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 N4-structure. Using the optimized conditions, the L/C catalyst exhibits an electron transfer number of 3.90 and an HO2 - 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.