Compositional Evaluation of Coreduced Fe–Pt Metal Acetylacetonates as PEM Fuel Cell Cathode Catalyst

Abstract

Platinum−iron nanoparticles were produced by solvothermal coreduction of organic Fe and Pt precursor compounds and supported on conventional Vulcan XC 72. Evaluation of oxygen reduction performance reveals a highly active surface with up to 5 times the specific activity of commercial Pt−Vulcan measured in O 2 -saturated 0.1 M HClO 4 . A particle size of 5.5 nm for the best performing sample, produced from an initial metal ratio of 1:1, provided 28% higher mass activity than the commercial reference. Membrane electrode assemblies, optimized for both H 2 /O 2 and direct formic acid fuel cells, were produced, and the PEM fuel cell cathodic performance displayed results with similar enhancements as its ex situ measured mass activity, although a delamination of the catalyst layer from the membrane could be observed even when employing a hot-pressing procedure during MEA fabrication. Physical characterizations including X-ray photoelectron spectroscopy and in situ X-ray diffraction reveal oxidized states of Fe incorporated into the disordered face-centered cubic Pt nanoparticles, supported by composition-dependent morphological changes as observed by transmission electron microscopy. The provided insight into fuel cell performance as well as CO-oxidation attributes are expected to assist in selecting suitable applications and operating conditions for such FePt type nanoparticles.

Microwave-Induced Structural Ordering of Resilient Nanostructured L10-FePt Catalysts for Oxygen Reduction Reaction

“…In solvothermal processes, this phenomenon is rationalized by initial formation of Fe-rich seeds promoting gradual Pt precipitation and deposition. 5,35 Whether this explanation also satisfies our current synthesis conditions of rapid coreduction in the dry phase is unclear. After annealing (FePt(1:1)/C), the particle size shows a relatively small increase in size from ∼2.4 to ∼2.9 nm in conjunction with the increase in order parameter (see Supporting Information Figure S5), manifesting a remarkable resilience toward crystallite growth, which is commonly caused by either Ostwald ripening or support-detachment followed by migration and coalescence.…”

“…A widening of the peaks corresponding to a decrease in particle sizes from ∼3 to ∼2 nm correlate to an increase in Fe/Pt ratio, indicating that the average NP size can be directly tuned by the fraction of the Fe precursor. In solvothermal processes, this phenomenon is rationalized by initial formation of Fe-rich seeds promoting gradual Pt precipitation and deposition. , Whether this explanation also satisfies our current synthesis conditions of rapid coreduction in the dry phase is unclear. After annealing (FePt(1:1)/C), the particle size shows a relatively small increase in size from ∼2.4 to ∼2.9 nm in conjunction with the increase in order parameter (see Supporting Information Figure S5), manifesting a remarkable resilience toward crystallite growth, which is commonly caused by either Ostwald ripening or support-detachment followed by migration and coalescence. ,− This observation is validated by experiments where we annealed the FePt(1:1)/C* in a conventional oven, resulting in an increase in a particle size of only ∼0.6 nm (particle size 3 nm) at 700 °C, likely owing to unusually firm adherence to the carbon support.…”

“…Alloying Pt with late transition-metals (Fe, Co, and Ni) can tune the O 2 adsorption energy so that the ORR performance is improved, and because these nanoparticles (NPs) are diluted with a nonprecious metal, the Pt-specific mass activity can reach impressive levels. , The FePt alloy is one such catalyst with beneficial synergistic effects toward ORR, − where near 1:1 atomic ratios generally show near optimum performance. The FePt (1:1) lattice may exist in either a disordered face-centered cubic (fcc) or as a structurally ordered face-centered tetragonal (fct) phase, where the latter normally displays greater ORR activity and durability. − However, to transform fcc NPs into the fct structure, typically a temperature around 600 °C is required.…”

Raspberry-like Pd3Pb alloy nanoparticles: superior electrocatalytic activity for ethylene glycol and glycerol oxidation

“…Since the electrocatalytic property of Pt-based nanomaterials can be tuned by manipulating the precursors, reaction conditions and preparation methods, one promising strategy to improve the electrochemical performance is alloying Pt with a second transition metal which holds advantages comparing with monometallic catalysts owing to the existence of synergistic effect between the two metals. A series of measures have been utilized in alloying Pt with Ni, 13,14 Cu, 15 Pd, 16 Fe, 17 and Pb. [18][19][20] Huang et al 19 successfully prepared platinum-lead concave nanocubes with excellent electrocatalytic performance towards methanol oxidation, which is contributed by the synergistic effect of Pt-Pb alloys.…”

Oxidatively induced exposure of active surface area during microwave assisted formation of Pt3Co nanoparticles for oxygen reduction reaction

“…In fact, theoretical and practical studies have shown that modication of the electron conguration within the Pt lattice can dramatically alter the surface adsorption of oxygen in a favorable direction such that the ORR results in a lowered overpotential. 7,8 This can be achieved by alloying Pt into binary or ternary congurations with 3d type transition metals such as Fe, [9][10][11] or Co, [15][16][17] which may enhance the ORR properties by mechanisms involving the creation of more close-packed surface facets of the face centered cubic (fcc) Pt lattice and/or inducing ligand effects. It is clear that this approach is highly convenient as it also dilutes the Pt within the nanoparticle core and may thus further contribute to an enhanced Pt mass activity.…”