Fe-Rich\nNi_0.06Fe_0.94OOH Nanorods\nas Efficient Electrocatalysts for the Oxygen Evolution Reaction

Abstract

Developing\nFe-rich oxygen evolution reaction (OER) electrocatalysts\nhas remained a challenge due to the structural rigidity of the phases.\nHowever, wide distribution of the Fe source around the globe and inexpensiveness\ncompared to other transition metals (Ni, Co, etc.) make their development\na priority in electrocatalysis research. Herein, we report the synthesis\nof a Fe-rich OER electrocatalyst (Ni_0.06Fe_0.94OOH) that operates at significantly higher efficiency compared to\nNi-rich materials. A controlled synthesis using polyethylenimine as\na capping agent was adapted, which rendered FeOOH nanorods with excellent\ncolloidal stability. Incorporation of a minuscule amount (6%) of Ni­(II)\nin the material resulted in the dramatic enhancement of geometric\nOER activity compared to Ni-rich phases. The Ni_0.06Fe_0.94OOH catalyst possesses a low overpotential of 287 ±\n9 mV compared to FeOOH, which required 495 ± 8 mV to reach the\nbenchmark current density of 10 mA/cm². The catalyst displayed\na low Tafel slope of 69 mV/dec and high selectivity with a Faradaic\nefficiency of 92%. The catalyst was stable for 2000 cycles of CV performed\nat a scan rate 10 mV/s, and a steady potential response was generated\nfor 24 h at a 100 mA/cm² current density.