Engineered Mo-O-Fe active centers for Efficient and Stable Overall Water Splitting along the Lattice-Oxygen Mechanism

The covalency of the metal-oxygen (M-O) bond is significantly enhanced in the transition metal sites with high oxidation states, thereby enabling the lattice oxygen-mediated mechanism (LOM) to break the traditional linear scaling limitations of the oxygen evolution reaction (OER). Here, an innovative MoO 2 surface is designed to adjust the covalency of Fe-O bond in NiFe layered double hydroxide (NiFe-LDH), which results in the formation of Fe-O-Mo bridge with high valence Fe species for OER along the LOM. The MoO 2 -modified NiFe-LDH anchored on nickel foam, shows a 3D nanoflower-like heterostructure of interwoven porous nanosheets, which exposes abundant active sites, boosts charge transfer, and modulates the reaction microenvironment via heterojunction and confinement effects. This designed architecture shows excellent bifunctional catalytic activity, manifested by low overpotentials for HER (131 mV) and OER (226 mV) at 10 mA cm -2 , respectively. The overall water electrolyzer verifies the device-level application potential assembled with MoO 2 /NiFe-LDH@NF as both cathode and anode, and achieves a low cell voltage of 1.650 V at 0.5 A cm -2 and stable operation for over 700 hours.