A sponge-templated sandwich-like cobalt-embedded nitrogen-doped carbon polyhedron/graphene composite as a highly efficient catalyst for Zn-air batteries

• Published in: Nanoscale 2020-01, Vol.12 (2), p.973-982
• Main Authors: Cai, Jia-Jun, Zhou, Qing-Yan, Liu, Bing, Gong, Xiao-Fei, Zhang, Yun-Long, Goh, Kokswee, Gu, Da-Ming, Zhao, Lei, Sui, Xu-Lei, Wang, Zhen-Bo
• Format: Article
• Language: English
• Subjects: Carbon; Catalysts; Graphene; Metal air batteries; Metal-organic frameworks; Nitrogen; Noble metals; Open circuit voltage; Oxygen reduction reactions; Polyhedra; Polyurethane resins; Sandwich structures; Stability; Structural hierarchy; Zeolites; Zinc-oxygen batteries
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c9nr09020g

Non-noble metal materials are regarded as the most promising catalysts for the oxygen reduction reaction (ORR) to overcome the inherent defects of Pt-based catalysts, like high cost, limited availability and insufficient stability. Here, we fabricate sandwich-like Co encapsulated nitrogen doped carbon polyhedron/graphene (s-Co@NCP/rGO) via a facile and scalable strategy by loading Co-based zeolitic imidazolate framework (ZIF-67) and graphene oxide (GO) layers individually on a polyurethane (PU) sponge template. The 3D sandwich structure is maintained with the assistance of the sponge template, which promotes the uniform dispersion of ZIF-67-derived Co embedded nitrogen doped carbon polyhedra (Co@NCP) and prevents the graphene plates from agglomerating during the annealing process. The final product demonstrates considerable catalytic performance for the ORR with a half-wave potential of 0.85 V, preferable stability and increased poisoning tolerance by comparison to 20 wt% Pt/C, which stems from the 3D sandwich-like structure, N/Co-doping effect, large accessible surface area and hierarchical porous structures. The excellent ORR performance of the catalysts means that they can be utilised in a Zn-air battery as cathode catalysts. During such a demonstration, s-Co@NCP/rGO shows a high open-circuit voltage of 1.466 V, remarkable long-term durability and an outstanding peak power density of 186 mV cm −2 , which shows its high potential as a prospective alternative for widespread practical application in the field of non-noble metal ORR catalysts. Sandwich-like Co-embedded N-doped carbon polyhedron/graphene with a hierarchical porous structure was fabricated through a solution dip-coating method using sponge templates.