Ruthenium/nitrogen-doped carbon as an electrocatalyst for efficient hydrogen evolution in alkaline solution

For all electrocatalysts (even Pt), the kinetics of the hydrogen evolution reaction (HER) in alkaline environments are more sluggish by a factor of two to three compared to those in acidic solutions. Here, we demonstrated the preparation of a novel ruthenium/nitrogen-doped carbon (Ru/NC) electrocatalyst supported by graphite foam, in which abundant, singly dispersed Ru atoms were chelated to a nitrogen-doped carbon matrix. In a 1 M KOH aqueous solution, the resultant Ru/NC electrocatalyst exhibited excellent electrocatalytic HER activity with an extremely low overpotential of only 21 mV at 10 mA cm^-2 and an excellent mass current density as high as 8 A mg_Ru^-1 at 100 mV, which is superior to the values for reported electrocatalysts (overpotentials of >50 mV at 10 mA cm^-2), even Pt catalysts (overpotential of ∼36 mV at 10 mA cm^-2). Importantly, the inherent turnover frequency (TOF) value (per Ru atom) of the Ru/NC electrocatalyst reaches 4.55 s^-1, which is 3.2 times higher than that of the Pt catalyst (1.41 s^-1). Electrochemical analyses and structural characterization revealed that atomically dispersed Ru is responsible for the outstanding HER activity of the Ru/NC electrocatalyst because of a substantially accelerated Volmer step. The outstanding HER performance gives the Ru/NC electrocatalyst promising potential for practical hydrogen production applications.