Enhanced electrocatalytic reduction of oxygen at CO2-derived Fe-N-B-doped porous carbon

Abstract

Fe-N-B doped carbon catalysts are synthesized directly from flue gas containing CO2. They showed enhanced activity for oxygen reduction reaction in an alkaline electrolyte (1 M NaOH), which is comparable activity of commercial platinum catalysts. The amorphous carbon contains nitrogen species derived from nitrogen gas in flue gas and boron atoms which were originated from the reducing agent of sodium borohydride for the flue gas conversion. The amounts of iron species was controlled from 5% to 55% of synthesized amorphous carbon from flue gas. The sample with 33% of Fe precursor species shows the highest oxygen reduction reaction activity. This is due to the existence of pyridinic nitrogen doping and Fe-N bonding in the carbon network verified by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) analyses. Also, from the microscopic images, the degradation of oxygen reduction reaction activity comes from agglomeration of Fe species. The Fe-N-B-C catalyst shows the promise of stability in acidic conditions and long-term durability for 10,000 cyclic voltammetric cycles.