Evaluation of NiFe Bifunctional Electrocatalysts for Rechargeable Sodium‐Ion‐Based Seawater Batteries

Rechargeable sodium‐based seawater batteries (SWBs) that store energy in the form of metallic Na at the anode require cathodes laden with bifunctional electrocatalysts that can efficiently perform the otherwise kinetically sluggish oxygen evolution (OER) and reduction reactions (ORR). Here, we report the systematic evaluation of NiFe layered double hydroxides (NiFe‐LDHs) as suitable bifunctional electrocatalysts for use in rechargeable SWBs. NiFe‐LDHs with various Ni/Fe ratios were synthesized using a hydrothermal approach to ensure spherical particle morphologies comprising of flowerlike nanosheets pattern on the surface with high surface area of ~63 m ² /g. The electrocatalytic activities and operational stabilities of these synthesized catalysts were evaluated using linear sweep voltammetry and chronopotentiometry in both simulated seawater and natural seawater. The LDH catalysts evaluated in our study showed comparable catalytic behavior in simulated seawater, whereas in natural seawater, performances drastically varied. Additionally, the best performing catalyst was tested in a dual compartment Na seawater cell, demonstrating successful sequential OER and ORR operation in natural seawater. Overall, this study highlights the potential of NiFe‐LDH bifunctional electrocatalysts for rechargeable Na‐based seawater batteries and elucidates the feasibility and design parameters of such catalysts for effective OER and ORR activity in conditions employing natural seawater in SWBs.