Fluorine-doped nickel oxyhydroxide as a robust electrocatalyst for oxygen evolution reaction

Fluorine (F) anion doping has recently emerged as a promising approach for boosting the activity of earth-abundant metal catalysts for the oxygen evolution reaction (OER). But many key questions concerning this new approach remain unanswered, including the nature of F-doping, the mechanistic understanding of F-doping effects as well as the long-term stability of F-doped catalysts. Herein, we report a case study of F-NiOOH/Ni(OH)2/NF catalyst that was fabricated using a simple anodic electrooxidation method in a F-containing alkaline solution. A combination of experimental and computational studies revealed that F anions substitute for OH groups in the NiOOH surface layer and such a substitutional F-doping results in significant improvement of OER activity. In particular, the F-doped catalyst possesses outstanding stability when operated in a F-containing electrolyte. For instance, F-NiOOH/Ni(OH)2/NF showed an overpotential fluctuation of only ±4 mV in a 100-h constant current test at 100 mA cm−2 in a 0.01 M KF alkaline solution. Furthermore, our study found that this simple F-doping method is applicable to other transition metal oxide/hydroxide catalysts for boosting OER activity.