Facile modulation of hierarchical structures in biomass-derived carbon via metal–organic framework-mediated assembly for enhanced oxygen and carbon dioxide reduction reactions

Rationally modulating the hierarchical structure of biomass-derived carbon while ensuring developed pore structure and effective doping is imperative for its high-value utilization, but remains challenging. Herein, a three-dimensional (3D) hierarchical flower-like carbon with high surface area and N-doping was synthesized through a directed assembly and carbonization strategy, where biomass serves as a template and support during zeolitic imidazolate framework-8 (ZIF-8) precursors self-assembly. Benefiting from the regularity and abundant porosity of flower-like structure, and unique electronic properties by nitrogen-doping, the flower-like carbon possesses more exposed and heteroatom homogeneously distributed active surface, thus exhibiting oxygen reduction reaction (ORR) activity comparable to that of commercial Pt/C catalysts. Theoretical calculation results reveal that this ordered N-doped carbon lowers the reaction free energy and improves its ORR activity. In addition to being directly used for ORR, the flower-like carbon is also suitable as a substrate for dispersed Ni-doping in CO₂ electroreduction. The prepared Ni-doped flower-like carbon exhibits superior CO Faraday efficiency (91%) and long-term stability (48 h) compared to other Ni-doped carbons. This work may provide insights into constructing biomass-derived carbon with tailored hierarchical structures for diverse energy-related applications.