Synergetic design of dopant-free defect-enriched 3D interconnected hierarchical porous graphene mesh for boosting oxygen reduction reaction

To resolve Pt-dependency problems in energy convention systems, we provide an idea for construct a highly active 3D interconnected hierarchical porous graphene mesh (3D-PGM) with effective exposure active sites. By a facile controllable process through self-assembly and chemical etching of reduced-graphene oxide, synergetic enhancement of oxygen reduction reaction (ORR) performance from intrinsic activity to apparent activity was realized. The as-obtained materials exhibit 3D interconnected hierarchical porosity for efficient mass transport, a high surface defect content with increased numbers of active sites and a robust conductive network, leading to a comprehensive multiscale electron transfer capability that ultimately enhances the ORR catalytic activity. Incredibly, the alkaline ORR performance of as-obtained catalyst exhibits a 4-electron pathway reaction with an onset potential (Eonset) of 0.89 V, half-wave potential (E1/2) of 0.84 V, and a lower Tafel slope of 58 mV dec−1, showing activity comparable to that of Pt/C catalysts. Moreover, the as assembled primary Zn–air batteries (ZABs) demonstrate a higher power density (182.6 mW cm−2) and a higher specific capacity (809.1 mA h g−1) than the Pt/C-based counterpart. The outstanding electrochemical performance and facile fabrication techniques make this material a promising alternative to commercial Pt/C for renewable energy devices.