Cost-effective and efficient water and urea oxidation catalysis using nickel-iron oxyhydroxide nanosheets synthesized...

The synthesis of earth-abundant, low-cost, and stable electrocatalysts with high efficiency in the oxygen evolution reaction (OER) is a necessary requirement for improving the effectiveness of electrochemical water splitting approach. To date, expensive electrode materials and time-consuming synthesis procedures have generally been used for the electrocatalysts applied in water splitting, which limits their efficiency. Herein, nickel-iron oxyhydroxide nanosheets are fabricated by a scalable and ultrafast (requiring only 5 s) wet chemical strategy on a nickel foam substrate. The experimental results indicate that compared to recently reported catalysts, the prepared nickel-iron oxyhydroxide electrode has a high number of active sites and low reaction barrier, enabling efficient OER catalysis in an alkaline electrolyte. In particular, the prepared nickel-iron oxyhydroxide electrode requires an ultralow overpotential of 230 mV to reach a current density of 50 mA cm^-2, with excellent long-term stability for 75 h. Moreover, the nickel-iron oxyhydroxide also performs well towards the electrocatalytic urea oxidation reaction (UEOR), with a very low potential of 1.38 and 1.41 V vs RHE (reversible hydrogen electrode) to reach 50 and 100 mA cm^-2 current density in 1 M KOH with 0.33 M urea electrolyte. This ultrafast synthesis approach can be extended to prepare electrocatalysts used for other electrochemical reactions.