Cationic defect engineering induces LOM-enhanced electrocatalysts derived from in situ semi-transformed NiFe-LDH/MOF heterostructure for efficient overall water-splitting

Unraveling the lattice oxygen mechanism (LOM) pathway and its association with inherent electrocatalytic performance is key to designing electrocatalyst for water-splitting but unfortunately remains elusive. Herein, a 3D nanoflower-like NiFe-LDH/MOF heterostructured electrocatalyst based on MXene is successfully prepared by an in situ semi-transformation (ISST) strategy. Chemical probe tests and pH-dependent tests indicate that the introduction of defects in the catalysts reduce the energy of the metal-oxygen bond and promote the release of lattice oxygen during the OER process, further enhancing the LOM pathway. Density Functional Theory (DFT) calculations also demonstrated that electronic coupling at heterogeneous interfaces and defect engineering optimised the adsorption process of the reaction intermediates and markedly improved the intrinsic catalytic activity. As expected, the catalysts exhibited good electrochemical performance, with HER and OER requiring only 143 mV and 176 mV. In addition, the overall water-splitting tests indicate that merely 1.55 V of cell voltage is needed for the catalyst to attain a current density of 10 mA cm −2 . Excellent stability is also observed at high current densities, demonstrating its potential to be used as a bifunctional catalyst for large-scale industrialized applications. • Unique heterogeneous structure synthesised by in situ semi-transformation. • Introduction of cationic defects to enhance the lattice oxygen mechanism (LOM) pathway. • A voltage of ∼1.55 V drives 10 mA cm −2 current in the two-electrode electrolyzer. • The mechanism of electrocatalyst is revealed by density functional theory (DFT).