Table 1. Porous parameters of the samples.

Samples	BET surface area (m2/g)	Langmuir surface area (m2/g)	t-plot external surface area (m2/g)	Pore volume (cm3/g)	Average pore diameter (nm)
HNTs	64.52	62.51	64.52	0.200	12.45
1C-HNTs	60.28	57.15	60.28	0.219	14.56
3C-HNTs	47.14	43.13	47.14	0.146	12.35
5C-HNTs	30.35	28.97	30.35	0.128	16.93
Pd-HNTs	49.07	44.32	49.07	0.182	14.87
Pd-3C-HNTs	32.59	30.08	32.59	0.137	16.78
3C-Pd-HNTs	64.56	59.35	64.56	0.293	18.13