High performance graphene composite microsphere electrodes for capacitive deionisation

Graphene oxide/resorcinol–formaldehyde microsphere (GORFM) was synthesised by a simple-inverse suspension polymerisation under ambient pressure drying and the graphene composite microsphere (GCM) was obtained by carbonisation in a nitrogen atmosphere. The morphologies and microstructures of GORFM and GCM samples were characterised by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and surface area analysis. The results showed that the diameters of GORFM were controlled in the range of 5–10 μm with perfect sphericity. The inner layer of GORFM was composed of resorcinol–formaldehyde (RF) particles, and the outer layer was the wrinkled GO sheets intercalated with RF through chemical and physical interactions. The GCM-1.5 sample achieved the highest specific surface area of 1128 m²/g and the mesopore area was 699 m²/g. The electrochemical behaviours of GCM as an electrode were investigated by cyclic voltammograms, electrochemical impedance spectroscopy and capacitive deionisation (CDI). The specific capacitance and electrosorption capacity of GCM-1.5 was 290.2 F/g and 33.52 mg/g, respectively. The current efficiencies were in the range of 77.75–81.41%. These results implied that GCM had a potential application in CDI due to its low-cost and high performance.