Janus carbonaceous assembly of biomimetic wettability-gradient air electrode for optimizing zinc-air battery kinetics

Optimizing the architecture of air electrodes is pivotal for improving reaction kinetics and structural stability in zinc-air batteries (ZABs), yet balancing these enhancements with cost-effective fabrication remains a challenge. Herein, a facile biomimetic assembly strategy is proposed to construct an asymmetric air electrode with Janus carbonaceous architecture and wettability gradient. Two components, which are functionalized graphene nanosheets (FGNSs) and carbon nanotubes (FCNTs) both anchoring iron phthalocyanine for oxygen reduction catalysis, are employed as building blocks. The former assemble into fish-scale-like hydrophilic lamellar structure facing the electrolyte, facilitating swift ion infiltration; while the latter arrange into waterspider-leg-like hydrophobic villus structure exposed to ambient air, enhancing rapid oxygen invasion. This asymmetric design (Asy-FCNTs-FGNSs) not only boosts mass transport and expands triple-phase boundary, but also improves structural robustness of the air electrode. The resulting ZAB achieves a high peak power density of 239.3 mW cm^-2 and a specific capacity of 814.3 mAh g_Zn^-1 (10 mA cm^-2), along with outstanding cycling stability, overwhelmingly outperforming conventional symmetric counterparts and prior self-supporting designs. This work presents an innovative architecture-optimization scheme for advanced air electrodes, offering a scalable bioinspired strategy to propel ZAB technology and guide future electrode advancements.