Microwave-assisted pyrolysis of Pachira aquatica leaves as a catalyst for the oxygen reduction reaction

In this study, biomimetic Mg–N(x)–C(y) from Pachira aquatica leaves were mixed with carbon black (L/C catalyst), in which the mixture was treated by a conventional microwave oven at 700 W and 2 min, exhibiting high catalytic activity for the oxygen reduction reaction (ORR). By using a microwave-assisted process, it not only offers a cheaper and faster way to synthesize the catalyst compared to the conventional furnace process but also avoids the decomposition of the N(4)-structure. Using the optimized conditions, the L/C catalyst exhibits an electron transfer number of 3.90 and an HO(2)(−) yield of only 5% at 0.25 V vs. RHE, which is close to the perfect four electron-transfer pathway. Besides, the L/C catalyst offers superior performance and long-term stability up to 20 000 s. The L/C catalyst contains a high proportion of quaternary-type nitrogen, Mg–N(x)–C(y), and –C–S–C– which can be the active sites for the ORR.