Engineering ultrafine Ir nanocrystals for electrochemical hydrogen evolution with highly superior mass activity

Highly active and durable noble metal-based catalysts for electrochemical hydrogen evolution are crucial for clean and renewable energy production, however, low abundance and high price hinder their development at industrial scale. Herein, we synthesized carbon-supported ultrafine iridium nanoparticles (Ir NPs/C) catalyst via solvothermal method which achieved ultralow overpotentials of 13 and 57 mV at the current density of 10 and 100 mA cm-2 for hydrogen evolution reaction (HER) in acidic media, respectively. The prepared Ir NPs/C catalyst also exhibited ultrahigh mass activity of 44.5 A mg- 1 at the overpotential of 40 mV and outstanding long-term stability in HER performance for 12 h, remarkably superior to state-of-the-art commercial Pt/C catalyst (3.3 A mg -1, fast decay) and commercial Ir/C catalyst (1.2 A mg -1). Furthermore, it possessed activities toward oxygen evolution reaction (OER) and overall water splitting. This work demonstrates evenly dispersed fine Ir NPs/C catalyst can facilitate highly efficient HER and provides inspiration for rational design of advanced electrocatalysts.