posted on 2023-12-11, 15:20authored byXue Gao, Long Hu, Yuchen Mao, Zeming Zhong, Liangjun Huang, Kaisheng Xia, Hui Wang, Min Zhu
Porous
carbon materials (PCMs) hold great promise as hydrogen storage
materials due to their high capacity but are limited by adsorbing
H2 at either cryogenic temperature or very high H2 pressure due to their weak van der Waals forces with the H2 molecules. In this study, N-doped hierarchical porous carbon (NHPC)
materials were prepared by a simple one-step chemical activation method.
Experimental results reveal that N-doping significantly enhances the
interaction between H2 and the PCMs, which is demonstrated
by increased adsorption isosteric heat (Qst) and H2 storage capacity per specific surface area (SSA).
At lower H2 coverage, the Qst increases from 7.45 kJ/mol (NHPC-0) to 7.95 kJ/mol (NHPC-2 and NHPC-3),
which aligns with the enhanced gravimetric H2 uptake per
SSA. At higher H2 coverage (77 K, 50 bar-H2),
there is a notable enhancement in the volumetric H2 uptake
per SSA for NHPC-3 (11.41 g·L–1/m2·g–1) compared to that for NHPC-0 (8.49 g·L–1/m2·g–1) as the
N content increases. Furthermore, N-doping can increase the packing
density, thereby improving the volumetric H2 storage capacity
of NHPC-x. The enhancement is strikingly demonstrated
by NHPC-2, which achieves a volumetric H2 uptake of 26.96
g/L (SSA = 2458.44 m2/g) at 77 K and 50 bar. This is almost
the same as that for NHPC-0, despite a 21% reduction in SSA, which
is 26.47 g/L (SSA = 3116.58 m2/g) at the same condition.
This work contributes to a deeper understanding of the effect of heteroatom
doping on the H2 storage performance in PCMs.