Sulfate-assisted Ni/Fe-based electrodes for anion exchange membrane saline splitting

Saline water electrolysis is an appealing strategy for hydrogen production, attracting more attention in recent years. NiFe-based electrodes exhibit promise as catalysts for saline water electrolysis. Nevertheless, they suffer from the inferior service life of the oxygen evolution reaction (OER). Herein, we report an oxygen-evolution electrode consisting of a sulfate-modulated nickel-iron hydroxide (NiFeOOH) affording as the catalytic active layer and Fe-Ni₃S₂ as the corrosion-proof layer. The developed electrode only requires overpotentials of 220 and 292 mV to deliver the current density of 10 and 500 mA·cm⁻², respectively. More importantly, it presents long-term stability exceeding 140 and 100 h in 1 M KOH at high current densities of 500 and 1000 mA·cm⁻², respectively, as well as 120 h for saline water electrolysis at 100 mA·cm⁻². Experimental results reveal that the generated sulfate plays an indispensable role in improving stability and corrosion resistance. We assembled and tested an anion exchange membrane electrolyzer with Pt/C and NiFeS/NIF as the cathode and anode, respectively, under industrial conditions. This overall water-splitting electrolyzer achieves an impressive energy conversion efficiency of 75% ± 0.5%. This report offers fresh insights into the design of stable NiFe-based electrodes, which may further promote its practical applications for saline water electrolysis.