This work presents a comparative electrochemical and spectroelectrochemical study of composites consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) synthesized in different electrolyte solutions. The electrochemical behavior of PEDOT/GO composites were studied in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) as well as in conventional organic (acetonitrile) and aqueous electrolytes by cyclic voltammetry and electrochemical impedance spectroscopy. Additionally, we applied in situ Attenuated Total Reflection Fourier Transformed Infrared (ATR-FTIR) spectroelectrochemistry using a Kretschmann geometry cell to study the composite fabrication during potentiodynamic electropolymerization, and to study the electronic properties and charge carrier formation during p-doping. According to in situ ATR-FTIR analysis, the doping induced bands from charge carrier formation begin to grow at lower potentials for the composite film and the electronic absorptions indicate formation of only one type of charge carrier in the composite made and characterized in ionic liquid. The optical properties during doping were determined by in situ UV-Vis spectroelectrochemistry. The composite film fabricated in water has its absorbance maximum at slightly higher wavelengths, and the appearance of the film is changed from well-known light blue color of PEDOT to greyish. (C) 2019 Elsevier Ltd. All rights reserved.