Ruthenium disulfide is a transition metal sulfide with metallic or semi-metallic conductivity and high chemical and thermal stability. In nanoparticle form, RuS₂ exhibits enhanced surface reactivity and excellent electrocatalytic performance, particularly for hydrogen evolution and oxygen reduction reactions. These properties make RuS₂ nanoparticles attractive as noble-metal-efficient catalysts in energy conversion technologies, including water electrolysis, fuel cells, and electrochemical sensing.