Mechanochemically driven iodination of activated charcoal for metal-free electrocatalyst for fuel cells and hybrid Li-air cells

Iodination of carbon-based materials is known to improve their electrocatalytic activity for oxygen reduction reaction. Here, we report iodination of activated charcoal by mechanochemical ball-milling activated charcoal (AcC) in the presence of iodine (I2). The electrodes fabricated from the resultant iodinated AcC (IAcC) show efficient metal-free electrocatalytic activity for fuel cells and hybrid Li-air cells. In addition to iodination, the ball-milling can not only purify AcC but also change morphology. The iodine content in IAcC reaches as high as 0.59 at.% (5.8 wt.%), the amorphous powder-type morphology of the starting AcC has been changed to the flake-type sheets of the resulting IAcC, and metallic impurities in the IAcC are substantially reduced. The results indicate that the mechanochemical ball-milling simultaneously induces functionalization, structural restoration and purification. Furthermore, the IAcC is readily dispersible in various polar solvents, allowing the fabrication of electrodes via solution processing. The metal-free IAcC cathodes exhibited outstanding electrocatalytic activities for fuel cells and hybrid Li-air cells with higher selectivity, longer-term stability and better tolerance to methanol crossover/CO poisoning effects than the starting AcC and comparable with commercial Pt/C counterparts.