Simple synthesis of highly uniform bilayer-carbon nanocages

Abstract

A simple, highly scalable method of obtaining densely-packed, three-dimensional structures of interconnected, bilayer, hollow carbon nanocages, is reported. High-quality nanocages with well controlled wall thickness are synthesized via catalytic templating on densely-packed, mono-sized nickel nanoparticles, nucleating in situ during short, mid-temperature annealing of an inexpensive precursor obtained from nickel acetate and citric acid. Following nickel dissolution, large monolithic grains of densely packed networks of carbon nanocages are obtained and extensively characterized. In situ TEM experiments are conducted to elucidate the mechanism of nanostructure formation, and a geometrical model is proposed to explain the high specific surface area and its relation to the nanocages' diameter and wall thickness. These nanocages, with their bilayer structure, unimodal pore size distribution and pore size of ∼2.5 nm, approach the theoretical capacity of undoped bilayer graphene when tested in an electrochemical double-layer capacitor system. Our synthesis approach provides a facile method for tuning nanocages' morphology and efficiently doping them, creating an effective enhancement of capacity and properties suitable for a broad range of new energy and environmental applications.