One-dimensional heterostructures of polyoxometalate-encapsulated carbon nanotubes for enhanced capacitive energy storage
Sheng Zhu, Xiaoxin Yang, Yixi Yao, Xinrui Zhang, Lan Li, Xiao Wang, Gaoyi Han, Yan Li
Abstract
Carbon nanotubes are promising electrode materials for electrochemical capacitive energy storage. Here, we report a host-guest strategy to construct one-dimensional heterostructures by encapsulating redox-active polyoxometalate molecular clusters within single-walled carbon nanotubes. The electron transfer from nanotubes to clusters loosens π−π stacking of carbon nanotubes, leading to improved dispersion and higher electrical double-layer capacity. Besides, the nanoconfinement effect of carbon nanotubes not only facilitates electron transfer for inner redox-active polyoxometalates but also protects them from chemical degradation. Typically, the hybrid redox material delivers a high specific capacity of 328.6 F g−1 at 10 mV s−1 in phosphoric acid electrolyte and a prominent rate capability with 82.1% capacity retention at 500 mV s−1. The assembled supercapacitor exhibits maximum energy density of 33.4 Wh kg−1 and long-term stability with 91.3% of the initial capacity retained over 10,000 cycles. This study underlines the potential of redox-driven encapsulation strategies in developing high-performance energy storage materials.