Fe-engineered Pd metallenes for boosting bifunctional electrocatalysis in zinc-methanol-air hybrid energy systems

The energy efficiency of zinc-methanol-air batteries (ZMABs) is significantly limited by the CO poisoning during the anodic methanol oxidation reaction (MOR) and sluggish kinetics of cathodic oxygen reduction reaction (ORR). Herein, we report the ultrathin PdFe metallenes as high-performance bifunctional electrocatalysts capable of simultaneously facilitating both MOR and ORR, thereby boosting the overall performance of ZMABs. Specially, the as-synthesized PdFe metallenes exhibit outstanding MOR activity, delivering a mass activity 9 times higher and a CO electrooxidation potential 29 mV lower than those of commercial Pd/C. In the case of ORR, PdFe metallenes show a high mass activity of 1.61 A mg^-1 at 0.9 V (vs. RHE), which is 16 times higher than that of the commercial Pd/C. The minimal ORR performance degradation after 10,000 potential cycles demonstrates a good stability. When integrated into ZMABs, the PdFe metallenes enable a high peak power density of 216 mW cm^-2 and a specific capacity of 796 mAh g^-1, along with impressive cycling durability exceeding 134 h.