High hydrogen storage capacity of heteroatom-containing porous carbon nanospheres produced from cross-linked polyphosphazene nanospheres

Heteroatom-containing porous carbon nanospheres were fabricated by forming polyphosphazene nanospheres and carbonizing them with NaOH as activating agent. They were then examined as a material for hydrogen storage. N2 sorption and H2 sorption measurements showed that the carbon nanospheres possess a BET surface area of 1140 m2 g− 1, a total pore volume of 0.90 m3 g− 1, an ultramicropore volume of 0.30 m3 g− 1, a bimodal pore size distribution (3–5 nm and 0.6–0.8 nm diameter pores), and a gravimetric hydrogen uptake of 2.7 wt.% at 77 k and 1 atm.

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► Polyphosphazene nanospheres were used as carbon precursors.
► The carbon nanospheres possess a large surface area and a bimodal pore size distribution.
► Small amounts of heteroatoms such as N, O, P, and S were doped in carbon nanospheres.
► The carbon nanospheres exhibit a high hydrogen uptake of 2.7 wt.% at 77 k and 1 atm.