Three-Dimensional Heterostructured NiCoP@NiMn-Layered Double Hydroxide Arrays Supported on Ni Foam as a Bifunctional Electrocatalyst for Overall Water Splitting.

Herein, the rational design and preparation of three-dimensional heterostructured NiCoP@NiMn-layered double hydroxide arrays supported on Ni foam (NiCoP@NiMn LDH/NF) is reported as a new bifunctional water-splitting electrocatalyst with high performance. Prepared with facile hydrothermal reactions and phosphorization, the NiCoP@NiMn LDH/NF is simultaneously highly active toward oxygen evolution reaction (OER) (100, 300, and 600 mA cm-2 at overpotentials of 293, 315, and 327 mV, respectively) and hydrogen evolution reaction (HER) (100, 200, and 300 mA cm-2 at overpotentials of 116, 130, and 136 mV, respectively). Interestingly, with cell voltages of 1.519, 1.642, 1.671, and 1.687 V at 10, 100, 200, and 300 mA cm-2, respectively, for overall water splitting, this electrocatalyst achieves 95.2% faradaic efficiency for OER, suggesting a relatively high contribution of water splitting in the apparent current in spite of the existence of partial catalyst oxidation. The heterostructure arrays supported on Ni foam have some advantages, acting as a bifunctional water-splitting electrocatalyst: (1) heterostructured NCoP@NiMn LDH combines the intrinsic properties of individual NiCoP (excellent activity for HER) and NiMn LDH (high activity for OER) via the effective interface engineering between the two phases; (2) the NiCoP core material serves as a fast electron transfer channel to enhance the electrode's electrical conductivity; and (3) Ni foam with a three-dimensional-network structure as a support is beneficial to exposing more active sites and ensures efficient gas bubble release and electron/mass transfer.