Polyoxometalate@ZIF Induced CoWO4/WS2@C‑N Nanoflower as a Highly Efficient Catalyst for Zn–Air Batteries

• Published in: ACS applied energy materials 2021-07, Vol.4 (7), p.6892-6902
• Main Authors: Yin, Di, Wang, Ming-Liang, Cao, Yun-Dong, Yang, Xiaopeng, Ji, Su-Yu, Hao, Hui-Ping, Gao, Guang-Gang, Fan, Lin-Lin, Liu, Hong
• Format: Article
• Language: English
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.1c01000

It is crucial to cultivate competent and stable bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). In this work, a high-performance and long-lasting electrocatalyst of CoWO4/WS2@C-N nanocomposite with the unique hierarchical flowerlike superstructure is achieved by sulfuration of porous polyoxometalate@ZIF-67 precursor, in which the polyoxometalate acts as both template and acidic etching agent. The introduction of polyoxometalate also plays a key role in forming the binary CoWO4/WS2 active center during the sulfuration process. CoWO4/WS2@C-N electrocatalyst shows higher electrocatalytic activity than commercial noble-metal catalysts under the same conditions. DFT calculations indicate that both the high adsorption energy for the OH– group and low adsorption energy for O2 on the surface of CoWO4/WS2 sites result in high OER and ORR activity. When CoWO4/WS2@C-N is assembled in a lab-made Zn–air battery as cathode material, the battery shows a higher discharge plateau voltage of 1.46 V and a specific capacity of 664 mA h gZn –1, the behavior of which is comparable to the reported non-noble-metal materials. The synthetic strategy presented in this work not only opens a polyoxometalate-etching-ZIF way to constructing a nanosized heterojunction catalyst but also provides a cost-effective and robust electrocatalyst potentially used in practical Zn–air batteries.