# Solvent Effects in Biomass-Derived Activated Carbons: New Insights for Their Doping/Functionalization toward Potential Hydrogen Storage Applications

## TL;DR

This study explores how solvents can modify biomass-derived activated carbons for better hydrogen storage without harsh conditions.

## Contribution

The study reveals how solvents like toluene and isopropyl alcohol can enhance microporosity and adsorption efficiency under mild conditions.

## Key findings

- Toluene and isopropyl alcohol treatments improved microporosity and hydrogen storage capacity over time.
- Tetrahydrofuran exposure reduced textural properties and thermal stability due to disruptive conditions.
- Oxygen exposure led to oxygenated functional groups, causing structural instability but aiding framework reordering.

## Abstract

Biomass-derived activated
carbons play an important role in H2 storage applications
since their structural and chemical
properties can be modulated by adjusting the activating methods and
experimental parameters as well as by functionalization with heteroatoms.
However, unfavorable reaction conditions are usually required, which
may compromise the carbonaceous framework, negatively impacting on
the hydrogen storage performance. In this context, this work investigates
the potential modification effects of different solvents on activated
carbons (ACs) under mild conditions, with a focus on structural and
textural rearrangements. ACs were treated, among others, with solvents
such as toluene (TOL), tetrahydrofuran (THF), and isopropyl alcohol
(IPA) at 353 K for a variable amount of time. Structural and textural
analyses revealed that solvents might have a significant impact on
the microporosity, chemical functionalization, and specific surface
area (S
BET) of ACs, thus potentially affecting
their further chemical functionalization. TOL and IPA treatments demonstrated
the solvent's role in framework reorganization, enhancing microporosity
and storage capacity over reaction time. In contrast, THF exposure
led to a decrease in textural properties and thermal stability, attributed
to disruptive reaction conditions above the solvent’s boiling
point. Furthermore, the presence of atmospheric oxygen was found to
induce the formation of oxygenated functional groups in the graphitic
carbon structure, which contributed to structural instability even
if facilitating the framework reordering during prolonged treatments.
Although treated samples exhibited reduced hydrogen uptake compared
to the parent AC, selected treatments with toluene and IPA demonstrated
promising improvements in adsorption efficiency (i.e., H2 uptake/S
BET). This study opens the possibility
of an effective biomass-derived AC modification, without the need
to employ high-energy-consuming thermal treatments, thus maximizing
the potential of greener processes.