Toward Process-Resilient Lignin-Derived Activated\nCarbons for Hydrogen Storage Applications

Abstract

Activated carbons\nare promising sorbents that have been heavily\ninvestigated for the physisorptive storage of hydrogen. The industrial\nprocess for production of activated carbons is finely tuned and requires\na reliable and uniform feedstock. While the natural biopolymer lignin,\na byproduct of several industries, has received increasing interest\nas a potentially sustainable and inexpensive activated carbon feedstock,\nthe ratio of the three aromatic monomers (S, G, and H) in lignin can\nbe heavily affected by the lignin source and growing conditions. The\naromatic ratio is known to influence the thermal behavior of the polymer,\nwhich could be problematic for production of consistent activated\ncarbons at scale. With the goal of improving the consistency of activated\ncarbons produced from lignins derived from different feedstocks, here\nwe present a route to limiting the influence of lignin feedstock on\nactivated carbon porosity and performance, resulting in a carbonization\nprocess that is resilient to changes in lignin source. Two different\ntypes of organosolv lignin (representing high S-unit content and high\nG-unit content feedstocks) were investigated. Resulting activated\ncarbons exhibited a high surface area (>1000 m²·g^–1) with consistent adsorptive properties and reasonable\nhydrogen uptake of up to 1.8 wt % at 1 bar and −196 °C.\nThese findings indicate that low-temperature carbonization conditions\ncan be used to produce a consistent carbon material using organosolv\nlignins from any source, paving the way for more widespread use of\nlignin in large-scale carbon production.