One-step spontaneous growth of NiFe layered double hydroxide at room temperature for seawater oxygen evolution

Electrochemical seawater splitting is a promising technique because it addresses two major challenges, clean energy production and seawater desalination, at the same time. Therefore, seeking out a facile and cost-effective way to synthesize highly active and stable seawater-splitting catalysts is of great interest to both the research community and industry. Here we developed an Fe2+-driven, one-step, and spontaneous fabrication method for a seawater-oxygen-evolution-active NiFe layered double hydroxide (LDH) at room temperature. The NiFe LDH was found to exhibit very high activity and stability toward the oxygen evolution reaction (OER) in an alkaline natural seawater electrolyte, delivering current densities of 100 and 500 mA/cm2 at low overpotentials of 247 and 296 mV, respectively, and with no significant degradation observed over long-term stability testing of 96 h under a large current density of 500 mA/cm2 in 1 M KOH seawater electrolyte. After coupling with a good hydrogen evolution reaction (HER) catalyst, NiMoN, the two-electrode electrolyzer was found to achieve current densities of 10, 100, and 500 mA/cm2 at voltages of 1.477, 1.533, and 1.665 V, respectively, in alkaline natural seawater with good durability over 100 h at 500 mA/cm2. The oxidation of Fe2+ is the driving force for the growth of NiFe LDH, and this mechanism is universal to the fabrication of other Fe-based hydroxides as efficient OER catalysts.