Influence of Different Pore‐Forming Agents on Electrochemical Performance of Iron Electrodes

ABSTRACT Practical application of iron‐air batteries (IABs) remains constrained by the low charging efficiency and poor discharge rates of iron electrodes. Hydrogen evolution reaction (HER) occurring on the iron electrode and anodic passivation reaction of the electrode itself are the primary factors contributing to the poor cycling stability and capacity degradation of IABs. Herein, stability of iron electrodes is enhanced by modifying their microstructure to alter electrochemical performance. K 2 CO 3 , (NH 4 ) 2 CO 3 , KCl, and carbon nanotubes (CNTs) are used as pore‐forming agents during the preparation of iron electrodes. Subsequent hot‐pressing and hot‐water soaking treatments yield corresponding iron electrodes Fe‐K 2 CO 3 /NF, Fe‐(NH 4 ) 2 CO 3 /NF, Fe‐KCl/NF and Fe‐CNT/NF, which display distinct microstructures. Hydrogen evolution reaction and iron anodic passivation process on these iron electrodes are investigated, with their electrochemical active surface area (ECSA) measured via cyclic voltammetry. In addition to exhibiting outstanding suppression performance for anodic passivation, Fe‐CNT/NF also shows the smallest HER current density in the range of 0 ~ 125 mA⋅cm −2 . The iron‐air battery using Fe‐CNT/NF as the iron electrode and Pt/C + IrO 2 as the air electrode demonstrates favorable charge–discharge efficiency and stability, characterized by a voltage efficiency of 54.5% and discharge voltage of 0.8 V. Results reveal that the microstructure constructed with CNTs can effectively improve the electrochemical charge/discharge cycling performance of iron electrodes.