Cerium oxide (CeO2-delta) ultrafine nanoparticles, with the lower (CeO2-delta-HT) and higher (CeO2-delta-SS) fraction of oxygen vacancies, were used as anchoring sites for the polymerization of aniline in acidic medium. As a result, polyaniline-emeraldine salt (PANI-ES)-based composites (PANI-ES@CeO2-delta-HT and PANI-ES@CeO2-delta-SS) were obtained. The interaction between CeO2-delta and PANI was examined by FTIR and Raman spectroscopy. The PANI polymerization is initiated via electrostatic interaction of anilinium cation and Cl- ions (adsorbed at the protonated hydroxyl groups of CeO2-delta), and proceeds with hydrogen and nitrogen interaction with oxide nanoparticles. Tailoring the oxygen vacancy population of oxide offers the possibility to control the type of PANI-cerium oxide interaction, and consequently structural, electrical, thermal, electronic and charge storage properties of composite. A high capacitance of synthesized materials, reaching similar to 294 F g(-1) (PANI-ES), similar to 299 F g(-1) (PANI-ES@CeO2-delta-HT) and similar to 314 F g(-1) (PANI-ES@CeO2-delta-SS), was measured in 1 M HCl, at a common scan rate of 20mV s(-1). The high adhesion of PANI with cerium oxide prevents the oxide from its slow dissolution in 1 MHCl thus providing the stability of this composite in an acidic solution. The rate of electrochemical oxidation of emeraldine salt into pernigraniline was also found to depend on CeO2-delta characteristics. (c) 2019 Elsevier Ltd. All rights reserved.