Sustainable and Flexible Zn–Air Batteries Enabled by Bifunctional Electrocatalysts Derived From Lemna minor (Duckweed) Biochar

Lemna minor is an aquatic plant with a high growth rate, which can cause problems in freshwater bodies. In this work, Lemna minor was valorized for the development of bifunctional electrocatalysts for rechargeable and flexible zinc–air batteries (FZABs), by synthesizing cobalt‐doped and cobalt–manganese co‐doped electrocatalysts (L‐Co and L‐CoMn). Raman spectroscopy revealed structural disorder, particularly in L‐Co, which was further confirmed by TEM and attributed to a high density of surface defects. Moreover, TEM and STEM imaging indicated the formation of both spinel nanoparticles and atomically dispersed metal sites, which together with surface defects, contributed to the electrocatalytic activity. Electrochemical tests showed that L‐Co exhibited superior activity in the oxygen reduction reaction, while L‐CoMn demonstrated enhanced activity for the oxygen evolution reaction, achieving a low overpotential of 1.56 V at 10 mA cm ⁻² . When used as bifunctional electrocatalysts in FZABs, the L‐Co presented better performance, higher cycling stability (>100 cycles), and improved capability to operate at elevated current densities, while achieving an areal specific capacity of 14.7 mA.h cm ⁻² . These results demonstrate the potential of Lemna minor valorization for applications in electrochemical and sustainable energy technologies.