Iron doped cobalt fluoride derived from CoFe layered double hydroxide for efficient oxygen evolution reaction

Water splitting plays an important role in overcoming the intermittent problems for sustainable energy development, and an efficient non-noble catalyst is highly desired to catalyze the more sluggish half-reaction of oxygen evolution reaction (OER). Herein, we demonstrated the Fe-doped CoF2 as a novel and efficient catalyst for OER via facile structural transformation derived from the CoFe layered double hydroxide. The crystal structure and surface chemical state analysis indicated the successful structural transformation from CoFe layered double hydroxide to the bulk crystal of CoF2 doped by Fe. The obtained Fe-CoF2 nanoflakes largely improved the utilization of active sites and effectively promoted mass transfer. The Fe-CoF2-300 showed a low overpotential of 230 mV to achieve the current density of 10 mA cm−2 when loaded on an inert glass carbon electrode, which is about 60 mV less than that of the pristine CoFe layered double hydroxide catalyst. It also exhibited a small Tafel slope of 41.9 mV dec-1 and super catalytic stability. High valence state change from the M−F bond to the M−O bond driven by the OER process was indicated after the long-term stability test indicating the facile active phase formation. This works provides an effective doping strategy to design novel catalysts for decreasing the overpotential and accelerating the kinetics of OER.