Highly porous defective carbons derived from seaweed biomass as efficient electrocatalysts for oxygen reduction in both alkaline and acidic media

In this work, we report a series of defective carbon catalysts prepared through a facile and scalable “N-doping-removal” process using seaweed biomass sodium alginate (SA) as precursor. Our systematic studies reveal that the defect content, porosity characteristic and conductivity of defective carbons can be finely tuned by manipulating the pyrolysis temperature and viscosity of precursor polymer SA, which significantly affect the ORR performance. The optimized defective porous carbon catalyst (i.e., D-PC-1(900)) that was revealed to possess abundant ORR-active defects, large surface area of 1377 m2g-1, abundant hierarchical porosity and good conductivity, exhibited very nice ORR activity and selectivity in 0.1 M KOH, comparable to the commercial Pt/C catalyst. In 0.5 M H2SO4, considerable ORR activity was also observed for D-PC-1(900), which is among the highest reported for defective carbons and comparable to many of N-doped carbons. Density functional theory calculations indicate that the carbon defect can create the active sites for ORR in acidic media. More importantly, in both alkaline and acidic media, D-PC-1(900) shows much better stability and methanol tolerance than those of the Pt/C catalyst. All these results demonstrate that the seaweed biomass derived defective carbon is an excellent candidate for non-precious-metal ORR catalyst in various fuel cells.