Fe-Rich Ni_0.06Fe_0.94OOH Nanorods as Efficient Electrocatalysts for the Oxygen Evolution Reaction

Developing Fe-rich oxygen evolution reaction (OER) electrocatalysts has remained a challenge due to the structural rigidity of the phases. However, wide distribution of the Fe source around the globe and inexpensiveness compared to other transition metals (Ni, Co, etc.) make their development a priority in electrocatalysis research. Herein, we report the synthesis of a Fe-rich OER electrocatalyst (Ni0.06Fe0.94OOH) that operates at significantly higher efficiency compared to Ni-rich materials. A controlled synthesis using polyethylenimine as a capping agent was adapted, which rendered FeOOH nanorods with excellent colloidal stability. Incorporation of a minuscule amount (6%) of Ni(II) in the material resulted in the dramatic enhancement of geometric OER activity compared to Ni-rich phases. The Ni0.06Fe0.94OOH catalyst possesses a low overpotential of 287 ± 9 mV compared to FeOOH, which required 495 ± 8 mV to reach the benchmark current density of 10 mA/cm2. The catalyst displayed a low Tafel slope of 69 mV/dec and high selectivity with a Faradaic efficiency of 92%. The catalyst was stable for 2000 cycles of CV performed at a scan rate 10 mV/s, and a steady potential response was generated for 24 h at a 100 mA/cm2 current density.