ formed poisoning CO intermediates via a so-called “migration mechanism”.