Hierarchically structured iron-doped silver (Ag–Fe) lotus flowers for an efficient oxygen reduction reaction

Abstract

The development of cheap and efficient electrocatalysts for the oxygen reduction reaction (ORR) is vital for the immediate commercialization of fuel cells which are still limited by the high cost and low performance of the utilized commercial Pt-based electrodes. As a promising alternative, this study reports on the synthesis of hierarchical iron-doped silver lotus flowers (AgFe_lotus) by a facile chemical procedure as robust and efficient ORR electrocatalysts. Succinic acid was used as a structure directing agent to tune the morphology of undoped and iron-doped silver particles. In the absence of succinic acid, ball-like silver particles were obtained, while using 2 mM succinic acid led to peony-like flower structures. The doping of silver peony-flowers with iron resulted in lotus-like flower structures with high electrocatalytic activity for ORR together with outstanding tolerance against poisoning with various hydrocarbon (HC) impurities, in situ generated during fuel cell operation, as well as different fuels from anodic crossover. AgFe_lotus exhibited a superior ORR activity with more than 40 times higher stability than the commercial Pt/C catalyst in alkaline media. This substantial performance enhancement is attributed to the unique lotus-like flower structures providing more electroactive surface sites, in addition to the iron dopants which facilitate ORR charge transfer.