Synthesis of Zr 2 ON 2 via a urea-glass route to modulate the bifunctional catalytic activity of NiFe layered double hydroxide in a rechargeable zinc-air battery

The development of a highly efficient, stable, and low-cost bifunctional catalyst is imperative for facilitating the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, significant challenges are involved in extending its applications to rechargeable zinc-air batteries. This study presents a bifunctional catalyst, Zr 2 ON 2 @NiFe layered double hydroxide (LDH), that was developed by utilizing a urea -glass route for synthesizing the Zr 2 ON 2 precursor, followed by riveting NiFe LDH nanosheets using a hydrothermal method. Specifically, the vertical distribution of NiFe LDH on the Zr 2 ON 2 surface ensures the maximization of the number of accessible active sites and interfacial catalysis of NiFe LDH. Notably, Zr 2 ON 2 @NiFe LDH demonstrates ORR and OER bifunctional electrocatalytic behavior and high stability owing to its heterostructure and composition. Furthermore, a rechargeable zinc-air battery using a Zr 2 ON 2 @NiFe LDH electrocatalyst as the air cathode demonstrated a high peak power density (172 mW cm -2 ) and galvanostatic charge-discharge cycle stability (5 mA cm -2 over 443 h). Thus, this study presents an efficient and cost-effective strategy for the design of bifunctional electrocatalysts.