The article reports the development of an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst, denoted as Co-NG, is highly active and robust in aqueous media with very low overpotentials (30 mV). The catalytically active sites are associated with the metal centers coordinated to nitrogen, suggesting a new approach to preparing efficient single-atom catalysts. The synthesis of Co-NG involves heat-treating graphene oxide (GO) and cobalt salts in a gaseous NH₃ atmosphere. Characterization techniques, including SEM, TEM, XPS, and EXAFS, confirm the atomic dispersion of cobalt in the nitrogen-doped graphene matrix. Electrochemical measurements show that Co-NG exhibits excellent HER activity, with a Faradaic efficiency of ~100% and a Tafel slope of 31 mV decade⁻¹. The catalyst's stability is also evaluated, showing excellent performance in both acidic and basic media. This work represents a promising candidate for replacing platinum in water splitting applications due to its low cost, high efficiency, and scalability.The article reports the development of an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst, denoted as Co-NG, is highly active and robust in aqueous media with very low overpotentials (30 mV). The catalytically active sites are associated with the metal centers coordinated to nitrogen, suggesting a new approach to preparing efficient single-atom catalysts. The synthesis of Co-NG involves heat-treating graphene oxide (GO) and cobalt salts in a gaseous NH₃ atmosphere. Characterization techniques, including SEM, TEM, XPS, and EXAFS, confirm the atomic dispersion of cobalt in the nitrogen-doped graphene matrix. Electrochemical measurements show that Co-NG exhibits excellent HER activity, with a Faradaic efficiency of ~100% and a Tafel slope of 31 mV decade⁻¹. The catalyst's stability is also evaluated, showing excellent performance in both acidic and basic media. This work represents a promising candidate for replacing platinum in water splitting applications due to its low cost, high efficiency, and scalability.