Ru@RuO2 Core‐Shell Nanorods: A Highly Active and Stable Bifunctional Catalyst for Oxygen Evolution and Hydrogen Evolution Reactions

Ru@RuO 2 core‐shell nanorods were successfully synthesized by heat‐treating Ru nanorods with air oxidation through an accurate control of the temperature and time. The structure, composition, dimension, and adsorption property of the core‐shell nanorods were well characterized with XRD and TEM. The catalytic activity and stability were electrochemically evaluated with a rotating disk electrode, a rotating ring‐disk electrode, and chronopotentiometric methods. The Ru@RuO 2 nanorods reveal excellent bifunctional catalytic activity and robust stability for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The overpotentials for OER and HER are 320 mV and 137 mV at the current density of 10 mA cm −2 , respectively. The catalytic activity of Ru@RuO 2 nanorods for OER is 6.5 times higher than that of the state‐of‐the‐art catalyst IrO 2 according to the catalytic current density measured at 1.60 V (versus RHE). The catalytic activity of Ru@RuO 2 nanorods for HER is comparable to 40% Pt/C by comparing the catalytic current densities at −0.2 V.