An amorphous ultrathin iridium/carbon catalyst realizing efficient electrochemical hydrogen evolution.

An amorphous 1.1 nm Ir/C catalyst exhibits ultralow overpotentials of 10 and 64 mV for the hydrogen evolution reaction at current densities of 10 and 100 mA cm -2 , together with 117 A mg -1 mass activity and outstanding long-term durability, superior to those of the commercial Pt/C catalyst.