Superior water splitting by a hierarchical nickel-ruthenium/ruthenium-oxide electrocatalyst

Water splitting electrocatalysts are essential for realizing the green hydrogen energy vision. Here, we demonstrate that a novel hierarchical electrocatalyst comprising nickel foam coated with electrodeposited nickel-ruthenium alloy and ruthenium oxide (Ni foam/NiRu-RuO₂) exhibits, to the best of our knowledge, the most efficient water splitting performance in acidic conditions. The NiRu-RuO₂ electrocatalyst accomplished an extremely low oxygen evolution reaction (OER) overpotential of 170 mV at 10 mA cm⁻², low resistance, and chemical stability. The ruthenium-nickel composite also displayed good hydrogen evolution reaction (HER) properties, specifically an overpotential of 105 mV at 10 mA cm⁻². The superior catalytic properties of the Ni foam/NiRu-RuO₂ assembly are ascribed to the hierarchical micro- and nano-porous structure, furnishing high surface area and abundant redox sites, and the presence of NiRu alloy accounting for enhanced conductivity. A complete cell consisting of two Ni foam/NiRu-RuO₂ composite electrodes facilitated OWS at an extremely low cell voltage of 1.665 V at 10 mA cm⁻².