Structure of Dealloyed PtCu₃ Thin Films and Catalytic Activity for Oxygen Reduction

Abstract

The detailed structure and composition (surface and bulk) as well as catalytic activity for oxygen reduction of electrochemically dealloyed PtCu3 thin films have been investigated. Synchrotron-based anomalous X-ray diffraction (AXRD) reveals that a Pt enriched surface region (∼1.0 nm thick) and a Cu depleted interior (atomic ratio different from that of PtCu3) are formed in the dealloyed film, and we directly observe a compressive lattice strain in the Pt surface region. The dealloyed PtCu3 thin films show a ∼2.4 fold increase in the specific oxygen reduction activity over pure Pt thin films as measured by a rotating disk electrode (RDE). Our results show that the enhanced catalytic activity of the dealloyed Pt−Cu film is primarily due to the compressive strain in the surface layer (ligand effect is very weak). We compare our results on thin films to related results on nanoparticles. These studies provide a better understanding of the structure − composition and structure − activity relationships in Pt-skeleton structures prepared by dealloying base-metal-rich alloys.

Dealloyed PtCu catalyst as an efficient electrocatalyst in oxygen reduction reaction

“…Dealloying by using either chemical or electrochemical methods is well known to induce perturbations in the Pt surface with other non-precious metal-depleted interiors. Strasser and co-workers also reported that electrochemically dealloyed PtCu 3 thin films have a Pt-enriched surface with perturbed thin layers that cover the Cu-depleted interior [21]. In our work, PtCu 3 /C-AT and PtCu 5 /C-AT showed the same fcc structure when compared with Pt catalyst while the Pt lattices were deformed in the XRD results, indicating the existence of a Pt-rich PtCu alloy structure.…”

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

“…Therefore, we may further down-select the scan rate to 20 mV/s which is fairly common in the literature. 4,[29][30][31][32][33]50 ORR activity.-Steady-state.-Practical PEMFCs are typically evaluated for performance using pseudo steady-state conditions and the question arises as to whether it is possible and reasonable to conduct similar measurements in RDE studies and identify the consequent advantages or repercussions. A schematic of the ORR protocol applied for the measurement of pseudo steady-state ORR I-V curves (15 min/point) in both the anodic and cathodic directions is presented in Fig.…”

Ordered alloy formation for Pt3Fe/C, PtFe/C and Pt5.75Fe5.75Cuy/CO2-reduction electro-catalysts

“…Similarly, reported enhancements in the orr activity of originally called Pt "skeleton", then "surface strained" or "core-shell type" catalysts have been assigned to a lowering of the Pt-Pt bond distance [16,17]. Electronic effects have also been suggested to be of benefit for the orr activity.…”

“…Other catalyst architectures referred to as core-shell, surface strained and Pt enriched catalysts have also been suggested [6,7,[12][13][14][15][16][17]. Increases in mass and specific orr activities of such catalysts over Pt-only catalysts have been reported.…”