Ruthenium (IV) oxide layer coated nickel-doped manganese oxide nanorods for electrocatalytic oxygen evolution in acid

Abstract

Efficient electrocatalysts for acidic oxygen evolution reaction (OER) are essential to the development of proton-exchange water electrolyzers. Construction of core-shell heterostructures is a viable route to design electrocatalysts that are highly active and stable. Here, RuO₂ coated Ni-doped MnO₂ nanorods (NiMnO₂@RuO₂) are synthesized by immersing surfactant-free NiMnO₂ nanorods in RuCl₃ aqueous solution, then annealed at 400℃ for 2 h. The NiMnO₂@RuO₂-15 (NiMnO₂ nanorods dispersed in RuCl₃ aqueous solution (pH = 4.9) in air for 15 h) are the most active electrocatalysts in 0.1 M H₂SO₄, and only 165 mV overpotentials are required to reach the 10 mA cm^-2 OER current densities. At 1.38 V, the mass activity of NiMnO₂@RuO₂-15/CP reaches 1.36 A mg_Ru^-1. The increased number of electrochemically active Ru sites and enhanced intrinsic activity could account for the high activity of the NiMnO₂@RuO₂-15. Kinetic analyses and characterizations indicate that the electron interaction between the core and shell layer tunes the adsorption energy of the OER intermediates and accelerates the OER kinetics, and the lattice oxygen oxidation mechanism is involved in OER. The NiMnO₂@RuO₂ are also stable towards the long-term OER in acid.