Template-free synthesis of pure and Co-doped ZrO2 tetragonal structured nanoparticles was achieved by the hydrothermal method and their photocatalytic, photoelectrocatalytic, and electrochemical energy storage supercapacitive properties were investigated for the first time. XRD revealed tetragonal crystal structure, while BET surface analysis suggested that Co-doped ZrO2 has higher surface area (186.4 m(2)g(-1)) than that of the undoped sample (99.5 m(2)g(-1)). The band gap value was reduced from 4.95 to 2.12 eV due to incorporation of cobalt. Under visible-light illumination, photocatalytic and photoelectrocatalytic activities for methyl orange (MO) dye degradation were evaluated. The working electrodes have been prepared with 85 wt% active material (pure and doped ZrO2), 10 wt% active carbon black, and 5 wt% polyvinylidene difluoride (PVDF) in order to perform the supercapacitive properties. The Co-doped ZrO2 material exhibited 93.7% and 27.4% MO dye degradation within 100 min with the highest specific capacitance value of 2151.2 Fg(-1). (C) 2019 Elsevier Ltd. All rights reserved.