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.