Chloride-Mediated Electron Buffering on Ni-Fe Anodes for Ampere-Level Alkaline Seawater Electrolysis

Abstract

In water electrolysis, the long-term stability of anodes is compromised by their degradation under oxidative conditions. This issue becomes more pronounced in seawater electrolysis, where the natural chloride ion (Cl⁻) induces the chlorine evolution reaction (ClER) to produce corrosive byproducts. Herein, a series of small organic molecules (SOMs), featuring an aromatic carbon ring with para-positioned carbonyl groups, are integrated with the conventional nickel-iron (Ni-Fe) based anode. This integration triggers a unique electron buffering effect to address anode degradation in natural seawater-based electrolytes. It is found that preferential adsorption of Cl⁻ onto SOMs prevents its direct interaction with metal active sites. Furthermore, SOM-Cl serving as an electron buffering group significantly reduces the dissolution of Fe sites under the highly oxidative environment. As a result, the SOM-Cl-engineered anode enhances oxygen evolution activity by ≈1.7 times in seawater compared to pure water. In addition, the rationally designed anode works stably for over 200 h at a high current density of 1.3 A cm⁻² in an alkaline seawater electrolyzer (ASE).