Promoting mechanism of the Ru-integration effect in RuCo bimetallic nanoparticles for enhancing water splitting performance

The development of electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is crucial for sustainable energy and environmental initiatives. This work establishes an atomically-dispersed Ru-based model to investigate the promoting mechanism by the Ru-Integration effect in RuCo bimetallic nanoparticles supported on nitrogen-doped carbon (RuCo@NC). Specially, the Ru content in RuCo@NC plays a vital role for both HER and OER. The optimized catalyst shows an outstanding performance, requiring only 217 and 97 mV overpotential to reach a current density of 10 mA·cm⁻² for OER and HER respectively in alkaline conditions. Combined with advanced characterizations such as spherical aberration-corrected scanning transmission electron microscopy, X-ray absorption spectroscopy, in-situ Raman spectroscopy, and density functional theory calculations, it is found that Ru plays multiple crucial roles: (1) Ru restricts the growth of large Co NPs, while the small-sized Co NPs facilitate the formation of carbon nanotubes, which significantly enhances the mass/electron transfer; (2) Ru not only tunes the surface properties of Co but also acts as an active site for HER. As a result, when using RuCo@NC as an overall water splitting catalyst, it only needs a potential of 1.62 V to reach a current density of 100 mA·cm⁻². This work offers valuable insights into designing Ru-based electrocatalysts for water splitting.