Dual-Doping Fe-Ni Oxide for Ultrahigh Performance Seawater Oxidation by High-Concentration Electrolytes

Abstract

Inhibiting the chlorine evolution reaction is of great significance for the design and development of oxygen evolution catalysts with high current density for seawater electrolysis. The concentration of KOH concentration plays a very important role in controlling the chlorine evolution potential in seawater electrolysis. However, the effect of potassium hydroxide concentration, especially under high concentration of KOH (>1 M), on the oxygen evolution activity of different catalysts has not been studied so far. Here, we found that the concentration of potassium hydroxide has a different linear effect on the oxygen evolution activity of different catalysts, and we first propose the concentration activity coefficient (CAC) to express the linear relationship between the oxygen evolution activity of the catalyst and the KOH concentration in seawater electrolysis. Based on CAC, we report a Co S-NiFe2O4 catalyst with ultrahigh oxygen evolution activity under 3M potassium hydroxide concentration seawater. At current densities of 500 mA cm-2 and 1000 mA cm-2, the overpotentials of Co S-NiFe2O4 are 270 mV, and 287 mV, respectively, which are much lower than those of the existing electrocatalysts. More promising, the new catalysts also showed a Tafel slope of 18.8 mV dec-1 and a long catalytic lifetime in high concentration alkaline electrolyte. Our findings provide a better understanding of the correlation between KOH concentration and electrocatalytic activity and open new avenues for design and development of electrocatalysts for the next generation of high OER activity in seawater electrolysis.

Keywords: oxygen evolution