Ultrafine Ruthenium Oxide Nanoparticles Supported on Molybdenum Oxide Nanosheets as Highly Efficient Electrocatalyst for Hydrogen Evolution in Acidic Medium

Engineering of efficient, robust and inexpensive Pt‐free catalysts for the hydrogen evolution reaction has drawn great attention, and there is a rapidly growing demand for electrochemical water‐splitting reactions. Here, we report, for the first time, synthesis of ruthenium oxide nanoparticles supported on molybdenum oxide nanosheets (MoO 3 @RuO 2 ). This composite catalyst was prepared sonochemically, followed by calcination of the product in air at 400 °C for one hour. The as‐synthesized MoO 3 @RuO 2 composite catalyst was used to explore the electro‐catalytic hydrogen evolution reaction in acidic medium. Notably, compared to MoO 3 or RuO 2 , the composite exhibited high exchange current density of 0.57 mA cm −2 , and a current density of 10 mA cm −2 was achieved at low overpotential of 110 mV in 0.5 M H 2 SO 4 . The Tafel slope of the MoO 3 @RuO 2 catalyst was 62 mV dec −1 and it showed excellent stability. This remarkable performance can be attributed to the synergetic effect generated by the strong interaction between MoO 3 nanosheets and RuO 2 nanoparticles, which resulted in enhanced long‐term stability as well.