The production of carbon microtubes by the carbonization of catkins and their use in the oxygen reduction reaction

Willow or poplar catkins were carbonized to prepare carbon microtubes (CMTs) due to their natural micro-tubular structure. After carbonization at temperatures of 550–950 °C, CMTs with outer and inner diameters of 4–8 and 3–7 μm were obtained. In addition to having a large and accessible inner tube, a small amount of nitrogen (∼1.8 at.%) and phosphorus (∼0.4 at.%) dopants cause CMTs prepared at 750 °C to be a cheap metal-free catalyst with good catalytic activity in the oxygen reduction reaction.