Toward Process-Resilient Lignin-Derived Activated Carbons for Hydrogen Storage Applications

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