An ultrafine ruthenium nanocrystal with extremely high activity for the hydrogen evolution reaction in both acidic and alkaline media

An ultrafine ruthenium nanocrystal (RuNC) was fabricated via thermal annealing tris(2,2′-bipyridine)ruthenium dichloride with cyanuric acid. The as-obtained RuNC features a small diameter of ∼2 nm and high crystallinity. As an electrocatalyst for the hydrogen evolution reaction, the ultrafine RuNC exhibited remarkable performance in both acidic and alkaline media.