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 (AgFelotus) 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. AgFelotus 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.

Silver–Iron Hierarchical Microflowers for Highly Efficient H2O2 Nonenzymatic Amperometric Detection

“…As clearly shown in this figure, AgFe amaranth maintains its structure and the morphology after hydrogen peroxide electrolysis. It is worth mentioning here that two new diffraction peaks appeared after hydrogen peroxide reduction in alkaline medium which are attributed to FeOOH, see inset of Figure B.…”

“…As shown in Figure A–F, the concentration of the directing agent has a significant effect on the morphology of the obtained silver particles. Without using malonic acid, silver particles with ball-like structures were observed with ∼2 μm ball diameter (Figure A), while using low malonic acid concentration (∼0.2 mM) resulted in the formation of small buds (with ∼90 nm average particle size, as estimated from its respective XRD pattern using the Scherrer equation) , on their surfaces, which we called craspedia-globosa flowers (Figure B). Those created buds developed with a further increase in the malonic concentration, where the addition of 0.5 mM malonic acid led to the appearance of silver particles with a chrysanthemum flower-like structure composed of intersected sheets with a ∼72 nm average particle size (Figure C).…”

Electrocatalytic Oxygen Reduction in Alkaline Medium at Graphene-Supported Silver-Iron Carbon Nitride Sites Generated During Thermal Decomposition of Silver Hexacyanoferrate

“…By comparison to literature concerning the application of nanostructured Agbased catalysts for oxygen reduction in alkaline media, it can be concluded that AgFeCN x /GNP800-C has comparable performance relative to such materials as Ag 4 Sn/Vulcan [38], CoOx-Ag/rGO [34], Ag/GO/C [62], Ag/rGO [63], and to some Vulcan-supported Ag nanoparticles [9,64,65]. On the other hand, the activity has been still lower than that characteristic of FeAgPc/KB(600) [37], AgFe lotus /Vulcan [40], and Ag/N-rGO [66] systems. Nevertheless, precise comparison of performances of various catalysts reported in literature is rather difficult, due to differences in morphologies and textures of supports, shapes and sizes of nanoparticles, loadings of catalysts, compositions of electrolytes, and their concentrations.…”

“…When it comes to structural dependence of the oxygen reduction kinetics, it tends to increase according to the following order of planes: (100) < (111) < (110) [31]. It is also noteworthy that fairly active and stable materials have been obtained by combining silver with manganese oxides [32,33], cobalt oxides [34], molybdenum oxides [35], and other transition metals (Co, Cu, Ni, Sn, Fe) [36][37][38][39][40].…”

Nucleation‐Controlled Solution Deposition of Silver Nanoplate Architectures for Facile Derivatization and Catalytic Applications

“…Individual nanoplates are composed of merging, rugged nanobelts (Figure B) and possess {111} basal planes and numerous in‐plane stacking faults, which surface at their edges (Figure S4 in the Supporting Information). If desired, the adsorbed Fe(III) complex can be easily removed in neutral or acidic environment (Figure S5 in the Supporting Information), albeit Fe‐doped Ag nanostructures can show catalytic synergy …”