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

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.