In this study, at first S-, N-doped graphene quantum dots (GQDs) was synthesis by using citric acid as C source and thiourea as N, S source via facile hydrothermal synthesis route. Then, composite films of polyaniline-GQD (PANI–GQD) were prepared by in-situ electrochemical polymerisation of an aniline solution containing GQD. In the first part of the project, we demonstrate a new kind of Pt free counter electrode for dye-sensitized solar cells (DSSCs). PANI–GQDs nanocomposite, with the advantages of low cost and simple preparation, was prepared by in situ electrochemical polymerization of an aniline monomer in the presence of GQD and it shows good catalytic activity in promoting tri-iodide reduction. The fluorine doped tin oxide (FTO) coated glass was immersed into the solution of the aniline and GQD during the polymerization of PANI. The DSSC composed of the PANI–GQD nanocomposite electrode exhibits an energy conversion efficiency of 1.6 %. The presence of the synergistic effect of PANI and GQD led to the higher electrochemical catalytic activity of PANI–GQD nanocomposite than that of pristine PANI. In the second part, the different concentrations of GQD were utilized to improve the supercapacitor performances. The electrochemical performances of the composites were evaluated by cyclic voltammetry (CV). The results of electron microscope images showed that PANI were not only coated on the surface but also intercalated into GQD sheets. Application of the prepared samples has been evaluated as supercapacitor material in 0.5 M H 2 SO 4 solution using the CV technique. The specific capacitance of PANI–GQD composite films with redox peak was higher than that obtained for pure PANI films. In the third section, PANI-GQD/gold (PANI–GQD/Au) films were prepared by tow step electrochemical process. At the first step, mixture of aniline and GQD was refluxed then electopolymrization performed. At the second step gold’s nanoparticles were dispersed on the surface of PANI–GQD film from galvanostatic condition in the bath containing HAuCl 4 . Results indicated that gold nanoparticles were homogeneously dispersed on the surface of polyaniline film. The electro-oxidation of ascorbic acid is found to proceed more facile on PANI–GQD/Au electrode than on bare gold electrode. The irreversible oxidation current of ascorbic acid exhibits a linear dependence on the ascorbic acid concentration in the range of 1–5 mM. The nanocomposites were confirmed by FE-SEM, TEM, XRD, UV/vis and FT-IR analysis.