Atomically dispersed iridium catalysts for multifunctional electrocatalysis

Development of high-performance multifunctional electrocatalysts is of great concern for renewable energy systems. Here, atomically dispersed iridium embedded into nitrogen-doped graphene electrocatalyst (Ir@NG-750) is synthesized through simply annealing method. The atomic Ir@NG-750 catalyst exhibits excellent electrocatalytic performance for oxygen reduction reaction (ORR) in both acidic and alkaline media with half-wave potential of 0.77 V and 0.865 V, respectively, together with good durability, a four-electron pathway, and excellent resistance to carbon monoxide poisoning. It also shows outstanding electrochemical performance for hydrogen evolution reaction (HER), providing low overpotentials of 114 mV and 25 mV at 10 mA•cm−2 in 0.1 M KOH and 0.5 M H2SO4, respectively. Moreover, it displays superior catalytic performance for oxygen evolution reaction with low overpotentials of 273 mV, 340 mV, and 371 mV at 10 mA•cm−2, in 1.0 M KOH, 0.1 M KOH and 0.5 M H2SO4, respectively. Due to excellent trifunctional properties, it can deliver overall water splitting current density of 10 mA•cm−2 at cell voltage of 1.7 V. In addition, the Ir@NG-750-based Zn-air battery exhibits a peak power density of 56.8 mW cm-2 at the voltage of 0.62 V. DFT calculations reveal that IrN4-G center is the active site for these reactions.