Dynamic Adsorption of Molybdate Promoted Self‐Optimization and Self‐Healing of NiFe/NiMo in Alkaline Water Electrolysis

The discovery of efficient and long-lasting dual-function catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is critical to the advancement of hydrogen synthesis from industrial electrolytic water. This study successfully synthesized the NiFe/NiMo heterojunction catalyst by preparing NiMoO₄ through a hydrothermal method, then calcination for reduction, and finally electrodepositing NiFe-LDH. The synthesized NiFe/NiMo catalyst demonstrates exceptional electrocatalytic activity, attaining a current density of 100 mA·cm^-2 with low overpotentials of 99 mV for HER and 233 mV for OER. Using NiFe/NiMo to form a two-electrode system, the system achieves a high current density of 100 mA·cm^-2 with an impressively low applied voltage of 1.707 V. The superior catalytic activity arises from the excellent HER-active NiMo nanopillars and OER-active NiFe-LDH nanosheets, as well as the HER self-optimization and OER self-healing mechanism of NiFe/NiMo catalyst under the influence of free MoO₄ ^2- in solution. Concretely speaking, MoO₄ ^2- plays dual roles in the bifunctional catalysis: i) During HER, it dynamically improves the catalytic activity of NiFe-LDH by adsorbing on the surface of NiFe-LDH; ii) In OER, it can inhibit the leaching of Fe on the electrode surface or promote the re-adsorption of Fe on the electrode surface, thus contributing to the recovery of activity.