Ordered Nanoporous Nitrogen- and Oxygen-Codoped Carbon Nanospheres as Electrocatalysts for Oxygen-Reduction Reaction in Direct Methanol Fuel Cells

Metal-free carbon materials are currently of considerable interest to researchers because they have a proven ability to catalyze many electrochemical processes. Making such materials with an abundant amount of nanopores and large specific surface area, and thereby a large density of accessible electrochemically active sites, can enhance their catalytic activities. To this end, herein we report three-dimensional (3D) nanoporous metal-free carbon nanospheres (<200 nm in diameter) with oxygen and nitrogen dopant atoms and high surface area that show superior catalytic activity to reduce oxygen. Compared with 40 wt % Pt/C that is obtained from a commercial supplier, these nanospheres electrocatalyze this reaction in 0.1 M KOH electrolyte with a better onset potential and a similar half-potential. We also show that the nanospheres can be successfully applied as electrocatalysts on the cathode electrode of a direct methanol fuel cell, together with PtRu/C electrocatalyst obtained from a commercial source at the anode. With this cell, a high amount of energy at a power density of 20 mW cm–2 at 15 °C is received. Furthermore, the nanospheres can tolerate a possible methanol crossover reaction reasonably well during their operation in the fuel cell.