Electrocatalytic properties of electrodeposited black ruthenium in acidic and basic media for hydrogen production via water electrolysis

The study aims to determine the feasibility of using electrodeposited black ruthenium on gold-coated silver as a possible substitute electrode to platinum in industrial water electrolysis. Cyclic voltammetry and linear sweep voltammetry were employed to characterize the electrochemical behavior and compare the electrocatalytic properties of Ru black and Pt in acidic (0.5M H₂SO₄) and basic (0.5M NaOH) media. The results of cyclic voltammetry show that Ru black exhibits anodic corrosion/dissolution coupled with oxygen evolution in acidic and basic media consistent with its Pourbaix diagram. Hence, it cannot be used as an anode in water electrolysis. Ru black however is a promising cathode in both media with overpotential (~0.1V in acid and ~0.4V in alkaline), and exchange current density, i_o, in the order of 10^-3 comparable to that obtained for Pt. Stability tests in acidic and alkaline media reveal cracking in the Ru black electrode possibly due to hydrogen adsorption in the metal lattice inducing strain. More intense cracking observed in the stability test in acidic media is attributed to the presence of sulfur, a hydrogen recombination poison, resulting in more hydrogen to get absorbed into the metal lattice. Hence, despite excellent electrocatalytic properties of Ru black, it faces reliability issues in long term water electrolysis.