Rational Design of Carbon-Supported Platinum–Gadolinium Nanoalloys for Oxygen Reduction Reaction

Abstract

Highly active and long-term stable electrocatalysts for the oxygen reduction reaction (ORR) of proton-exchange membrane fuel cells are required for alignment of material properties with sectoral demand. Herein, we have produced a series of Pt x Gd/C electrocatalysts using the carbodiimide complex route, in which the gadolinium content in the final product was systematically varied. The results reveal that the Pt/Gd ratio influences the crystalline structure, the particle size, the near-surface chemistry, and, therefore, the electrochemical activity toward ORR. A morphological transition, from solid nanoparticles to porous architecture, takes place as the Gd concentration increases, where 10 nm is the critical size for transition. Moreover, the mass activity toward the ORR displays a volcano-shaped trend, reaching a maximum value at the composition of Pt4.7Gd. This contribution identifies key properties of the Pt x Gd/C nanostructures that are essential to boost the ORR activity and durability, along with remaining issues that must be addressed, such as the undesirable formation of porous architecture.

Enhancing the activity and stability of carbon-supported platinum–gadolinium nanoalloys towards the oxygen reduction reaction

“…This effect is pronounced in NPs with sizes> 10 nm. 11 Although the population of these structures is attenuated with the wash under N 2 -atmosphere, in some regions we have observed porous NPs (Fig. S3 † ).…”

“…This feature is related to the crystalline phase (cubic Pt 2 Gd) and the formation of porous nanoarchitectures which are easily degraded under the harsh ORR conditions (nanoalloy segregation, metal dissolution, morphology transitions, etc. ), 11 resulting in significant performance decay. The formation of such sponge-like structures has been also reported for nanoparticulate systems such as Pt–Ni 12 and Pt–Co, 13 where they compromise the activity/stability benefits of the alloyed systems.…”

“…Following our previous contribution, 11 in which we have identified the optimal Pt:Gd composition, Pt x Gd NPs dispersed over conventional carbon Vulcan XC-72 were prepared. After the synthesis reaction (see details in the ESI † ), the XRD pattern of the as-prepared material, Fig.…”

“…1c , however, show that porous nanoarchitectures are formed through the leaching under air atmosphere. We have reported that the nanopore formation initiates where Gd is relatively abundant in the particle, 11 and its dissolution can proceed until Pt is sufficiently available to form a protective layer and stabilise the structure. This effect is pronounced in NPs with sizes> 10 nm.…”

“…We have previously reported the formation of the Pt overlayer in this system, which supports this observation. 11 …”