Interfacial Electrostatic Engineering for Chlorine Ions Blocking Toward Long-Lasting Alkaline Seawater Oxidation.

Abstract

The existence of Cl^- in seawater electrolysis weakens the selectivity of the oxygen evolution reaction (OER) via the chlorine evolution reaction (CER) and causes material failure by chlorine pitting. Introducing anion layers not only repels the transition of Cl^- without retarding the diffusion of oxygen-containing anions but also can be generated in situ on the outer surface. Here, a hierarchical catalyst consisting of a MnO₂ layer formed on a Ni foam substrate covered uniformly by a nickel-iron layered double hydroxide (NiFe-LDH) active layer is developed through interfacial electrostatic engineering. It was found that the introduced Lewis acid layer (MnO₂) can spontaneously generate OH^- groups on the outer surface in situ to repel Cl^- by electrostatic repulsion force. Meanwhile, Ni-active sites anchored inside the MnO₂ matrix can improve the low activity of MnO₂. The multilayer NiFe-LDH@MnO₂/NF anode can operate steadily at the current density of 100 mA cm^-2 at 70 °C for 100 h and maintain 97.9% OER selectivity. Furthermore, the OER overpotential was reduced by 136 mV, superior to the state-of-the-art commercial Ni mesh in industrial environments, especially the device can be powered by wind energy. The work offers an efficient strategy for designing high-performance seawater electrolysis with low cost and high stability.