Ammonia assisted regulation of nitrogen-type in carbonaceous support applied for oxygen reduction reaction

Doping Nitrogen in carbon is crucial to modulate its catalytic performance. However, the configuration of doped nitrogen is hard to regulate. In this work, an ammonia assisted in-situ pyrolysis method was proposed to regulate the type of N in N-doped porous carbon supported Co₃O₄ prepared based on the Schiff base reaction between glucose and urea. XPS and FT-IR spectra found that ammonia affects the percentage of C = N formed between glucose and urea during hydrothermal process. The formed C = N not only exhibits strong coordination ability to cobalt ions, but also affects the types of nitrogen in the obtained Co₃O₄/NPC. As a result, the obtained Co₃O₄/NPC with addition of 2 mL ammonia presents an increased percentage of pyridinic-N combined with homogeneously dispersed Co₃O₄. In addition, the decomposition of unstable nitrogen species during pyrolysis creates oxygen vacancy in Co₃O₄ as well as generats pores in the carbonaceous support. Hence, Co₃O₄/NPC-2 exhibits favorable catalytic performance with half-wave potential of 0.83 V and kinetic current density of 10.25 mA cm⁻² @ 0.8 V in comparison with those of Co₃O₄/NPC-0 (0.80 V, 4.42 mA cm⁻² @ 0.8 V). Therefore, this work provides a new strategy for regulating the configuration of nitrogen in carbon-based composite catalyst.