Achieving durable alkaline seawater oxidation over NiFe layered double hydroxide via sulfur doping
Hua Chen, Mingyu Liu, Zhenju Jiang, Shengjun Sun, Imran Shakir, Yao Li, Xuping Sun
Abstract
Alkaline seawater electrolysis is promising for large-scale production of green hydrogen but the chlorine evolution reaction (CER) causes severe anode’s corrosion under high current densities. This work described the use of a sulfur-doped NiFe layered double hydroxide nanoarray on Ni foam (S-NiFe LDH/NF) synthesized through a two-step hydrothermal process as a durable catalyst for alkaline seawater oxidation. In 1 M KOH + seawater, the S-NiFe LDH/NF anode needs a low overpotential of 345 mV to afford a current density of 1000 mA·cm<sup>−2</sup> and operates stably over 800 h. Sulfate species generated on the catalyst surface, which is evidenced by <em>in situ</em> Raman spectroscopy analysis, electrostatically repel Cl<sup>−</sup> and thus inhibits the CER. Furthermore, the two-electrode system using S-NiFe LDH/NF and Pt/C/NF as the anode and cathode, respectively, requires a cell voltage of 1.90 V to achieve a current density of 100 mA·cm<sup>−2</sup> and maintains stable operation for 1000 h at 500 mA·cm<sup>−2</sup> in alkaline seawater.