Effect of fluorine content in layered double hydroxide catalyzing oxygen evolution

Layered double hydroxides (LDHs) have been extensively studied in OER owing to their unique advantages. The mechanism of the effect of NH4F, a common and essential structural guide in the synthesis of LDH, on LDH is relatively ambiguous. Therefore, the solvothermal process synthesized a series of FeCoNi LDHs with different fluorine contents. Physical and chemical characterizations show that the fluorine content regulates the synthesis process, morphology, and electronic structure of the catalysts. The optimal catalyst required 196 mV overpotential to reach 10 mA cm-2, with a Tafel slope of 22 mV dec-1, and stable operation at a current density of 100 mA cm-2 for more than 120 h. XPS analysis demonstrated that the F- ions leached gradually during the OER reaction, promoting the formation of high-valent intermediates at the Co active site to enhance the catalyst activity. This work contributes to the subsequent study of LDH modification and NH4F.