Preparation and characterization of zinc–aluminum layered doubled hydroxide/ graphene nanosheets composite for supercapacitor electrode

Abstract

Graphene nanosheets were synthesized using the liquid phase exfoliation technique while zinc-aluminum layered doubled hydroxides (ZnAl-LDHs) were fabricated using the chemical bath deposition method. A composite of graphene/Zn–Al LDHs was synthesized and used as an electrode for the supercapacitor . ZnAl-LDHs present a well-standing nanosheets-like structure that covered the entire area of the substrate. The thickness of these nanosheets was found to be between 60 and 80 nm. The SEM images of the graphene/Zn–Al LDHs composite display graphene nanosheets next to the LDHs nanosheets. The optical band gap of this composite was found to be about 4 eV. The obtained electrode exhibited excellent supercapacitive performances with the highest specific capacitance of ∼ 140 F / g along with the maximum energy, and power densities of 15.359 k W K g − 1 and 2.016 W h K g − 1 , respectively. The as-prepared composite showed long-term stability and it retains 97% of the initial capacitance after 2000 charge-discharge cycles. The electrochemical impedance spectroscopy (EIS) results confirm the contribution of both ZnAl-LDHs and graphene in the supercapacitor system. The fabricated electrode using the present simple strategy in this report can be further extended to manufacture other electrodes using other composites from the same family for the upcoming energy storage systems. • Composites of ZnAl-LDHs/graphene was synthesized. • ZnAl-LDHs presents vertically aligned 2D sheets. • Graphene sheets are placed near the obtained ZnAl-LDHs. • The obtained electrode exhibited an excellent supercapacitive performances. • The obtained electrodes presented C P ∼ 140 F / g and PD of ∼ 15.359 k W K g − 1 and ED. ∼ 2.016 W h K g − 1