Highly Active NiO-Ni(OH)₂ -Cr₂ O₃ /Ni Hydrogen Evolution Electrocatalyst through Synergistic Reaction Kinetics

High activity catalysts for hydrogen evolution reaction (HER) play a key role in converting renewable electricity to storable hydrogen fuel. Great effort has been devoted to the search for noble metal free catalysts to make electrolysis viable for practical applications. Here, a non-precious metal oxide/metal catalyst with high intrinsic activity comparable to Pt/C was reported. The electrocatalyst consisting of NiO, Ni(OH)₂ , Cr₂ O₃ , and Ni metal exhibits a low overpotential of 27, 103, and 153 mV at current densities of 10, 100, and 200 mA cm^-2 , respectively, in a 1.0 m NaOH electrolyte. The activity is much higher than that of NiO_x /Ni or Cr₂ O₃ alone, showing the synergistic effect of NiO_x /Ni and Cr₂ O₃ on catalyzing HER. Density functional theory calculations shows that NiO and Cr₂ O₃ on Ni surface lower the disassociation energy barrier for breaking H-OH bond, while Ni(OH)₂ and Cr₂ O₃ create preferred sites on Ni surface with near-zero H* adsorption free energy to promote H* to gaseous H₂ evolution. These synergistic effects of multiple-oxides/metal composition enhance the disassociation of H-OH and the evolution of H* to gaseous H₂ , thus achieving high activity and demonstrating a promising composition design for noble metal free catalyst.