Concerning the stability of seawater electrolysis: a corrosion mechanism study of halide on Ni-based anode

Abstract

The corrosive anions (e.g., Cl ⁻) have been recognized as the origins to cause severe corrosion of anode during seawater electrolysis, while in experiments it is found that natural seawater (~0.41 M Cl ⁻) is usually more corrosive than simulated seawater (~0.5 M Cl ⁻). Here we elucidate that besides Cl ⁻, Br ⁻ in seawater is even more harmful to Ni-based anodes because of the inferior corrosion resistance and faster corrosion kinetics in bromide than in chloride. Experimental and simulated results reveal that Cl ⁻ corrodes locally to form narrow-deep pits while Br ⁻ etches extensively to generate shallow-wide pits, which can be attributed to the fast diffusion kinetics of Cl ⁻ and the lower reaction energy of Br ⁻ in the passivation layer. Additionally, for the Ni-based electrodes with catalysts (e.g., NiFe-LDH) loading on the surface, Br ⁻ causes extensive spalling of the catalyst layer, resulting in rapid performance degradation. This work clearly points out that, in addition to anti-Cl ⁻ corrosion, designing anti-Br ⁻ corrosion anodes is even more crucial for future application of seawater electrolysis.

Abstract

It is known that chloride anions cause severe anode corrosion during seawater electrolysis. Here we found that bromide in seawater is even more harmful to Ni-based anodes, causing the spalling of the catalyst layer and the formation of shallow-wide pits on the substrate, leading to performance degradation.