Elevating the d-Band Center of Ni3S2 Nanosheets by Fe Incorporation to Boost the Oxygen Evolution Reaction.

ABSTRACT

Many attempts have been made to enhance the relatively poor electrochemical activity of Ni3S2 for the oxygen evolution reaction (OER) by elevating the d-band center. Unfortunately, only limited success has been encountered thus far. Owning to the lower electronegativity and one less 3d electron relative to Ni, Fe shows great potentials in upshifting the overall d-band center of Ni3S2 when incorporating into its crystal structures. Herein, to enhance the intrinsic activity by elevating the d-band center, Ni3S2 nanosheets incorporated with suitable Fe content have been fabricated by a facile one-step solvothermal method. The obtained Fe-incorporated Ni3S2 catalyst exhibits an outstanding OER performance in alkaline media, only requiring 244 mV overpotential (with a reduction of 210 mV compared to Ni3S2) at 50 mA cm-2 in 1 M KOH and without obvious degradation after sustaining for a 60 h test at a voltage above 1.5 V. Ultraviolet photoemission spectroscopy and density functional theory calculations consistently demonstrate that the superior performance of Fe-incorporated Ni3S2 is attributed to the upshift of the d-band center on neutralizing the electron densities of Ni, which optimize greatly the adsorption energy of the intermediate (OOH*) in the rate-determining Volmer step.