Insights on the effect of incorporating ZIF-8 carbon in enhancing the electrochemical capacitance of thermally reduced graphene oxide

Composites based on low-cost carbonaceous nanomaterials – with excellent electrochemical energy storage properties – have gained significant research interest for the development of efficient supercapacitor technologies. It is often observed that the morphology, composition and surface modifications of the carbon-based composites significantly impact their overall charge storage behaviour. To gain deeper insights into these complicated energy storage mechanisms with the alteration in carbon constituents, herein a systematic investigation is carried out with a series of electrode materials prepared in-situ from mixtures (ink) of thermally reduced graphene oxide (T-rGO) and carbonized zeolitic imidazolate framework (CZ-8) taken in various weight ratios. The conducted electrochemical measurements (voltammetry and impedance spectroscopy) suggest that the incorporation and increment of the porous CZ-8 content in the T-rGO sheets drastically improves the specific capacitance of the T-rGO|CZ-8 composite because of lowered charge-transfer resistance (R CT ). The excellent synergy between the 3D porous CZ-8 particles and 2D laminar T-rGO sheets (confirmed from the diffraction patterns and microscopic images) leads to an enhanced diffusion of the electrolyte ions to the composite surface allowing the T-rGO|CZ-8 composites to reach a high specific capacitance of >215 F‧g −1 at a current density of 0.5 A‧g −1 in 1.0 M KOH electrolyte. When tested in a two-electrode configuration, the fabricated T-rGO|CZ-8 (50:50)||T-rGO|CZ-8 (50:50) device delivered a decent energy density of 4.78 Wh⋅kg −1 at a power density of 150 W⋅kg −1 . It is established that the presence of CZ-8 particles not only prevents the restacking of the T-rGO sheets but also enhances the pseudocapacitive contribution leading to improved charge storage capacity at high current densities and excellent electrochemical stability during prolonged charge-discharge cycles. • T-rGO|CZ-8 composite electrodes are fabricated following a simple in-situ mixing technique. • The T-rGO|CZ-8 (90:10) electrode exhibits a maximum capacitance of 255 F. g −1 . • Excellent retention of capacitance is observed with the T-rGO|CZ-8 (50:50) sample. • Incorporation of CZ-8 enhances the capacitance of T-rGO and imparts electrochemical stability. • The low R CT of the T-rGO|CZ-8 composites are anticipated for their excellent capacitance.