S, N dual-doped porous carbon materials derived from biomass for Na ion storage and O2 electroreduction

Heteroatom-doped porous carbon materials have been widely reported in electrochemistry, but low-cost carbon sources and facile synthesis strategy are still highly in demand. Herein, N, S dual-doped porous carbon materials (CDNSPCs) were synthesized by carbonizing and etching pollution source-carrageenan, which shows great potentials as anodes for sodium-ion batteries (SIBs) and electrocatalysts for oxygen reduction reaction (ORR). Using K-, I- or lambda-type carrageenan as precursor, three carbon samples (CDNSPC-1, -2, or -3) were obtained, respectively. Among them, CDNSPC-3 with the highest sulfur content exhibits an initial discharge capacity of 1505 mAh g(-1) at 0.05 A g(-1), a high specific capacity of 85 mAh g(-1) at 10 A g(-1), and a capacity of 171 mAh g(-1) at 1.0 A g(-1) after 400 cycles. Moreover, it also exhibits excellent ORR activity with relatively positive E-onset (0.88 V vs RHE) and a four-electron dominant pathway, much better than CDNSPC-1 and CDNSPC-2. The high sulfur content in the precursor could efficiently promote the activation by combining metal ions of activating agents and sulfur-containing groups at high temperature. The present strategy is low-cost and eco-friendly, opening a new avenue for the sustainable development of valuable materials from pollutants.