Stabilizing single-atomic ruthenium by ferrous ion doped NiFe-LDH towards highly efficient and sustained water oxidation

Abstract

Single-atom catalysts (SAC) possesses the potentials of developing cost-effective water splitting devices; however, the active sites tend to form high valence state and dissolve into electrolyte at the anode during long-term oxidation process, leading to severe stability issue. Herein, we anchored single atomic Ru on Fe2+ ions doped NiFe layered double hydroxides, affording a strong electronic interaction between Ru and Fe2+, which lowered the oxidation state of Ru and meanwhile enhanced the Fe-O bond strength, thus resulting in significantly improved activity and stability of both the Ru sites and NiFe-LDH substrates. With 1.32 wt% Ru loading, the Ru/NiFe2+Fe-LDH catalyst showed a low overpotential of 194 mV at 10 mA / cm2 and a small Tafel slope of 36 mV / dec, which outperformed most of the Ru and NiFe based alkaline OER catalysts reported so far. In addition, the catalyst did not show obvious performance decay and dissolution after 100 h stability test at 100 mA / cm2, attributing to the strong electronic coupling between the single atomic Ru and the NiFe2+Fe-LDH, as evidenced by the X-ray absorption spectroscopy and density function theory calculation results that Fe2+ transferred 1.54 e- to Ru.