Free-standing single-crystalline NiFe-hydroxide nanoflake arrays: a self-activated and robust electrocatalyst for oxygen evolution

Free-standing single-crystalline NiFe-hydroxide nanoflake arrays grown in situ on nickel foam are synthesized using a simple hydrothermal method and they exhibit remarkable activity and durability for oxygen evolution in 1.0 M KOH, achieving a decreased over-potential of 235 mV to produce 10 mA cm(-2) current density after long-term operation up to 100 h.