Effects of Catalyst Processing on the Activity and Stability of Pt–Ni Nanoframe Electrocatalysts

Abstract

Pt-based alloys have shown great promise as cathodic catalysts for cost-effective proton-exchange membrane fuel cells. Post-synthesis treatment has been recognized as a critical step to improve the catalytic performance of Pt-based alloys. Here, we present the effects of catalyst processing on the catalytic behavior of Pt-Ni nanoframe electrocatalysts in oxygen reduction reaction. The Pt-Ni nanoframes were made by corroding the Ni-rich phase from solid rhombic dodecahedral particles. A total of three different corrosion procedures were compared. Among them, electrochemical corrosion led to the highest initial specific activity (1.35 mA cm at 0.95 V versus reversible hydrogen electrode) by retaining more Ni in the nanoframes. However, the high activity gradually went down in a subsequent stability test due to continuous Ni loss and concomitant surface reconstruction. On the other hand, the best stability was achieved by a more-aggressive corrosion using oxidative nitric acid. Although the initial activity was compromised, this procedure imparted a less-defective surface, and thus, the specific activity dropped by only 7% over 30 000 potential cycles. These results indicate a delicate trade-off between the activity and stability of Pt-Ni nanoframe electrocatalysts. The obtained understanding of how to balance the activity-stability trade-off via catalyst processing can be generalized to other Pt-based alloys.

Pt–Ni Seed-Core-Frame Hierarchical Nanostructures and Their Conversion to Nanoframes for Enhanced Methanol Electro-Oxidation

“…This size decrease could be attributed to the presence of Pt-Ni co-reduction from homogeneous nucleation in addition to heterogeneous nucleation on the Pt seeds as the concentration of Ni(acac) 2 increases. The homogeneous nucleation depletes the concentration of both precursors for heterogeneous growth, resulting in the reduction of the particle size similar to those reported in the literature from homogeneous nucleation [11][12][13]15,16].…”

“…In this work, we reported a seeded co-reduction method to synthesize the rhombic dodecahedral, hierarchical structure. Different from the previously-reported one-pot synthesis [11][12][13]15,16], the heterogeneous nucleation of Ni on Pt seeds dominated, followed by selectively deposition of Pt on the edges and corners of the resulting seed-core rhombic dodecahedra to yield the seed-core-frame structures. The reaction mechanism was further investigated in detail in order to elucidate the important parameters for controlling the morphology of the complex structure.…”

“…More recently, an open-framework, Pt 3 Ni nanoframe, was demonstrated an enhancement factor of 36 in mass activity and 22 in specific activity, respectively for ORR compared to Pt/C due to the large surface areas from both the interior and exterior of the frame structure [11,12]. The electrocatalytic activity of nanoframes could be further tuned by the anisotropic phase segregation of migration of Pt during synthesis and by controlling the architecture of the nanoframes [13][14][15]. The shape of the nanoframes could be tuned by the use of different surface ligands to yield tetrahedral and rhombic dodecahedral nanoframes, respectively [16].…”

Oxidatively induced exposure of active surface area during microwave assisted formation of Pt3Co nanoparticles for oxygen reduction reaction

“…6b at 0.06-0.07 V vs. RHE can sometimes emerge in Pt NPs with incorporated transition metals, oen seen in provided H UPD curves as a peak (or bump) below 0.1 V vs. RHE. 14,26,62 Assuming that this is the reason for the peak, being more pronounced in Pt 3 Co/C*, it infer that near-surface transition metal species is less common in Pt 3 Co/C than Pt 3 Co/C*, supporting the above discussion on the occurrence of surface Pt migration during the secondary MW treatment. In addition, the disappearance of this feature aer degradation can likely be directly attributed to de-alloying and re-installment of a more "Pt-like" surface.…”

Nanostructure Optimization of Platinum-Based Nanomaterials for Catalytic Applications

“…The nanoframes, possessing open structure and more accessible surfaces, have received the researchers’ attention in recent years. Many literatures have proven than the fabrication of nanoframes is a better choice to construct excellent electrocatalysts [ 37 , 98 , 112 , 113 , 114 ]. Chen et al firstly synthesized PtNi 3 polyhedrons in oleylamine that had a rhombic dodecahedron morphology and uniform size distribution [ 115 ].…”