Ir Cluster-Decorated Carbon Composite as Bifunctional Electrocatalysts for Acidic Stable Overall Water Splitting

In this paper, the bifunctional Ir cluster-decorated carbon Composite (Ir/C-1) electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are synthesized through simple in-situ growth of bimetallic Zn-Ir-MOF, followed by Zn reduction and evaporation for creating pore structure and uniform particle distribution. The prepared catalyst of Ir/C-1 with Ir cluster (d = 3 ± 0.1 nm) highly dispersed and closely attached to pore carbon through Ir–O–C bonds shows both excellent OER and HER performance. At a current density of 10 mA cm−2, the catalyst shows overpotentials of only 50.4 mV for HER and 359 mV for OER in 0.5 M H2SO4, respectively, which are better than commercial Ir/C and Pt/C catalysts. Density functional theory (DFT) calculations further revealed that the exposure of Ir (110) in Ir/C-1 can facilitate the thermodynamic process of HER and OER. This paper also gives a detailed discussion about the enhancement mechanism. To validate the catalyst, a single electrolysis cell is assembled using the prepared Ir/C-1 catalyst as both the anode and cathode catalysts. The result shows that the cell only needs a cell voltage of 1.653 V to obtain a current density of 10 mA cm−2, which is better than commercial Ir/C and Pt/C catalysts.