ZIF-L(Co)-derived NiCoFe LDH@ZIF-67 sheet-array for efficient and robust electrocatalytic seawater splitting

The design of efficient composite catalysts by combining layered double hydroxide (LDH) and metal-organic framework (MOF) is of great importance for green hydrogen energy production in seawater . Herein, a Zeolitic Imidazolate Framework (ZIF)-L(Co) derived strategy was used for the initial formation of NiCo LDH@ZIF-67 sheet-array (NiCo ZSA) and subsequent formation of NiCoFe LDH@ZIF-67 sheet-array (NiCoFe ZSA) catalysts on Cu foam (CF). Morphology inheritance process enabled the construction of hierarchical composite catalysts by forming crosslinked LDH nanoflakes on ZIF sheets, which provided more exposed active sites for electrocatalytic reaction . A series of NiCoFe ZSA trimetallic catalysts were obtained by tuning the reaction time of Fe-doping in NiCo ZSA. The optimal NiCoFe ZSA-30 catalyst exhibited superior electrocatalytic performance in the alkaline simulated seawater , the electrode required overpotentials of only 326 and 321 mV at a large current density of 500 mA cm −2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). NiCoFe ZSA-30-based two-electrode system was used for overall seawater splitting, 97.0 % and 93.1 % of the initial voltage maintained for 50 hours of continuous electrolysis at 500 mA cm −2 in alkaline simulated and natural seawater. Multi-metallic synergy effect among Ni, Co, and Fe species simultaneously reduced interfacial charge-transfer barriers and improved mass transport characteristics, whereas the coordinated effects of Fe incorporation and SO 4 2− intercalation conferred exceptional corrosion resistance in chloride-rich electrolytes. This study provides efficient and stable catalysts to achieve direct alkaline seawater splitting for sustainable and energy efficient hydrogen production .