Boosting ORR Electrocatalytic Performance of Metal-Free Mesoporous Biomass Carbon by Synergism of Huge Specific Surface Area and Ultrahigh Pyridinic Nitrogen Doping

Abstract

Oxygen reduction reaction (ORR) plays a critical position in direct methanol fuel cells. However, electrocatalytic materials currently utilized in ORR use a rare and expensive metal Pt, so it is vital to develop cathode catalysts with cheap and high ORR activity. Herein, chitosan, a natural material made from chitin, was employed as a complex precursor of carbon source and nitrogen (N) source to synthesize N-doped mesoporous biomass carbon ORR catalysts. Adding different pore agents regulated specific surface area and N type of catalysts. The relationship between the properties of the catalysts and their ORR electrocatalytic performance was investigated. It was luckily found that the addition of ferric nitrate as a pore-forming agent created a huge specific surface area of the N-doped mesoporous biomass carbon (1190 m2/g) significantly. More importantly, the synthesized catalyst was doped by whole pyridinic-N at high content (11.58 at %) and inhibited the two-electron reaction efficiently, promoted the four-electron reaction, and accelerated the ORR reaction rate. Furthermore, it provided significant catalytic activity with robust methanol tolerance, and notable cycle stability, indicating the practical applicability of the huge surface area, ultrahigh pyridinic-N-doped mesoporous biomass carbon catalyst.