Continuous and low-cost synthesis of high-quality multi-walled carbon nanotubes by arc discharge in air

► A continuous and low-cost method for preparing MWCNTs has been developed. ► A horizontal anode and a vertical rotating cathode are used in arc discharge process. ► The cheapest and most accessible air is adopted as the buffer gas. ► MWCNTs are immediately taken out of the arc discharge region. ► The purified MWCNT film shows a good field emission property.