Ultrathin nickel-iron layered double hydroxide nanosheets intercalated with molybdate anions for electrocatalytic water oxidation

There have been growing efforts to search for active, robust and cost-effective electrocatalysts for the oxygen evolution reaction (OER). Among the different candidates, Ni-Fe layered double hydroxides (LDHs) hold great promise due to their high activity closely approaching or even outperforming that of the precious metal benchmark in alkaline media. Here, we show that their activity can be further promoted when forming ultrathin LDH nanosheets intercalated with molybdate ions via an exfoliation-free hydrothermal method. In 1 M KOH, these nanosheets exhibit about 3-fold higher OER current density than regular NiFe LDH nanosheets, which was believed to be mostly contributed by their higher available density of electrochemically active sites associated with the ultrathin thickness. The great activity is also accompanied by remarkable durability at different current density levels. Finally, we demonstrate that these ultrathin nanosheets can also be directly grown on Ni foam for achieving significant current densities.