Laser-induced carbonization of MnO2–bioresin composites for stable air cathodes in alkaline Zn–air batteries

Laser conversion of polymers into high surface area conductive electrodes offers a furnace-free route to simultaneously form carbon supports and embed electrocatalysts. While laser-induced graphene (LIG) has been decorated with catalysts via post-processing, the influence of embedding catalyst precursors directly within the polymer on phase conversion and electrochemical performance has been far less explored. Herein, we investigated the laser conversion of polyfurfuryl alcohol, a biomass-derived resin, loaded with manganese dioxide (MnO₂). Lasing consistently produced a mixed-phase MnO₂/Mn₃O₄/MnO structure uniformly embedded within conductive carbon (LIG/Mn_xO_y). Ball milling of the MnO₂ precursor reduced the particle size, increased retention of catalytically active Mn³⁺ species, and promoted a dominant four-electron oxygen reduction reaction pathway with a lower peroxide yield. Performance increased with loading up to an optimal 5 wt% milled MnO₂, which exhibited the highest ORR activity. When incorporated into zinc–air batteries, these electrodes delivered power density comparable to Pt/C (20 wt%) and significantly enhanced the cycling stability relative to composites made by physically mixing carbon black with untreated MnO₂, underscoring the benefits of laser-assisted embedding.