Luo Jin, Wang Kangjun, Hua Xing, Wang Wang, Li Jun, Zhang Shiming, Chen Shengli
Department of Chemistry, Hubei Key Laboratory of Electrochemical Power Sources, Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), Wuhan University, Wuhan, 430072, China.
Department of Chemical Engineering, Electrochemical Energy Device Engineering Technology Research Center, Shanghai Jiao Tong University, Shanghai, 200240, China.
Small. 2019 Mar;15(11):e1805325. doi: 10.1002/smll.201805325. Epub 2019 Feb 8.
Nitrogen (N)-doped carbons are potential nonprecious metal catalysts to replace Pt for the oxygen reduction reaction (ORR). Pyridinic-N-C is believed to be the most active N group for catalyzing ORR. In this work, using zinc phthalocyanine as a precursor effectively overcomes the serious loss of pyridinic-N, which is commonly regarded as the biggest obstacle to catalytic performance enhancement upon adopting a second pyrolysis process, for the preparation of a 3D porous N-doped carbon framework (NDCF). The results show only ≈14% loss in pyridinic-N proportion in the Zn-containing sample during the second pyrolysis process. In comparison, a loss of ≈72% pyridinic-N occurs for the non-Zn counterpart. The high pyridinic-N proportion, the porous carbon framework produced upon NaCl removal, and the increased mesoporous defects in the second pyrolysis process make the as-prepared catalyst an excellent electrocatalyst for ORR, exhibiting a half-wave potential (E = 0.88 V) up to 33 mV superior to state-of-the-art Pt/C and high four-electron selectivity (n > 3.83) in alkaline solution, which is among the best ORR activities reported for N-doped carbon catalysts. Furthermore, only ≈18 mV degradation in E occurs after an 8000 cycles' accelerating stability test, manifesting the outstanding stability of the as-prepared catalyst.
氮（N）掺杂碳是有望替代铂用于氧还原反应（ORR）的非贵金属催化剂。吡啶型N-C被认为是催化ORR活性最高的N基团。在本工作中，以锌酞菁为前驱体有效地克服了吡啶型N的严重损失，这通常被认为是采用二次热解过程提高催化性能的最大障碍，用于制备三维多孔氮掺杂碳骨架（NDCF）。结果表明，含锌样品在二次热解过程中吡啶型N比例仅损失约14%。相比之下，不含锌的样品吡啶型N损失约72%。高比例的吡啶型N、去除NaCl后产生的多孔碳骨架以及二次热解过程中增加的中孔缺陷，使得所制备的催化剂成为一种优异的ORR电催化剂，在碱性溶液中表现出高达0.88 V的半波电位（E），比目前最先进的Pt/C高出33 mV，且具有高的四电子选择性（n>3.83），这是报道的氮掺杂碳催化剂中最好的ORR活性之一。此外，经过8000次循环的加速稳定性测试后，E仅下降约18 mV，表明所制备催化剂具有出色的稳定性。
