Legume root nodule derived porous carbon materials through the in situ ZIF-8 activation strategy

Abstract

The utilization of harsh chemicals is obligatory during the preparation of biomass-derived carbon materials. ZIF-8 serves as a zinc-based metal–organic framework (MOF), in which the internal zinc ions (Zn²⁺) are reduced to metallic Zn during high-temperature pyrolysis, which then evaporates and etches the carbon skeleton, significantly increasing the specific surface area and porosity of the material. In the current work, the ZIF-8 and the legume root nodules were used as an activator and biomass precursors to develop a more atom-economical and eco-friendly strategy for the preparation of porous carbon materials. The roles the ZIF-8 and the species of legume root nodules play in the structure and performance of the final carbon materials were well explored and discussed. The specific surface area of our optimal carbon RW@Z8(5) is up to 1459.27 m² g⁻¹. The catalyst RW@Z8(5) was employed in fuel cells for the oxygen reduction reaction (ORR) and demonstrated a half-wave potential (E_1/2) of 0.720 V (vs. RHE) in 0.1 M HClO₄, which is only 88 mV lower than that of the Pt/C catalyst. Our results prove the possibility of the metal–organic framework (MOF) activation strategy for the development of biomass-derived porous carbon materials.