A high Faraday efficiency NiMoO4 nanosheet arrays catalyst by adjusting the hydrophilicity for overall water splitting.

To obtain a highly active, stable and bind-free electrode based on transition metal compound for water splitting, we have synthesized nickel foam-supported 3D NiMoO4 nanosheet arrays modified with 0D Fe-doped-carbon-quantum-dots (Fe-CQDs/NiMoO4/NF). The structure characterizations indicated that 0D Fe-CQDs are evenly dispersed onto the NiMoO4 sheets of the arrays. The contact angle analysis confirmed that the surface hydrophilia of the arrays is improved after the 0D Fe-CQDs deposited 3D on the NiMoO4 sheets. Here, both activity and durability in electrochemical water splitting are significantly enhanced on the Fe-CQDs/NiMoO4/NF catalysts. At a current density of 10 mA cm-2, the resultant Fe-CQDs/NiMoO4/NF revealed an overpotential of only 117 mV with for hydrogen evolution reaction (HER) ，a relatively low overpotential of 336 mV toward the oxygen evolution reaction (OER) and faraday efficiency up to 99%. We attribute this performance to the unique 3D nanosheet array structure, the synergistic effect, and the optimal hydrophilia for gas evolution evolved from the electrode surface.