Nitrogen and Phosphorus Modification to Enhance the Catalytic Activity of Biomass-Derived Carbon toward Oxygen Reduction Reaction

As the crucial cathode reaction of fuel cells and metal-air battery, oxygen reduction reaction (ORR) has always required a kind of catalyst to improve electrochemical reaction rate. In this article, taking Fructus azedarach as raw material, a nitrogen-phosphorus double-doped carbon nanosheet material was synthesized through microwave-assisted hydrothermal treatment and calcination. The synthesized amorphous NPDC possessed multi-level pores and abundant edge defects. With a N: P of 1.09, doped N, P achieved the best electronic synergistic effect and thus caused surrounding carbon to show high catalytic activity towards ORR with a half-wave potential of 0.84 V, onset potential of 0.94 V and limiting current density value of 6.01 mA•cm−2 in alkaline media. The NPDC-1.09 also exhibited superior stability (drop of 11 % at 0.8 V after 22 h) and methanol tolerance (3.2 % decline) compared to 20 % Pt/C. When used in zinc-air battery, its promising application in the field of energy storage and conversion is demonstrated by the 84 h long-term cycling stability (with a current density of 10 mA•cm−2). The discovery of such N, P dual-doped carbon structure with substantial synergistic effect is of great significance for promoting the replacement of platinum-based catalysts with carbon-based materials.