Pt nanostructures are intensively studied for many environmental and energy applications. Their synthesis normally involves capping agents/organic species or the assistance of templates/substrates, making the preparation process complicated. Therefore, it is still challenging to obtain Pt nanostructures with clean surface through a one-step surfactant-free method. We report herein the preparation of 3 D Pt nanodendrites with clean surface by a facile inorganic species assisted strategy. The possible specific adsorption of iron and nitrate ions would assist the growth of this 3 D Pt nanostructure. Thanks to its unique 3 D morphology composed of interconnected 1 D Pt nanorods/wires, the unsupported 3 D Pt nanodendrites exhibit higher stability and activity than commercial carbon black supported Pt nanoparticles and Pt black electrocatalysts for the oxygen reduction reaction and oxidation of small fuel molecules.