Lignin-derived hierarchical porous flower-like carbon nanosheets decorated with biomass carbon quantum dots for efficient oxygen reduction

Abstract

Excavating and developing efficient and economical non-metallic nanomaterial catalysts for oxygen reduction reactions (ORR), which are vital for fuel cells, but is still challenging. Here, we synthesize a nitrogen-doped hierarchical porous flower-like carbon nanosheets decorated with nitrogen-doped carbon quantum dots. The hierarchically porosity heteroatom-doped flower-like carbon nanosheets are first synthesized using MgO as hard template, KOH/NaOH as activator, lignin/urea as carbon/heteroatom source, and then lignin-based carbon quantum dots (CQDs) fabricated via microwave hydrothermal are compounded with carbon nanosheets after a one-step hydrothermal treatment. Benefitting from the interconnection of its 3D graphite shell network, abundant active sites, high specific surface area, and multi-scale pore structure, the n-HPFN@CQDs exhibits favorable ORR activity and stability in 0.1 mol KOH media. Compared with commercial Pt/C, the assembled Zn-air batteries using n-HPFN@CQDs as electrode catalysts exhibit comparable discharge performance. This work synthesized a novel and green biomass-based carbon composite materials achieving high-performance for energy conversion applications.