Unveiling the hidden intrinsic porosity of marine biomass-derived carbon: Eliminating pore-blocking minerals

In the context of carbon neutrality, marine biomass (MB) is expected as a potential precursor to replace traditional carbon sources. In this study, we tried to develop an economic pathway to obtain porous carbon materials from MB. A simple pyrolysis of MB gave MB-based carbon (MBC) having a negligible open-pore structure, while after the water washing, it turned to be porous. The results of N2 adsorption tests revealed that the total pore volume and specific surface area of MBC were significantly influenced by both the pyrolysis temperature and the washing method. While MBC was inherently porous due to a catalytic activation function of innate elements in MB such as Na, Mg, K, Ca, and Cl, these species also induced a pore blocking effect, rendering the developed pores initially undetectable. After the washing, Na, K, and Cl in MBC were almost completely removed, and thus, a part of the hidden pores became accessible. Moreover, a unique CO2 aeration washing was able to further remove Mg and Ca elements from MBC, giving rise to further increases of specific surface area (> 1000 m2/g) without an addition of extraneous activating agents. Based on the understanding of the dual role of the innate elements of MB, a potential strategy to realize the environmental-friendly porous carbon production was successfully demonstrated.