Urea treatment of nitrogen-doped carbon leads to enhanced performance for the oxygen reduction reaction

Manufacturing of advanced functional materials should also rely on the green chemistry principles like utilization of natural renewable resources. Marine environment offers plenty of renewable raw materials like chitin and its derivative chitosan. The paper presents how urea treatment has influenced several textural, chemical, and electrocatalytic properties of N-doped activated carbons (N_ACs) obtained from chitosan and chitin. The materials were subjected to an activation procedure (with different activators) as well as nitrogenation by premixing the precursors with water solutions of urea. Raw and premixed precursors were carbonized in the temperature range of 700–800 °C. The urea treatment resulted in a spectacular increase in the nitrogen content by weight (up to 68%) and an improvement of the surface area (up to 42%) along with total/micro-/mezo-pore volume (up to 49%). Some urea-modified N_ACs were capable of reducing oxygen in an alkaline solution as effectively as a Pt-loaded carbon material. The highest number of electrons transferred to O2 molecule was found to be equal to 3.76 for a chitosan derived sample. This ability of chitosan and chitin derived N-rich activated carbons was studied by means of the method named rotating ring disc electrode.