Strengthening covalency on metal corrosion engineering NiFe-layered double hydroxide electrocatalysts with hard Lewis acid to achieve stable and efficient seawater splitting

Corrosion engineering constructs MoO 4 2− -intercalated NiFe-LDH electrocatalyst for stable and efficient seawater splitting. • MoO 4 2− intercalation enhances the M-O covalency. • The MoO 4 2− intercalation promotes the formation of high-valent Ni 3+ and Ni 4+ active species. • The hard Lewis acid MoO 4 2− has strong selectivity toward OH − , avoiding the competitiveness of Cl − in seawater. • The MoO 4 2− -intercalated NiFe-LDH electrocatalyst relies on the synergistic catalytic mechanism of AEM and LOM. Undesirable adverse reactions caused by chloride ions (Cl − ) and the corrosion of active sites are obstacles to the oxygen evolution reaction (OER) in seawater splitting. Herein, we design a molybdate anion (MoO 4 2− )-intercalated NiFe-layered double hydroxide (NiFe-LDH) electrocatalyst and demonstrate that the introduction of MoO 4 2− generates more abundant oxygen vacancies, enhances the M-O covalency, and accelerates the formation of nickel (III) ion (Ni 3+ ) and further oxidation to nickel (IV) ion (Ni 4+ ). Meanwhile, the hard Lewis acid MoO 4 2− exhibits strong selectivity toward OH − , avoiding the competitiveness and corrosiveness of Cl − in seawater. The intercalation of MoO 4 2− modulates the electronic structure of nickel (Ni) and iron (Fe) active sites, optimizing the adsorbate evolution mechanism (AEM) pathway. Simultaneously, moderate activation of lattice oxygen favors the lattice oxygen evolution mechanism (LOM) pathway, facilitating a delicate balance between the AEM and LOM. In a 1.0 M KOH + 0.5 M NaCl electrolyte, the catalyst shows an overpotential of only 224 mV at a current density of 50 mA cm −2 and can operate stably for 1500 h. This work provides a simple and effective method for preparing high-efficiency OER catalysts through corrosion strategies, which can be widely applied to seawater electrolysis. Molybdate anion(MoO 4 2− ) can inhibit the corrosive damage of chloride ions (Cl − ) on the surface of NiFe-LDH catalysts, inducing beneficial surface reconstruction of MoO 4 2− /NiFe-LDH to generate a large number of oxygen evolution active sites,significantly reducing the reaction overpotential, enabling the catalyst to exhibit ultra-long electrocatalytic durability exceeding 1500 h at a high current of 1000 mA cm −2 . Download: Download high-res image (277KB) Download: Download full-size image