A High Faraday Efficiency NiMoO4 Nanosheet Array Catalyst by Adjusting the Hydrophilicity for Overall Water Splitting.

To obtain a highly active, stable, and binder-free electrode based on transition-metal compounds for water splitting, nickel foam-supported 3D NiMoO4 nanosheet arrays modified with 0D Fe-doped carbon quantum dots (Fe-CQDs/NiMoO4 /NF) are synthesized. 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 are deposited 3D on the NiMoO4 sheets. Here, both the activity and durability in electrochemical water splitting are significantly enhanced with 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 for the hydrogen evolution reaction (HER), a relatively low overpotential of 336 mV toward the oxygen evolution reaction (OER), and a Faraday efficiency of up to 99 %. This performance can be attributed to the unique 3D nanosheet array structure, the synergistic effect, and the optimal hydrophilia for gas evolution evolved from the electrode surface.