Ultrathin IrRu nanocages with tunable electronic reciprocity for highly efficient water splitting in acidic media

Abstract

The development of bifunctional electro-catalysts with high efficiency toward both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in acidic media still remains a challenge. Herein, we report a seed-mediated growth and etching method to fabricate ultrathin Ir_xRu_1−x cubic nanocages with precisely controlled atom accuracy of six atomic layers (∼1.21 nm) and well-defined {200} facets. Tunable electronic reciprocity is achieved through a precise control over the ratio of Ir and Ru, thus simultaneously optimizing the HER and OER performance. The optimal electronic reciprocity is acquired at x = 0.5, and the resultant Ir_0.5Ru_0.5 nanocages exhibit a significantly low overpotential of 18 mV and 219 mV at 10 mA cm_geo⁻² (η₁₀) for the HER and OER in acidic medium, with 22.8 and 18.7 times higher mass activity in comparison with Pt/C and RuO₂, respectively. Meanwhile, remarkable durability is pledged at x ≥ 0.5 for Ir_xRu_1−x due to the electrochemical formation of Ir_xRu_1−xO₂ as active and stable phases for both the HER and the OER. Consequently, a home-made overall water splitting electrolyzer with Ir_0.5Ru_0.5 nanocage electrodes can steadily operate and afford η₁₀ as low as 1.472 V and outperforms state-of-the-art electrolyzers.