Designed Synthesis of Well‐Defined Pd@Pt Core–Shell Nanoparticles with Controlled Shell Thickness as Efficient Oxygen Reduction Electrocatalysts

Abstract

Improving the electrocatalytic activity and durability of Pt-based catalysts with low Pt content toward the oxygen reduction reaction (ORR) is one of the main challenges in advancing the performance of polymer electrolyte membrane fuel cells (PEMFCs). Herein, a designed synthesis of well-defined Pd@Pt core-shell nanoparticles (NPs) with a controlled Pt shell thickness of 0.4-1.2 nm by a facile wet chemical method and their electrocatalytic performances for ORR as a function of shell thickness are reported. Pd@Pt NPs with predetermined structural parameters were prepared by in situ heteroepitaxial growth of Pt on as-synthesized 6 nm Pd NPs without any sacrificial layers and intermediate workup processes, and thus the synthetic procedure for the production of Pd@Pt NPs with well-defined sizes and shell thicknesses is greatly simplified. The Pt shell thickness could be precisely controlled by adjusting the molar ratio of Pt to Pd. The ORR performance of the Pd@Pt NPs strongly depended on the thickness of their Pt shells. The Pd@Pt NPs with 0.94 nm Pt shells exhibited enhanced specific activity and higher durability compared to other Pd@Pt NPs and commercial Pt/C catalysts. Testing Pd@Pt NPs with 0.94 nm Pt shells in a membrane electrode assembly revealed a single-cell performance comparable with that of the Pt/C catalyst despite their lower Pt content, that is the present NP catalysts can facilitate low-cost and high-efficient applications of PEMFCs.

Carbon-Supported Pt-Based Alloy Electrocatalysts for the Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells: Particle Size, Shape, and Composition Manipulation and Their Impact to Activity

“…These Pt 3 Co/C catalysts exhibited over 200% increase in mass activity and over 300% increase in specfic activity when compared with disordered Pt 3 Co alloy nanoparticles as well as Pt/C particles. In addition to Co, other metals, such as Au, 284 Ag, 285 Cu, 214 Ni, 382 and Pd, 383,384 have also been used as the core inside a Pt shell.…”

Shell-Thickness-Controlled Synthesis of Core-Shell Pd@Pt Nanocubes and Tuning of Their Oxygen Reduction Activities

“…Adzic et al 17 conducted experiments using a Pt monolayer-coated metal electrode and found that the unique activities are attributed to the optimized O 2 binding strength and the d-band center position. Based on this finding, Han et al 18 synthesized a precisely controlled Pt shell with a thickness of 0.4-1.2 nm on Pd nanoparticles (NPs) of 6 nm. Furthermore, Pd@Pt NPs with a shell thickness of 0.94 nm, were found to exhibit ORR performance superior to that of commercial Pt catalysts in an HClO 4 electrolyte.…”

“…Furthermore, Pd@Pt NPs with a shell thickness of 0.94 nm, were found to exhibit ORR performance superior to that of commercial Pt catalysts in an HClO 4 electrolyte. 18 Zhang et al successfully prepared dendritic-Pt-shell coated Pd nanostructures using a microwave method with a fixed Pd/Pt molar ratio of 1:3. 19 They found that the ORR kinetics was faster by the activity of these nanostructures than that by pure Pt nanodendrites or Pd naocubes in a 0.5 M H 2 SO 4 electrolyte.…”

Fuel Cell Performance of Palladium-Platinum Core-Shell Electrocatalysts Synthesized in Gram-Scale Batches

“…Core-shell catalysts that consist of an ultrathin Pt shell and a Pd core have been proposed as candidates to replace pure Pt. [6][7][8][9][10] In addition to the high Pt utilization and lower cost of the Pd core, strain and electronic effects induced by the Pd core can enhance the activity of the Pt shell for the ORR, 11 leading to a greater activity per mass of Pt than expected based on the utilization improvement alone.…”