Rigid large-inner-diameter (> 15.0 nm) multiwalled carbon nanotubes (LID-MWCNTs) were synthesized from cetyltrimethylammonium bromide (CTAB) and ammonium metatungstate, in which CTAB was converted to CNT structure and ammonium metatungstate was converted to WC nanoparticles inside of LID-MWCNTs.