Combustion-driven synthesis route for bimetallic Ag-Bi nanoparticle-anchored carbon nanotube electrodes for high-performance supercapacitors

Abstract

Bimetallic nanostructures within carbon-based materials can overcome the fundamental limits of energy materials, which cannot be obtained using a single material. However, their synthesis involves time-consuming and complex processes that cause phase/interface segregation and non-uniformly distributed metal elements. Herein, we report a facile combustion-driven synthesis for bimetallic Ag-Bi nanoparticle (NP)-anchored carbon nanotube (CNT) electrodes. One-step combustion wave passing through freestanding films comprising Ag2O and Bi powders, nitrocellulose layers within CNTs enables high-density thermochemical reactions in seconds. The rapid heating-cooling rates induce the formation of liquefied Ag-Bi and trapping of metastable Ag-Bi phases at the carbon surfaces, thereby synthesizing homogeneously mixed bimetallic Ag-Bi NPs anchored on the CNTs, along with smaller diameters (similar to 20 nm) and high distribution density. A supercapacitor electrode employing them exhibits outstanding specific capacitance and retention (1372-1093 Fg(-1) at 2-5 mVs(-1), and 101.3% of the stabilized capacitance after 10,000 cycles at 100 mVs(-1)). This was attributed to the large active site surface area from the small diameters and high distribution density of the bimetallic Ag-Bi NPs by low surface energy, and highly stable adhesion to the CNTs. The synthesis strategy can be extended to a scalable fabrication method of various multi-metallic nanostructures for versatile electrochemical electrodes and catalysts.