Seed-Mediated Growth of Pt on High-Index Faceted Au Nanocrystals: The Ag Lining and Implications for Electrocatalysis

Abstract

Bimetallic Au@Pt nanocrystals (NCs) offer a unique combination of plasmonic and catalytic properties and are a growing field of research. Herein, we report an unusual observation in the behavior of silver ions (Ag + ), which was found to play a dominant role in dictating the Pt deposition in a seed-mediated growth method. While the literature is replete with various instances of Ag-assisted Pt deposition whereby higher concentration of Ag + translates into a thicker Pt shell, in the present study, contradictory observations were made. In the presence of lower amounts of Ag + , thick Pt shells were visualized, while at higher concentrations of Ag + , the extent of Pt deposition via the galvanic replacement reaction was reduced. Additionally, the presence of Ag was deemed necessary for the Pt deposition to take place, either in the form of an underpotential deposition layer on the Au NCs or by introducing Ag + in the growth solution. We have demonstrated our findings on two different Au NCs enclosed with high-index facets, concave cuboid, and elongated tetrahexahedra, which mirror similar observations and provide generality to our claim. To the best of our knowledge, the time required for Pt deposition on the Au core in the present work is the least among the reported seed-mediated routes. Furthermore, this work, besides presenting a facile and general route for the amalgamation of catalytic and plasmonic properties in hybrid Pt−Au NCs, sheds light on the mechanistic aspects of Ag-assisted wet-chemical generation of bimetallic Au@Pt NCs. The overall electrocatalytic performance of our Au@Pt NCs toward the oxygen reduction reaction was realized to be impressive.

Deriving multi-metal nanomaterials on metal–organic framework platforms for oxygen electrocatalysis

“…This method allows for the full integration of MOF advantages, leading to substantial synergistic effects. [149][150][151] Huang et al have devised a seed-mediated growth method approach to create CoFe 2 O 4 @CuO microcages originating from core-shell dual-MOF heterostructures (Fig. 5A and B).…”

Seed-Mediated, Shape-Controlled Synthesis Methods for Platinum-Based Electrocatalysts for the Oxygen Reduction Reaction—A Mini Review

“…This can be explained due to a lattice mismatch between Pt and Au and the strong Pt-Pt bonds. Roy et al (2021) achieved the smooth coverage of Pt whilst maintaining the seed morphology through the addition of Ag + ions within an optimum range. Ag + ions deposit onto the Au surface through under potential deposition and facilitate the deposition of Pt through either direction to preferential sites, or by galvanic replacement.…”

“…Upon varying the amount of Pt precursors, it was found that the synthesized Au@Pt CCB NCs with high Pt loading displayed better activities for the ORR with higher onset potentials (Figure 2A), furthermore, the highest Pt-loading materials displayed better stability than commercial Pt/C after 5,000 cycles of accelerated stress test (shifts of 28 and 39 mV respectively). (Roy et al, 2021).…”