A three-dimensional Ag nanoparticle/graphene hydrogel composite and its application as an improved supercapacitor’s electrode

In this work, pure graphene hydrogel (GH) and graphene/Ag nanoparticle (GH-AgNP) composite hydrogels with various wt% of 0.01, 0.1, 1, 10, 30, and 50% Ag were produced. Samples were characterized by XRD, Raman spectroscopy, and SEM analysis. Supercapacitor electrodes based on pure GH and GH-AgNP composite hydrogel were fabricated without the use of any additives and adhesives, and their electrochemical behaviors were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrical impedance spectroscopy (EIS). High specific capacitances of 252 F/g and 180 at scan speeds of 10 and 200 mV/s for pure hydrogel and specific capacitances of 260 to 143 F/g for composite hydrogels were observed, respectively. GCD analyses implied that GH-AgNP composites possessed lower internal resistance (IR), therefore better rate capabilities. Consequently, it seems that the optimization of GH-AgNP composite hydrogels is an effective way of reducing the supercapacitor’s internal resistance and thereby increasing the power and improving supercapacitor performance. It was observed that the addition of Ag nanoparticles to graphene hydrogels, even with low wt%, significantly reduces the charge transfer resistance. In a GH-AgNP sample with an Ag/GO ratio of 1%, the charge transfer resistance value was reduced by 77%, while the specific capacitance was reduced by just 8%.