Core–Shell CuPd@NiPd Nanoparticles: Coupling Lateral Strain with Electronic Interaction toward High-Efficiency Electrocatalysis

Abstract

Geometric structure and chemical composition are two critical factors that determine the electronic properties of an active metal favorable for a given catalytic reaction. In this scenario, we develop a wet-chemistry method to construct core−shell nanoentities consisting of a CuPd alloy core and a NiPd alloy shell, termed as CuPd@NiPd, which involves the synthesis of CuNi alloy seeds, and a subsequent galvanic replacement reaction with Pd 2+ precursors in an organic medium at elevated temperature. In these unique core−shell nanostructures, the compressive lattice strain between core and shell regions and the electronic interaction between Pd and transitional elements could be coupled together to lead to a downshift of the d-band center of Pd sites, thus endowing them with good activity for catalyzing ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR). In particular, at an appropriate Pd/Cu precursor ratio of 1/1, the as-prepared core−shell CuPd@NiPd nanoparticles exhibit a mass activity of 5.1 A mg −1 for EOR and a half-wave potential of 0.91 V for ORR at room temperature in an alkaline medium, outperforming alloy CuPd, NiPd counterparts, commercial Pd/C, and the vast majority of recently reported Pd-based electrocatalysts.

Ultrafine SnPd Nanoalloys Promise High-Efficiency Electrocatalysis for Ethanol Oxidation and Oxygen Reduction

“…In theory, alloying a second metal into Pd would induce geometric and ligand effects that change its electrocatalysis for a given electrochemical reaction, e.g., ORR and EOR in this study. − The former refers to the lateral strain effect that is induced by different atomic sizes or arrangements, while the latter is caused by charge transfer or shift between the two dissimilar surface metal atoms. Both of them could alter the catalytic performance of the Pd metal by affecting its electronic band structure. − In the case of SnPd nanoalloys, the modification of geometric and ligand effects induced by Sn atoms on the Pd electronic band structure may offset, meaning that the alloys could maximize their catalytic advantages only at an optimal Sn/Pd ratio.…”

Galvanic replacement reaction to prepare catalytic materials

“…The retention of 94% to its initial mass activity further indicated their excellent ORR stability (Figure 10i). Along with the chemical compositions, the geometric structure of the catalyst is also beneficial in improving the ORR activity 119 . The GRR between the CuNi alloy and Pd 2+ ions in the solution leads to the formation of CuPd alloy core and NiPd alloy shell (CuPd@NiPd).…”

Combined Rotating Disk Slurry Electrodeposition–Spontaneous Galvanic Displacement for Pt-M (M = Co, Ni, and Cu) Catalyst Synthesis for the Oxygen Reduction Reaction in Alkaline Media

“…Non-PGM−PGM alloys, 7 core−shells, 8 and non-precious metal catalysts 9 reducing the amount of PGMs needed. Specifically, Pt alloyed with first-row transition metals are among the most active materials�the fermi level of Pt 4d and 4f orbitals is lowered while Pt 5d orbital vacancies are increased� promoting enhanced Pt-O 2 interactions in the ORR.…”

“…Non-PGM–PGM alloys, core–shells, and non-precious metal catalysts are the leading contenders to replace PGM catalysts. The combination of PGMs with a non-precious metal has been demonstrated to improve ORR performance while reducing the amount of PGMs needed.…”