Ultrasonic spray pyrolysis synthesis of nano-cluster ruthenium on molybdenum dioxide for hydrogen evolution reaction

• Ru-doped MoO 2 was prepared by ultrasonic spray pyrolysis in one step. • High-dispersed ruthenium had strong interactions with MoO 2 . • A high concentration of ruthenium on the MoO 2 surface enhanced hydrogen evolution activity. • Ru-MoO 2 showed excellent mass activity in all pH range. Platinum (Pt)-based catalyst is a state-of-the-art catalyst for hydrogen evolution reaction (HER) of electrochemical water splitting. Nevertheless, to minimize the overall water electrolysis cost, a new catalyst must be developed. Ruthenium (Ru)-based catalyst has recently been found to be an efficient HER catalyst in all pH ranges of electrolytes. However, they demonstrated lower HER activity than Pt-based catalysts. Hence, to maximize the electrocatalytic activity, a highly dispersed Ru-based catalyst should be studied while maintaining a high-loading amount. This study prepares a high-dispersed Ru catalyst using the ultrasonic spray pyrolysis (USP) process on a molybdenum dioxide (MoO 2 ) support. The USP process enabled the dispersion of Ru on MoO 2 with high-loading (9 wt%) and dispersion. The high dispersion of Ru and the strong interaction between Ru and MoO 2 improved the HER activity.