Blocking Effect Retards Electron Release from Asymmetric Active Units for Selective Seawater Oxidation.

Abstract

During seawater electrolysis, chloride ion (Cl^-) adsorption at the anode leads to an inevitable competitive chloride oxidation reaction (ClOR) with the oxygen evolution reaction (OER), compromising the long-term stability of the electrolysis process. Furthermore, Ni-based OER electrocatalysts are challenged by activity degradation due to the overoxidation of Ni³⁺. In response, we present a design of oxygen-vacancy-regulated asymmetric Nb-O-Ni bonds aimed at selective seawater oxidation. The experimental and in situ characterization results indicate that the blocking effect of oxygen vacancies effectively alleviates the electron release of Ni³⁺ and the electron enrichment of Nb⁵⁺ on asymmetric Nb-O-Ni bonds, achieving a stable and selective OER in alkaline seawater. Density functional theory (DFT) calculations reveal that oxygen vacancies in Nb-O-Ni bonds optimize the adsorption strength of reaction intermediates and break up the scaling relationship between *OH and *OOH intermediates. The constructed anion exchange membrane electrolysis cell achieves a cost efficiency of $1.07 per GGE (gasoline gallon equivalent) for H₂ production at a current density of 1000 mA cm^-2, maintaining operational stability for 100 h at 500 mA cm^-2.