Engineering multi-hollow PtCo nanoparticles for oxygen reduction reaction via a NaCl-sealed annealing strategy

• Published in: Journal of alloys and compounds 2021-12, Vol.884, p.161063, Article 161063
• Main Authors: Nie, Yao, Deng, Jianghai, Jin, Wenting, Guo, Wenlong, Wu, Guangping, Deng, Min, Zhou, Jiajun, Yang, Ruolan, Zhang, Shuo, Wei, Zidong
• Format: Article
• Language: English
• Subjects: Annealing; Cobalt; Intermetallic compounds; Multi-hollow PtCo alloy; NaCl-sealed annealing; Nanoparticles; Nanoscale Kirkendall mitigation; Oxygen reduction reaction; Oxygen reduction reactions; Platinum; Platinum base alloys
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.161063

•Solid Pt NPs can be converted into multi-hollow PtCo alloys by annealing a NaCl-sealed Pt/C@polydopamine-Co2+ system.•NaCl act as a sealed nanoreactor to provide key conditions for nanoscale Kirkendall migration between Pt and Co atoms.•Rigid NaCl can prevent fast PDA loss and serious NPs sintering, ensuring highly active specific surface area of products.•The water-removability of NaCl makes the present synthesis a facile and green method.•The obtained h-PtCo@NC affords much higher specific and mass activity for ORR than commercial Pt/C. A thermal activated Kirkendall mitigation between Pt and Co atoms can happen within a NaCl-sealed Pt/C@polydopamine-Co2+ system, leading to form multi-hollow PtCo NPs without serious sintering. [Display omitted] Hollow-structuring of Pt-based nanoparticles (NPs) is among the most effective strategies for reducing Pt utilization whilst maintaining good performance for oxygen reduction reaction (ORR). This work presents a NaCl-sealed annealing strategy to directly convert solid Pt NPs into multi-hollow PtCo alloys with a Pt-rich surface. By annealing a NaCl-sealed Pt/C@polydopamine-Co2+ system, the essential conditions for forming hollow Pt alloys can be easily equipped and a thermal activated nanoscale Kirkendall mitigation between Pt and Co atoms can consequently let inner solid Pt accomplish alloying and hollow-structuring. Serious sintering of NPs during thermal annealing can be efficiently avoided owing to the protection of outer rigid NaCl. The whole procedures is template-free and the final catalysts can be easily released from NaCl by just water washing, making the present synthesis a facile, green and versatile method. The final obtained multi-hollow PtCo NPs featured with a nitrogen-doped carbon coating afford much enhanced ORR activity and stability than benchmark commercial Pt/C.