Electrochemically assisted synthesis of ultra-small Ru@IrOx core-shell nanoparticles for water splitting electro-catalysis

Abstract Carbon-free use of hydrogen as a clean fuel and a viable energy storage medium has been impeded by the efficiency of water electrolysis, which in turn, is limited by the bottleneck anodic oxygen evolution reaction (OER). The discovery of potentially efficient catalysts for OER is a key factor to facilitate the overall kinetics of water splitting, in which, noble metals such as Ru and Ir are still the conventional benchmarks. However, besides the high cost, such catalysts are also suffered from rapid performance degradation under OER conditions, particularly for Ru. In this work, Ru@IrOx core-shell nanoparticles (NPs) are successfully obtained through a wet chemical synthesis with the assistance of electro-oxidation. The NPs possess an ultra-small size of about 3.4 nm, achieving high specific OER activities of 51.99 μA/cm2oxide and 3.44 μA/cm2oxide as well as mass activities of 44.85 A/goxide and 3.03 A/goxide at overpotential of 250 mV (vs. RHE) in 0.1 M HClO4 and in 0.1 M KOH respectively. Furthermore, as-synthesized Ru@IrOx core-shell NPs are also proven to have excellent catalytic stability in both electrolytes, exhibiting great potential for application in both acidic and alkaline water electrolyzers.