Structural Transformation of Pt–Ni Nanowires as Oxygen Reduction Electrocatalysts to Branched Nanostructures during Potential Cycles

Abstract

We report the preparation, oxygen reduction reaction (ORR) electrocatalytic activity, and structural transformation of Pt–Ni nanowires (NWs) during potential cycles in the presence and absence of Pt–Ni nanoparticles (NPs). The ORR activity of NWs increases over 25000 potential cycles in the presence of NPs, involving the structural transformation of NWs to branched nanostructures assisted by Ostwald ripening of NPs. This structural transformation is coupled with the surface electronic structural change, as confirmed by in situ X-ray absorption spectroscopy and carbon monoxide stripping voltammetry, leading to catalytic activity improvement and Pt dissolution suppression. Although a similar structural transformation was also observed even in the absence of NPs, greater amounts of Pt were dissolved during potential cycles. These results indicate that the structural transformation is intrinsic to Pt-based NWs but the structural transformation of NWs assisted by Ostwald ripening of NPs is beneficial to suppress the Pt dissolution. The concept of the structural optimization of nanostructured catalysts assisted by Ostwald ripening of NPs under potential cycles will guide us to develop highly active and durable Pt-based electrocatalysts and phase-engineered nanomaterials.

Pt‐Anchored‐Zirconium Phosphate Nanoplates as High‐Durable Carbon‐Free Oxygen Reduction Reaction Electrocatalyst for PEM Fuel Cell Applications

“…[ 38 ] Similarly, Pt–Ni wire which transformed into the branched nanostructure during the potential cycling, and the mass activity was found to be increased from 0.15 A mg −Pt to 0.22 A mg −Pt after 25 K cycles. [ 39 ] We have carried out the TEM analysis of the ZrP@Pt after ADT, and the structure is found to be stable after 3000 start‐stop cycles, as shown in Figure S11 (Supporting Information). The stability can be explained by the strong interaction between the phosphate group and the Pt nanoparticles.…”

Platinum–Nickel Alloy Nanowire Electrocatalysts Transform into Pt-Skin Beads-on-Nanowires Keeping Oxygen Reduction Reaction Activity During Potential Cycling

“…PtNi NWs were synthesized using a modified procedure that was previously reported. 3 Vulcan XC-72R (ca. 3 mg) and PtNi NWs (ca.…”

“…NW 433 K /C was also changed similarly to waved and branched structures, as previously reported. 3 In contrast, NW 553 K /C was converted into a branched structure with no wave structures or beads. Because the NW 493 K /C catalyst has both sufficient Ni contents and coexisting PtNi NPs, the structural change could be mediated by the dissolution−redeposition process under potential cycles involving the coexisting PtNi NPs.…”

A Review of One‐Dimensional Nanomaterials as Electrode Materials for Oxygen Reduction Reaction Electrocatalysis

“…In addition to the effects of structural changes in the nanowires themselves, the branched structures grown by the nanowires induced with external conditions can also enhance their electrocatalytic performance. Kato et al [110] prepared PtÀ Ni NWs with PtÀ Ni NPs as ORR electrocatalysts. And transformed the NPs into branched nanostructures by Ostwald ripening during potential cycling (Figure 8c).…”