Shape-tunable PtAg nanocatalysts including PtAg nanoflowers (NFs) and PtAg nanowires (NWs) are prepared by a facile hydrothermal reduction method, via adjusting the precursor ratio of Pt/Ag and subsequent UV-irradiation. Physicochemical characterizations reveal that the as-prepared catalysts have a porous structure, which forms from the conversion of AgCl to Ag nanoparticles. These features favor both oxygen mass transfer and accessibility of active sites. The as-prepared Pt1Ag4 NWs exhibit superior catalytic performances for ORR. The mass activity of Pt1Ag4 NWs is 11.4 times higher than that of 20% Pt/C. More important, the electrochemically active surface area (ECSA) of Pt1Ag4 NWs is 2.5 times larger than that of commercial Pt/C. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.