Ir nanodots decorated Ni3Fe nanoparticles for boosting electrocatalytic water splitting

Developing low-cost and high-performance electrocatalysts for water splitting is crucial for advancing the hydrogen production. However, the large-scale practical application is highly dependent on the use of precious catalysts (such as IrO2 and Pt/C). Herein, a composite of Ir nanodots (7.7 wt%) decorated Ni3Fe alloy on reduced graphene oxide (Ir/Ni3Fe/rGO) is prepared via an impregnation-reduction method as a bifunctional electrocatalyst for overall water splitting. The low-content decoration enables the composite to exhibit attractive electrocatlytic performances: requiring overpotentials of 254 and 36 mV at a current density of 10 mA cm−2 for the oxygen and hydrogen evolution reactions (OER and HER) in 1.0 M KOH solution, respectively, which surpass those of Ni3Fe/rGO (280 and 264 mV) and Ir/rGO (340 and 150 mV). In addition, the electrocatalyst-assembled Ir/Ni3Fe/rGO||Ir/Ni3Fe/rGO electrolyzer affords a decent cell voltage of 1.570 V at a current density of 10 mA cm−2 for overall water splitting, which outperforms those of Ni3Fe/rGO||Ni3Fe/rGO (1.730 V), Ir/rGO||Ir/rGO (1.790 V), and commercial IrO2||Pt/C (1.574 V). Furthermore, X-ray photoelectron spectroscopy (XPS) result reveals the strong interfacial interaction between Ir and Ni3Fe species, density functional theory (DFT) calculations reveal that Ir species favor water dissociation and optimize the H* adsorption energy for HER, and reduce OOH* energy for OER; all of which give rise to the observed enhancement. The results can provide an effective strategy for designing and preparing low-cost and promising electrocatalysts for water splitting.