Macroalgae-derived nitrogen-doped hierarchical porous carbons with high performance for H2 storage and supercapacitors

Abstract

Using biomass as a precursor for N-doped carbons is critical for future energy storage. Herein, macroalgae pollutants of Enteromorpha prolifera were used to obtain N-doped carbons from carbonization and activation after freeze-drying treatment. The pore structure and surface chemistry of carbons can be altered by adjusting the activation conditions with surface areas up to 3345 m² g⁻¹ consisting of hierarchical pores, and rich N (1.5–3.7%) groups, making algae a good choice for N-doped carbons as adsorbents and electrode materials. Significantly, H₂ uptake is high, up to 7.05 wt% at −196 °C and 20 bar, and an exceptional uptake of 2.71 wt% is also observed at 1 bar, among the largest data relative to state-of-art biomass-based carbons. Electrochemical test results confirmed that the carbon with the largest surface area had a capacitance of 440 F g⁻¹ at 1 A g⁻¹ in 6 M KOH electrolyte while the carbon with the largest microporous surface area had good cycling stability with 87% initial capacitance after 5000 cycles due to its hierarchical pores with high surface areas providing many active sites for better facilitating electrolyte diffusion.